E3 ubiquitin-protein ligase, which catalyzes ubiquitination of target proteins together with ubiquitin-conjugating enzyme E2 UBE2L3. Acts as an atypical E3 ubiquitin-protein ligase by working together with cullin-RING ubiquitin ligase (CRL) complexes and initiating ubiquitination of CRL substrates: associates with CRL complexes and specifically mediates addition of the first ubiquitin on CRLs targets. The initial ubiquitin is then elongated by CDC34/UBE2R1 and UBE2R2. E3 ubiquitin-protein ligase activity is activated upon binding to neddylated cullin-RING ubiquitin ligase complexes. Plays a role in protein translation in response to DNA damage by mediating ubiquitination of EIF4E2, the consequences of EIF4E2 ubiquitination are however unclear. According to a report, EIF4E2 ubiquitination leads to promote EIF4E2 cap-binding and protein translation arrest. According to another report EIF4E2 ubiquitination leads to its subsequent degradation. Acts as the ligase involved in ISGylation of EIF4E2.

TY - JOUR. T1 - Muscle RING finger-1 promotes a maladaptive phenotype in chronic hypoxia-induced right ventricular remodeling. AU - Campen, Matthew J.. AU - Paffett, Michael L.. AU - Colombo, E. Sage. AU - Lucas, Selita N.. AU - Anderson, Tamara. AU - Nysus, Monique. AU - Norenberg, Jeffrey P.. AU - Gershman, Ben. AU - Hesterman, Jacob. AU - Hoppin, Jack. AU - Willis, Monte. PY - 2014/5/8. Y1 - 2014/5/8. N2 - Exposure to chronic hypoxia (CH) induces elevated pulmonary artery pressure/resistance, leading to an eventual maladaptive right ventricular hypertrophy (RVH). Muscle RING finger-1 (MuRF1) is a muscle-specific ubiquitin ligase that mediates myocyte atrophy and has been shown to play a role in left ventricular hypertrophy and altered cardiac bioenergetics in pressure overloaded hearts. However, little is known about the contribution of MuRF1 impacting RVH in the setting of CH. Therefore, we hypothesized that MuRF1 deletion would enhance RVH compared to their wild-type littermates, while ...

TY - JOUR. T1 - The ubiquitin-conjugating enzyme UBCH7 acts as a coactivator for steroid hormone receptors. AU - Verma, Seema. AU - Ismail, Ayesha. AU - Gao, Xiuhua. AU - Fu, Guilian. AU - Li, Xiaotao. AU - OMalley, Bert W.. AU - Nawaz, Zafar. PY - 2004/10/1. Y1 - 2004/10/1. N2 - We investigated the role of the ubiquitin-conjugating enzyme UBCH7 in nuclear receptor transactivation. Using transient transfection assays, we demonstrated that UBCH7 modulates the transcriptional activity of progesterone receptor (PR) and glucocorticoid, androgen, and retinoic acid receptors in a hormone-dependent manner and that the ubiquitin conjugation activity of UBCH7 is required for its ability to potentiate transactivation by steroid hormone receptors (SHR). However, UBCH7 showed no significant effect on the transactivation functions of p53 and VP-16 activation domain. Depletion of endogenous UBCH7 protein by small interfering RNAs suggests that UBCH7 is required for the proper function of SHR. Furthermore, a ...

TY - JOUR. T1 - Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome. AU - Berg, E. L.. AU - Pride, M. C.. AU - Petkova, S. P.. AU - Lee, R. D.. AU - Copping, N. A.. AU - Shen, Y.. AU - Adhikari, A.. AU - Fenton, T. A.. AU - Pedersen, L. R.. AU - Noakes, L. S.. AU - Nieman, B. J.. AU - Lerch, J. P.. AU - Harris, S.. AU - Born, H. A.. AU - Peters, M. M.. AU - Deng, P.. AU - Cameron, D. L.. AU - Fink, K. D.. AU - Beitnere, U.. AU - OGeen, H.. AU - Anderson, A. E.. AU - Dindot, S. V.. AU - Nash, K. R.. AU - Weeber, E. J.. AU - Wöhr, M.. AU - Ellegood, J.. AU - Segal, D. J.. AU - Silverman, J. L.. PY - 2020/1/27. Y1 - 2020/1/27. N2 - Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, ...

Has E2-dependent E3 ubiquitin-protein ligase activity. May function together with E2 ubiquitin-conjugating enzymes UBE2D1/UBCH5A and UBE2D2/UBC4. Mediates ubiquitination of PXN/paxillin and Salmonella type III secreted protein sopA. May be involved in regulation of cell motility and localization of PXN/paxillin. Mediates the Lys-63-linked polyubiquitination of JKAMP thereby regulating JKAMP function by decreasing its association with components of the proteasome and ERAD; the ubiquitination appears to involve E2 ubiquitin-conjugating enzyme UBE2N. Mediates the Lys-48-linked polyubiquitination of TMEM173 at Lys-150 leading to its proteasomal degradation; the ubiquitination occurs in mitochondria after viral transfection and regulates antiviral responses.

Autosomal recessive juvenile Parkinsonism (AR-JP) is caused by mutations in a number of PARK genes, in particular in the E3 ubiquitin ligase Parkin (PARK2), and in its upstream protein kinase PINK1 (PARK6). PINK1 phosphorylates ubiquitin and the Parkin ubiquitin-like domain on structurally protected Ser65 to trigger mitophagy. We here report a crystal structure of a nanobody-stabilised complex between Pediculus humanus corporis (Ph)PINK1 with ubiquitin in the C-terminally retracted (Ub-CR) conformation. The structure reveals many peculiarities of PINK1, including the architecture of the C-terminal region, and reveals how the PINK1 N-lobe binds ubiquitin via a unique insertion ...

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group

EN] Seed longevity is important to preserve crops and wild plants and it is limited by progressive cellular damage (aging) during storage. The induction of cellular stress defenses and the formation of the seed coat are crucial protecting events during seed development, a process mediated in Arabidopsis thaliana by the transcription factors LEC1, LEC2, FUS3 and the abscisic acid-activated ABI3. In order to identify novel determinants of seed longevity we have screened an activation-tagging mutant collection of Arabidopsis and isolated a dominant mutant with increased seed longevity under both natural and accelerated aging conditions. Molecular characterization indicates that the mutant phenotype is caused by over-expression of the At2g26130 gene encoding a RING-type zinc finger putative ubiquitin ligase. Loss of function of this gene in a T-DNA insertion mutant resulted in decreased seed longevity. We named this important gene for seed longevity RSL1 (from Ring finger of Seed Longevity1) and we ...

TY - JOUR. T1 - Hect E3 ubiquitin ligase Tom1 controls Dia2 degradation during the cell cycle. AU - Kim, Dong Hwan. AU - Koepp, Deanna M.. PY - 2012/11/1. Y1 - 2012/11/1. N2 - The ubiquitin proteasome system plays a pivotal role in controlling the cell cycle. The budding yeast F-box protein Dia2 is required for genomic stability and is targeted for ubiquitin-dependent degradation in a cell cycle-dependent manner, but the identity of the ubiquitination pathway is unknown. We demonstrate that the Hect domain E3 ubiquitin ligase Tom1 is required for Dia2 protein degradation. Deletion of DIA2 partially suppresses the temperature-sensitive phenotype of tom1 mutants. Tom1 is required for Dia2 ubiquitination and degradation during G1 and G2/M phases of the cell cycle, whereas the Dia2 protein is stabilized during S phase. We find that Tom1 binding to Dia2 is enhanced in G1 and reduced in S phase, suggesting a mechanism for this proteolytic switch. Tom1 recognizes specific, positively charged residues ...

Linear ubiquitin chains are important regulators of cellular signalling pathways that control innate immunity and inflammation through nuclear factor (NF)-κB activation and protection against tumour necrosis factor-α-induced apoptosis. They are synthesized by HOIP, which belongs to the RBR (RING-bet …

We have probed the interactions between HOIP and NEMO by solving a cocrystal structure of NZF1 of human HOIP and CoZi of mouse NEMO, while our mutational studies have been performed using mouse HOIP. However, the surface residues from HOIP that interact with NEMO are fully conserved in human and mouse species (Fig. 3J). Our mutational analyses based on the structure of the cocrystal show that direct recognition of NEMO by HOIP plays a major role in NF-κB activation following conjugation of linear chains to NEMO. Although the RING-IBR-RING region of HOIP is the catalytic center for linear polyubiquitination by LUBAC (7), recent results obtained using an in vitro ubiquitin assay have suggested that the RING2 domain of HOIL-1L plays a role in linear polyubiquitination of NEMO (38). However, given that the HOIP-SHARPIN complex effectively linearly polyubiquitinates NEMO in vitro and activates NF-κB in cells (12), any involvement of the RING2 domain of HOIL-1L in linear polyubiquitination of NEMO ...

The ubiquitin E1, E2, and E3 ligase enzymes are the enzymatic core of the ubiquitination pathway. The E2-E3 complex interacts with the substrate, catalyzing ubiquitin addition to the substrate. Thus, the expression, activity, localization, and selectivity of ubiquitin E2s and E3s are important parameters that can serve to regulate ubiquitination. The E2-E3 combination used in the ubiquitination reaction can also influence the fate of the substrate through determining the extent and nature of ubiquitin addition. The majority of substrates observed to date are modified by the attachment of a Lys-48-linked ubiquitin chain, which targets the substrate for degradation by the 26S proteasome. Substrates modified with other types of polyubiquitin chains linked via ubiquitin Lys-6, -11, -29, and -63, or modified with a single ubiquitin, face different or unknown fates. For example, the heterodimeric E2 UBC13/methyl methane sulfonate sensitivity 2 functions with the RING E3 TNF receptor-associated factor ...

Protein neddylation is essential for the viability of most organisms and is widely involved in the regulation of immunity, DNA damage and repair, cell signaling and cell cycle. Unlike RING-type neddylation ligases, HECT-type neddylation ligase remains less defined. Here, we show that Itch is a novel HECT-type neddylation E3 ligase and we identify JunB as a substrate of Nedd8 modification by Itch. JunB neddylation attenuates its transcriptional activity. In addition, JunB neddylation mediated by Itch promotes its ubiquitination-dependent degradation. Therefore, these findings define a new HECT-type neddylation ligase and its neddylation substrate.

E3 ubiquitin ligases catalyze ubiquitination, which can target specific proteins for degradation. Although a growing number of E3 ubiquitin ligases and their targets have been identified, much less is known about the mechanisms that regulate their activity. A convergence of data indicate that phosphorylation regulates the binding of Nedd4-2, a HECT (homologous to the E6-AP C terminus) domain E3 ubiquitin ligase, to its target, the epithelial Na+ channel ENaC. Nedd4-2 phosphorylation is emerging as a central convergence point for the regulation of epithelial Na+ transport.. ...

The gene encoding deleted in breast cancer 2′ ((Rho-related BTB domain-containing protein 2), is classified being a tumor suppressor gene. for everyone natural procedures almost, including Nelfinavir Mesylate supplier cell development, apoptosis and differentiation.1 Dysregulation of the phenomenon qualified prospects to irreversible shifts in protein stability and will directly or indirectly promote a number of pathological conditions, including tumor.1 The procedure of ubiquitination involves multiple guidelines mediated by E1 ubiquitin-activating enzymes, E2 ubiquitin-conjugating enzymes and substrate-specific E3 ubiquitin ligases.2 One of the most predominant course of E3 ligases may be the category of really interesting brand-new gene (Band)-finger domain-containing protein. These protein are subdivided into two groupings: the monomeric RING-type E3 ligases as well as the multimeric RING-type E3 ligases, like the Cullin-3 (CUL3)-structured E3 ligases.2 The substrate specificity of CUL E3 ...

TY - JOUR. T1 - Effects of the combination of a proteasome inhibitor (PSI) and an inhibitor of ubiquitin-ligases (Leu-Ala) on the ultrastructure of human leukemic U937 cells. AU - Biały, P.. AU - Ziemba, H.. AU - Pleban, E.. AU - Wójcik, Cezary. PY - 2002/1/1. Y1 - 2002/1/1. N2 - We have used the dipeptide Leu-Ala in an attempt to prevent the formation of ubiquitin-protein conjugates in U937 cells by inhibition of cellular E3 enzymes (ubiquitin ligases). Proteasome inhibitors induce the formation of perinuclear aggregates for ubiquitinated proteins and proteasomes (aggresomes) in the area of the proteolytic center of the cell. Leu-Ala did not prevent the formation of those aggregates under the action of PSI (peptidyl aldehyde, selective inhibitor of the chymotrypsin-like activity of the proteasome), however it induced an accumulation of lipid droplets in treated cells, suggesting a previously unknown involvement of Leu-Ala in lipid metabolism. We conclude, that either Leu-Ala is not able to ...

A second member of the E3 ubiquitin ligases, Fbxo7, is also mutated in early-onset Parkisonism [91-97]. In contrast with Parkin, which functions as a single-polypeptide E3 ligase, Fbxo7 is a component of a multisubunit E3 ligase of the Cullin-RING ligase family (CRL). CRLs are a large class of multisubunit E3 ubiquitin ligases that feature a scaffolding protein, termed a cullin, and associate with a RING-box protein (reviewed in refs [98,99]). The archetypal CRL is the SCF-type ligase family, which comprises Cullin1, Skp1, the RING protein Rbx1, and an F-box. Skp1 associates with substrate adaptor proteins that contain F-boxes (Skp1-Cullin1-Fbox), which recruits substrates to the CRL for ubiquitylation.. Until recently, Fbxo7 had only four identified substrates. The first of these is HURP (hepatoma up-regulated protein) [100]. HURP is found at high levels in hepatocellular carcinomas and is required during mitotic spindle assembly for correct alignment of chromosomes [101]. As such, it is ...

During ubiquitination, Ub is initially activated by an ATP‐dependent E1 enzyme before it is passed to one of several distinct Ub‐conjugating enzymes (E2s). The E2 subsequently acts to either transfer Ub to a HECT (homologous to the E6AP carboxyl terminus)‐type Ub ligase (E3), or to catalyse substrate ubiquitination in conjunction with RING (really interesting new gene)‐type or U‐box E3 enzymes. An exception to this is the process of coupled monoubiquitination, through which E2 enzymes can catalyse the ubiquitination of Ub‐binding domain (UBD)‐containing proteins independently of E3 (Hoeller et al, 2006, 2007).. Ubiquitin ligases seem to be the crucial determinants of substrate selection and are also considered to be important components in controlling Ub‐chain formation on a substrate. For example, different HECT‐type E3s can specify both the linkage of a Ub chain and the process of its assembly. E6AP can form a Lys 48‐linked chain on its active cysteine residue (Scheffner & ...

A multiethnic series of patients with early-onset Parkinsons disease (EOP) was studied to assess the frequency and nature of parkin/PARK2 gene mutations and to investigate phenotype-genotype relationships. Forty-six EOP probands with an onset age of | 45 years, and 14 affected relatives were ascertained from Italy, Brazil, Cuba, and Turkey. The genetic screening included direct sequencing and exon dosage using a new, cost-effective, real-time polymerase chain reaction method. Mutations were found in 33% of the indexes overall, and in 53% of those with family history compatible with autosomal recessive inheritance. Fifteen parkin alterations (10 exon deletions and five point mutations) were identified, including four novel mutations: Arg402Cys, Cys418Arg, IVS11-3C | G, and exon 8-9-10 deletion. Homozygous mutations, two heterozygous mutations, and a single heterozygous mutation were found in 8, 6, and 1 patient, respectively. Heterozygous exon deletions represented 28% of the mutant alleles. The

TY - JOUR. T1 - Vps9p CUE domain ubiquitin binding is required for efficient endocytic protein traffic. AU - Davies, Brian A.. AU - Topp, Justin D.. AU - Sfeir, Agnel J.. AU - Katzmann, David J.. AU - Carney, Darren S.. AU - Tall, Gregory G.. AU - Friedberg, Andrew S.. AU - Deng, Li. AU - Chen, Zhijian. AU - Horazdovsky, Bruce F.. PY - 2003/5/30. Y1 - 2003/5/30. N2 - Rab5 GTPases are key regulators of protein trafficking through the early stages of the endocytic pathway. The yeast Rab5 ortholog Vps21p is activated by its guanine nucleotide exchange factor Vps9p. Here we show that Vps9p binds ubiquitin and that the CUE domain is necessary and sufficient for this interaction. Vps9p ubiquitin binding is required for efficient endocytosis of Ste3p but not for the delivery of the biosynthetic cargo carboxypeptidase Y to the vacuole. In addition, Vps9p is itself monoubiquitylated. Ubiquitylation is dependent on a functional CUE domain and Rsp5p, an E3 ligase that participates in cell surface receptor ...

MKRN2 is a novel ubiquitin E3 ligase for the p65 subunit of NF-κB and negatively regulates inflammatory responses.MKRN2 is a novel ubiquitin E3 ligase for the p65 subunit of NF-κB and negatively regulates inflammatory responses. ...

Misfolded proteins of the endoplasmic reticulum (ER) are targeted to the cytoplasm for proteasomal degradation. Key components of this process are ER membrane-bound ubiquitin ligases. These ligases associate with the cytoplasmic AAA-ATPase Cdc48p/p97, which is thought to support the release of malfolded proteins from the ER. Here, we characterize a yeast protein complex containing the ubiquitin ligase Hrd1p and the ER membrane proteins Hrd3p and Der1p. Hrd3p binds malfolded proteins in the ER lumen enabling their delivery to downstream components. Therefore, we propose that Hrd3p acts as a substrate recruitment factor for the Hrd1p ligase complex. Hrd3p function is also required for the association of Cdc48p with Hrd1p. Moreover, our data demonstrate that recruitment of Cdc48p depends on substrate processing by the Hrd1p ligase complex. Thus, the Hrd1p ligase complex unites substrate selection in the ER lumen and polyubiquitination in the cytoplasm and links these processes to the release of ER ...

Background RBR ubiquitin ligases are components of the ubiquitin-proteasome system present in all eukaryotes. They are characterized by having the RBR (RING - IBR - RING) supradomain. In this study, the patterns of emergence of RBR genes in plants are described. Methodology/Principal Findings Phylogenetic and structural data confirm that just four RBR subfamilies (Ariadne, ARA54, Plant I/Helicase and Plant II) exist in viridiplantae. All of them originated before the split that separated green algae from the rest of plants. Multiple genes of two of these subfamilies (Ariadne and Plant II) appeared in early plant evolution. It is deduced that the common ancestor of all plants contained at least five RBR genes and the available data suggest that this number has been increasing slowly along streptophyta evolution, although losses, especially of Helicase RBR genes, have also occurred in several lineages. Some higher plants (e. g. Arabidopsis thaliana, Oryza sativa) contain a very large number of RBR genes

Project title: Regulation and control of linear ubiquitin chian synthesis: Structure, function and mechanism of linear ubiquitin chian assembly complex LUBAC. Summary: The linear ubiquitin chain assembly complex LUBAC is E3 ubiquitin ligase that plays pivotal roles in the innitiation of innate and adpative immune response, especially in the activation of nuclear factor-kappa B, which is a transcription factor that induces transcription of inflammatory genes. Abberrant LUBAC activity has been known as a contributor to diffuse large B-cell lymphoma (DLBL), which is a bone marrow malignancy. More importantly, individuals carrying congenital mutaions in LUBAC protein domains (i.e. HOIP, HOIL-1, SHARPIN) manifest devastating immunodeficiency and/or autoinflammatory symptoms. All those add up to the fact that LUBAC is really interesting and important. This project aims to unveal regulatory mechanisms for LUBAC activity with aid from biochemical and structural biology techiniques (i.e. in vitro protein ...

We report the map-based cloning of the SLY1 gene of Arabidopsis. SLY1 is a positive regulator of GA response. Recessive mutations in SLY1 affect the full range of GA phenotypes, including feedback regulation of the GA3ox1 biosynthetic gene (Figure 1). Thus, the fact that SLY1 encodes a putative F-box protein suggests that the GA signal is transmitted via an SCFSLY1 E3 ubiquitin ligase.. Ubiquitylation controls target protein activity at multiple levels, including proteolysis and the potentiation of transcriptional activation domains (Conaway et al., 2002). Major members of the SCF complex include homologs of SKP1, cullin, and the RING-finger domain protein Rbx1 (Zheng et al., 2002). The F-box subunit directs the interaction of the complex with a specific target for ubiquitylation. The conserved F-box domain allows the protein to interact with the SKP1 subunit of the SCF. SKP1 tethers the F-box protein to the N terminus of cullin. The RING-finger protein Rbx1 binds the C terminus of cullin and ...

Evidence suggests that regulated ubiquitination of proteins plays a critical role in the development and plasticity of the central nervous system. We have previously identified the ubiquitin ligase Praja1 as a gene product induced during fear memory consolidation. However, the neuronal function of this enzyme still needs to be clarified. Here, we investigate its involvement in the nerve growth factor (NGF)-induced differentiation of rat pheochromocytoma (PC12) cells. Praja1 co-localizes with cytoskeleton components and the neurotrophin receptor interacting MAGE homologue (NRAGE). We observed an enhanced expression of Praja1 after 3 days of NGF treatment and a suppression of neurite formation upon Praja1 overexpression in stably transfected PC12 cell lines, which was associated with a proteasome-dependent reduction of NRAGE levels. Our data suggest that Praja1, through ubiquitination and degradation of NRAGE, inhibits neuronal differentiation. The two murine isoforms, Praja1.1 and Praja1.2, appear to be

TY - JOUR. T1 - The E3 ligase Aip4/Itch ubiquitinates and targets ErbB-4 for degradation. AU - Omerovic, Jasminka. AU - Santangelo, Laura. AU - Puggioni, Eleonora Maria Rosaria. AU - Marrocco, Jordan. AU - DallArmi, Claudia. AU - Palumbo, Camilla. AU - Belleudi, Francesca. AU - Di Marcotullio, Lucia. AU - Frati, Luigi. AU - Torrisi, Maria Rosaria. AU - Cesareni, Gianni. AU - Gulino, Alberto. AU - Alimandi, Maurizio. PY - 2007/9. Y1 - 2007/9. N2 - The ErbB-4 receptors are unique in the EGFR/ErbB family for the ability to associate with WW domain-containing proteins. To identify new ligands of the cytoplasmic tail of ErbB-4, we panned a brain cDNA phage library with ErbB-4 peptides containing sequence motifs corresponding to putative docking sites for class-I WW domains. This approach led to identification of AIP4/Itch, a member of the Nedd4-like family of E3 ubiquitin protein ligases, as a protein that specifically interacts with and ubiquitinates ErbB-4 in vivo. Interaction with the ErbB-4 ...

HPK1, a member of mammalian Ste20-like serine/threonine kinases, is lost in |95% pancreatic cancer through proteasome-mediated degradation. However, the mechanism of HPK1 loss has not been defined. The aims of this study are to identify the ubiquitin ligase and to examine the mechanisms that targets HPK1 degradation. We found that the CUL7/Fbxw8 ubiquitin ligase targeted HPK1 for degradation via the 26 S proteasome. The ubiquitination of HPK1 required its kinase activity and autophosphorylation. Wild-type protein phosphatase 4 (PP4), but not the phosphatase-dead PP4 mutant, PP4-RL, inhibits the interaction of Fbxw8 with HPK1 and Fbxw8-mediated ubiquitination of HPK1. In addition, we showed that Thr-355 of HPK1 is a key PP4 dephosphorylation site, through which CUL7/Fbxw8 ubiquitin ligase and PP4 regulates HPK1 stability. Knockdown of Fbxw8 restores endogenous HPK1 protein expression and inhibits cell proliferation of pancreatic cancer cells. Our study demonstrated that targeted degradation of HPK1 by

Polycomb group proteins Bmi-1 and Ring1B are core subunits of the PRC1 complex, which plays important roles in the regulation of Hox gene expression, X-chromosome inactivation, tumorigenesis, and stem cell self-renewal. The RING finger protein Ring1B is an E3 ligase that participates in the ubiquitination of lysine 119 of histone H2A, and the binding of Bmi-1 stimulates the E3 ligase activity. We have mapped the regions of Bmi-1 and Ring1B required for efficient ubiquitin transfer and determined a 2.5-A structure of the Bmi-1-Ring1B core domain complex. The structure reveals that Ring1B hugs Bmi-1 through extensive RING domain contacts and its N-terminal tail wraps around Bmi-1. The two regions of interaction have a synergistic effect on the E3 ligase activity. Our analyses suggest a model where the Bmi-1-Ring1B complex stabilizes the interaction between the E2 enzyme and the nucleosomal substrate to allow efficient ubiquitin transfer.. ...

The herpes simplex virus type 1 (HSV-1) encoded E3 ubiquitin ligase, infected cell protein 0 (ICP0), is required for efficient lytic viral replication and regulates the switch between the lytic and latent states of HSV-1. As an E3 ubiquitin ligase, ICP0 directs the proteasomal degradation of several cellular targets, allowing the virus to counteract different cellular intrinsic and innate immune responses. In this review, we will focus on how ICP0s E3 ubiquitin ligase activity inactivates the host intrinsic defenses, such as nuclear domain 10 (ND10), SUMO, and the DNA damage response to HSV-1 infection. In addition, we will examine ICP0s capacity to impair the activation of interferon (innate) regulatory mediators that include IFI16 (IFN γ-inducible protein 16), MyD88 (myeloid differentiation factor 88), and Mal (MyD88 adaptor-like protein). We will also consider how ICP0 allows HSV-1 to evade activation of the NF-κB (nuclear factor kappa B) inflammatory signaling pathway. Finally, ICP0s ...

TY - JOUR. T1 - Ubiquitin ligases. T2 - Cell-cycle control and cancer. AU - Nakayama, Keiichi I.. AU - Nakayama, Keiko. PY - 2006/5/1. Y1 - 2006/5/1. N2 - A driving force of the cell cycle is the activation of cyclin-dependent kinases (CDKs), the activities of which are controlled by the ubiquitin-mediated proteolysis of key regulators such as cyclins and CDK inhibitors. Two ubiquitin ligases, the SKP1-CUL1-F-box-protein (SCF) complex and the anaphase-promoting complex/cyclosome (APC/C), are responsible for the specific ubiquitylation of many of these regulators. Deregulation of the proteolytic system might result in uncontrolled proliferation, genomic instability and cancer. Cumulative clinical evidence shows alterations in the ubiquitylation of cell-cycle regulators in the aetiology of many human malignancies. A better understanding of the ubiquitylation machinery will provide new insights into the regulatory biology of cell-cycle transitions and the development of anti-cancer drugs.. AB - A ...

MalaCards based summary : Itch E3 Ubiquitin Ligase Deficiency, also known as autoimmune disease, syndromic multisystem, is related to autoimmune disease, multisystem, with facial dysmorphism and autoimmune disease. An important gene associated with Itch E3 Ubiquitin Ligase Deficiency is ITCH (Itchy E3 Ubiquitin Protein Ligase). Affiliated tissues include liver and thyroid ...

A multitude of studies have demonstrated that the early phases of DNA replication are regulated by ubiquitylation. For instance, the E3 ubiquitin ligase complexes cullin-RING ligase-1 (CRL1) and cullin-RING ligase-4 (CRL4) prevent re-replication and the occurrence of genome instability by targeting pre-RC components for proteasomal degradation (reviewed in Truong et al.2). Cullin-RING ligases (CRLs) constitute a protein family of ,200 modular E3s and are composed of eight distinct subfamilies containing different cullins, namely CUL1, CUL2, CUL3, CUL4A, CUL4B, CUL5, CUL7 and CUL9.3 Cullins work as molecular scaffolds assembling the different complex subunits, that is, a RING-finger protein (RBX1 or RBX2), which interacts with the ubiquitin-conjugating enzyme, an adaptor protein and one of many substrate-receptor subunits. The activity of CRLs is primarily controlled at the level of substrate recruitment. The direct recognition of the target protein by the substrate-receptor subunit and its ...

Ubiquitin-binding protein that interacts with the BRCA1-BARD1 heterodimer, and regulates its activity. Specifically binds Lys-6-linked polyubiquitin chains. Interaction with autoubiquitinated BRCA1, leads to inhibit the E3 ubiquitin-protein ligase activity of the BRCA1-BARD1 heterodimer. Component of a complex required to couple deglycosylation and proteasome-mediated degradation of misfolded proteins in the endoplasmic reticulum that are retrotranslocated in the cytosol ...

PINK1 regulation of neuronal and mitochondrial homeostasis PROJECT SUMMARY. Mutations in PTEN-induced kinase 1 (PINK1) cause familial autosomal recessive parkinsonism. As PINK1 plays a neuroprotective role in a wide range of genetic and toxin-induced Parkinsons disease (PD) models, studying its function in neurons may offer particular insights into potential therapeutic strategies. In the prior project period, we found that endogenous PINK1 exists in mitochondrial and cytosolic compartments. Moreover, these pools of PINK1 played divergent roles in regulating mitochondrial fission-fusion, mitophagy, calcium homeostasis and dendritic morphogenesis. Using primary neurons, differentiated neuronal cell lines and Pink1 knockout and control mice, the current proposal focuses on studying mechanisms by which PINK1 regulates neuron differentiation and the maintenance of extended axo-dendritic arbors. Based on preliminary data, we hypothesize that PINK1 interacts with cytosolic targets to regulate neuron ...

Background: RING is one of the largest E3 ubiquitin ligase families and C3H2C3 type is the largest subfamily of RING, playing an important role in plants development and growth and their biotic and abiotic stress responses. Results: A total of 143 RING...

TY - JOUR. T1 - In vitro reconstitution defines the minimal requirements for Cdc48-dependent disassembly of the CMG helicase in budding yeast. AU - Mukherjee, Progya. AU - Labib, Karim. N1 - We gratefully acknowledge the support of the Medical Research Council (core grant MC_UU_12016/13 to KL) and the Wellcome Trust (reference 102943/Z/13/Z for an Investigator award to KL).. PY - 2019/9/10. Y1 - 2019/9/10. N2 - Disassembly of the replisome is the final step of chromosome duplication in eukaryotes. In budding yeast and metazoa, cullin ubiquitin ligases are required to ubiquitylate the Cdc45-MCM-GINS (CMG) helicase that lies at the heart of the replisome, leading to a disassembly reaction that is dependent upon the ATPase known as Cdc48 or p97. Here, we describe the reconstitution of replisome disassembly, using a purified complex of the budding yeast replisome in association with the cullin ligase SCF Dia2. Upon addition of E1 and E2 enzymes, together with ubiquitin and ATP, the CMG helicase is ...

The protein encoded by this gene is a member of the tripartite motif (TRIM) family. The TRIM motif includes three zinc-binding domains, a RING, a B-box type 1 and a B-box type 2, and a coiled-coil region. This protein is also a member of the ADP ribosylation factor family of guanine nucleotide-binding family of proteins. Its carboxy terminus contains an ADP-ribosylation factor domain and a guanine nucleotide binding site, while the amino terminus contains a GTPase activating protein domain which acts on the guanine nucleotide binding site. The protein localizes to lysosomes and the Golgi apparatus. It plays a role in the formation of intracellular transport vesicles, their movement from one compartment to another, and phopholipase D activation. Three alternatively spliced transcript variants for this gene have been described. [provided by RefSeq, Jul 2008 ...

Mcl-1 is an anti-apoptotic protein of the Bcl-2 family that is essential for the survival of multiple cell lineages and that is highly amplified in human cancer. Under physiological conditions, Mcl-1 expression is tightly regulated at multiple levels, involving transcriptional, post-transcriptional and post-translational processes. Ubiquitination of Mcl-1, that targets it for proteasomal degradation, allows for rapid elimination of the protein and triggering of cell death, in response to various cellular events. In the last decade, a number of studies have elucidated different pathways controlling Mcl-1 ubiquitination and degradation. Four different E3 ubiquitin-ligases (e.g., Mule, SCFβ-TrCP, SCFFbw7 and Trim17) and one deubiquitinase (e.g., USP9X), that respectively mediate and oppose Mcl-1 ubiquitination, have been formerly identified. The interaction between Mule and Mcl-1 can be modulated by other Bcl-2 family proteins, while recognition of Mcl-1 by the other E3 ubiquitin-ligases and

PTEN-induced putative kinase 1 (PINK1) is a mitochondrial serine/threonine-protein kinase encoded by the PINK1 gene. It is thought to protect cells from stress-induced mitochondrial dysfunction. PINK1 activity causes the parkin protein to bind to depolarized mitochondria to induce autophagy of those mitochondria. PINK1 is processed by healthy mitochondria and released to trigger neuron differentiation. Mutations in this gene cause one form of autosomal recessive early-onset Parkinsons disease. PINK1 is synthesized as a 63000 Da protein which is often cleaved by PARL, between the 103-Alanine and the 104-Phenylalanine residues, into a 53000 Da fragment. PINK1 contains an N-terminal mitochondrial localization sequence, a putative transmembrane sequence, a Ser/Thr kinase domain, and a C-terminal regulatory sequence. The protein has been found to localize to the outer membrane of mitochondria, but can also be found throughout the cytosol. Experiments suggest the Ser/Thr kinase domain faces outward ...

Background: Although neuronal extracellular sensing is emerging as crucial for brain wiring and therefore plasticity, little is known about these processes in neurodevelopmental disorders. Ubiquitin protein ligase E3A (UBE3A) plays a key role in neurodevelopment. Lack of UBE3A leads to Angelman syndrome (AS), while its increase is among the most prevalent genetic causes of autism (e.g., Dup15q syndrome). By using microstructured substrates that can induce specific directional stimuli in cells, we previously found deficient topographical contact guidance in AS neurons, which was linked to a dysregulated activation of the focal adhesion pathway. Methods: Here, we study axon and dendrite contact guidance and neuronal morphological features of wild-type, AS, and UBE3A-overexpressing neurons (Dup15q autism model) on micrograting substrates, with the aim to clarify the role of UBE3A in neuronal guidance. Results: We found that loss of axonal contact guidance is specific for AS neurons while UBE3A ...

TY - JOUR. T1 - The isolated N terminus of Ring1B is a well-folded, monomeric fragment with native-like structure. AU - Martínez-Gómez, Ana Isabel. AU - Villegas, Sandra. AU - Aguado-Llera, David. AU - Bacarizo, Julio. AU - Cámara-Artigas, Ana. AU - Vidal, Miguel. AU - Neira, José L.. PY - 2014/1/1. Y1 - 2014/1/1. N2 - The Polycomb group (PcG) proteins assemble into Polycomb repressive complexes (PRCs), PRC1 and PRC2, which act as general transcriptional repressors. PRC1 comprises a variety of biochemical entities endowed with histone H2A monoubiquitylation activity conferred by really interesting new gene (RING) finger E3 ubiquitin ligases Ring1A and Ring1B. All PRC1 complexes contain Ring1 proteins which are essential for Polycomb epigenetic regulation. We have been able to express the isolated N-terminal region of Ring1B, N-Ring1B, comprising the first 221 residues of the 334-residue-long Ring1B. This fragment contains the 41-residue-long RING finger motif, and flanking sequences that ...

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Ubiquitin regulation appears to have an important but not well-understood role in C. elegans embryonic polarization. One of the earliest discoveries was that PAR-2 has homology to RING domain E3 ubiquitin ligases, suggesting that ubiquitin ligase activity may be important for excluding anterior PARs from the posterior [5], [37]. Hao and colleagues showed that the PAR-2 RING domain is required for robust transgene rescue of embryos lacking endogenous PAR-2, indicating that it is likely to be an active ubiquitin ligase in vivo, although this activity is not absolutely essential for function [25]. Biochemical targets of PAR-2, however, are unknown. Other results that relate ubiquitin-based regulation to polarization include the finding that PAR-6 levels are affected by activity of the ubiquitin ligase CUL-2 and its adapter protein FEM-3 [44], and that mutations of C. elegans homologs of the BRAT family of ubiquitin ligases have been shown to be able to suppress weak par-2 phenotypes [45]. Weak ...

Recently, it has become known that current treatments of advanced PCa, based on androgen ablation therapies such as surgical and chemical castration, are very effective treatments initially, but almost all cases progress to CRPC eventually. Accumulating evidence has revealed that in nearly all cases resumption of AR transcription activity contributes to CRPC progression [25]. A recently identified mechanism, in which E3 ubiquitin ligase Siah2 regulates a subset of AR bound to corepressor NCoR1, results in removal of transcriptionally-inactive AR from chromatin and allows p300-bound AR binding to AREs, the mechanism of which has become the center of attention in PCa treatment investigations [14].. Interestingly, NO inhibition of AR-function in PCa cells was first described in vitro using the NO-donor DETA/NO. This study showed that NO inhibited AR-mediated genomic function by preventing its DNA-binding activity while not decreasing AR protein concentrations or decreasing nuclear AR translocation ...

Mitochondria of adult cardiac myocytes are seemingly static, without apparent organelle fission and fusion. Nevertheless, interruption of mitochondrial fusion or fission pathways in cardiac myocytes provokes lethal cardiomyopathies.1 To resolve this paradox, we proposed functioning of mitochondrial fusion and fission factors in mitophagy.2 Thus, mitofusin 2 comediates mitochondrial fusion with mitofusin 1,3 but is also a mitochondrial receptor for the mitophagy effector, Parkin.4,5 A role for mitochondrial fission in mitophagy is less well defined. Three independent reports of cardiac myocyte-specific ablation of profission dynamin-related protein 1 (Drp1) described cardiomyopathy and abnormal mitophagy,6-8 but the underlying mechanisms are controversial; mitophagy was variously described as decreased,7 increased,8 or initiated independent of Parkin, but interrupted.6 Conclusions about Parkin-mediated mitophagy in the heart are uncertain because the germ-line Parkin knockout mouse has no ...

The covalent attachment of ubiquitin to substrate proteins (ubiquitylation) is a post-translational modification that has major roles in regulating protein turnover and cell signalling. An E1-E2-E3 enzyme cascade tightly controls this process, but the nature of ubiquitin modification is highly variable. Single ubiquitin moieties or polyubiquitin chains of eight different linkages can be attached to proteins. The E2 ubiquitin conjugating enzymes and E3 ubiquitin ligases have critical roles in determining both the substrate and the type of ubiquitin modification. A large family of E3 ubiquitin ligases that contain both substrate recruitment and RING domains confer specificity within the ubiquitylation cascade. To activate ubiquitin transfer, RING domains bind an E2~ubiquitin conjugate and stabilise the ubiquitin moiety in a defined conformation that primes the active site on the E2 for nucleophilic attack. However, from the few examples that have been characterised, it is already clear that ...

Parkinsons disease (PD) is characterized by a progressive loss of midbrain dopamine neurons and the presence of cytoplasmic inclusions called Lewy bodies. Mutations in several genes including alpha-synuclein and parkin have been linked to familial PD. The loss of parkins E3-ligase activity leads to dopaminergic neuronal degeneration in early-onset autosomal recessive juvenile parkinsonism, suggesting a key role of parkin for dopamine neuron survival. To evaluate the potential neuroprotective role of parkin in the pathogenesis of PD, we tested whether overexpression of wild-type rat parkin could protect against the toxicity of mutated human A30P alpha-synuclein in a rat lentiviral model of PD. Animals overexpressing parkin showed significant reductions in alpha-synuclein-induced neuropathology, including preservation of tyrosine hydroxylase-positive cell bodies in the substantia nigra and sparing of tyrosine hydroxylase-positive nerve terminals in the striatum. The parkin-mediated neuroprotection was

Autor: Pizon, Véronique et al.; Genre: Zeitschriftenartikel; Im Druck veröffentlicht: 2002; Keywords: myosin; microtubules; titin; MURF2; myofibril; assembly; connectin; Titel: Transient association of titin and myosin with microtubules in nascent myofibrils directed by the MURF2 RING-finger protein

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Dysfunctional mitochondria cause many neurodegenerative disorders and with aging in general, mechanisms of mitochondrial quality control are essential for cellular function. Keeping mitochondria in a healthy state is a complex process, which is tightly regulated by several mitochondrial quality control systems. An ubiquitin-mediated proteasome-dependent protein degradation pathway, termed outer mitochondrial-associated degradation (OMMAD), was recently described. OMMAD provides mitochondrial protein quality control to prevent mitochondrial damage. Up until now, four outer mitochondrial membrane-anchored RING finger ubiquitin ligases as well as the AAA-ATPase p97 were described as OMMAD components. Here, we further characterize the mitochondrial RING finger protein MARCH9. We found that MARCH9 is an unstable protein degraded in a proteasomal-dependent manner. Furthermore MARCH9 interacts physically with both mitofusins, Mfn1 and Mfn2, both involved in the mitochondrial fusion. The ...

Eukaryotes contain a highly conserved multienzyme system which covalently links a small protein, ubiquitin, to a variety of intracellular proteins that bear degradation signals recognized by this system. The resulting ubiquitin-protein conjugates are degraded by the 26S proteasome, an ATP-dependent protease. Pathways that involve ubiquitin play major roles in a huge variety of processes, including cell differentiation, cell cycle, and responses to stress. In this article we briefly review the design of the ubiquitin system, and describe two recent advances, the finding that ubiquitin ligases interact with specific components of the 26S proteasome, and the demonstration that peptides accelerate their uptake into cells by activating the N-end rule pathway, one of several proteolytic pathways of the ubiquitin system.. ...

Ubiquitin received its name because of its ubiquitous expression in eukaryotic cells. Since its discovery more than 40 years ago, the covalent attachment of ubiquitin to proteins has become well established as a degradative signal. However, more recently it has become clear that protein degradation is only one of many processes regulated by ubiquitylation and it has emerged that this 76 amino acid protein is also crucial for the regulation of numerous cellular processes. For example, ubiquitin is also involved in endocytosis, membrane trafficking, DNA repair, and the regulation of signalling pathways and the cell cycle. In this issue, we conclude our Ubiquitin Minifocus with three articles that provide further insight into the diverse roles of ubiquitylation. E3 ubiquitin ligases are central to the post-translational modification of proteins with ubiquitin and - in a Cell Science at a Glance article (p. 531) - Meredith Metzger, Ventzislava Hristova and Allan Weissman provide an overview of the ...

Cullin-RING E3 ligases (CRLs) are the largest known family of ubiquitin ligases. The activity of some CRLs is inhibited by an eight-subunit complex known as the COP9 signalosome, which can act on the cullin subunit of CRLs and thereby influence the ubiquitylation of CRL substrates. On p. 1035, Lionel Pintard and colleagues use mass spectrometry to identify the subset of CRLs that might be regulated by the COP9 signalosome. By determining the adaptor proteins with which six of the COP9-signalosome subunits interact, the authors identify 15 CRLs that associate with the COP9 signalosome. Interestingly, most of these CRLs have a role in DNA metabolism; the authors propose that their coordinated regulation might ensure rapid CRL-mediated responses to specific physiological cues. The authors mass spectrometry analysis also reveals that Dda1, a small protein that is thought to associate with CRL4 complexes, positively regulates their ubiquitin-ligase activity. Interestingly, the expression of Dda1 and ...

Cullin-RING E3 ubiquitin ligase complexes play a central role in targeting cellular proteins for ubiquitination-dependent protein turnover through 26S proteasome. Cullin-2 is a member of the Cullin family, and it serves as a scaffold protein for Elongin B and C, Rbx1 and various substrate recognition receptors to form E3 ubiquitin ligases. First, the composition, structure and the regulation of Cullin-2 based E3 ubiquitin ligases were introduced. Then the targets, the biological functions of complexes that use VHL, Lrr-1, Fem1b, Prame, Zyg-11, BAF250, Rack1 as substrate targeting subunits were described, and their involvement in diseases was discussed. A small molecule inhibitor of Cullins as a potential anti-cancer drug was introduced. Furthermore, proteins with VHL box that might bind to Cullin-2 were described. Finally, how different viral proteins form E3 ubiquitin ligase complexes with Cullin-2 to counter host viral defense were explained. Cullin-2 based E3 ubiquitin ligases, using many different

|jats:p|Ubiquitin is a versatile post-translational modification which is covalently attached to protein targets either as a single moiety or as a ubiquitin chain. In contrast to K48 and K63-linked chains which have been extensively studied, the regulation and function of most atypical ubiquitin chains is only starting to emerge. The deubiquitinase TRABID/ZRANB1 is tuned for the recognition and cleavage of K29 and K33-linked chains. Yet, substrates of TRABID and the cellular functions of these atypical ubiquitin signals remain unclear. We determined the interactome of two TRABID constructs rendered catalytic dead either through a point mutation in the catalytic cysteine residue or through removal of the OTU catalytic domain. We identified 50 proteins trapped by both constructs and which therefore represent candidate substrates of TRABID. We then validated the E3 ubiquitin ligase HECTD1 as a substrate of TRABID and used UbiCREST and Ub-AQUA proteomics to show that HECTD1 preferentially assembles K29- and

Uniprot: Necessary for the fragmentation of Golgi stacks during mitosis and for their reassembly after mitosis. Involved in the formation of the transitional endoplasmic reticulum (tER). The transfer of membranes from the endoplasmic reticulum to the Golgi apparatus occurs via 50-70 nm transition vesicles which derive from part-rough, part-smooth transitional elements of the endoplasmic reticulum (tER). Vesicle budding from the tER is an ATP-dependent process. The ternary complex containing UFD1, VCP and NPLOC4 binds ubiquitinated proteins and is necessary for the export of misfolded proteins from the ER to the cytoplasm, where they are degraded by the proteasome. The NPLOC4-UFD1-VCP complex regulates spindle disassembly at the end of mitosis and is necessary for the formation of a closed nuclear envelope. Regulates E3 ubiquitin-protein ligase activity of RNF19A. Component of the VCP/p97-AMFR/gp78 complex that participates in the final step of the sterol-mediated ubiquitination and endoplasmic ...

New Investigator Award: $90,000 over two years. Scientific title: Critical role of Parkin as an anti-oxidant in mitochondria; new concept of Parkin function Although the parkin gene has been identified as critical to the development of early-onset Parkinsons disease, researchers still do not know exactly what role it plays within cells and in cell death. At the University of Ottawa, Dr. Tohru Kitada, a neurologist, is investigating the way parkin interacts with mitochondria, the parts of cells that generate energy and oxidative stress.. Kitada was a leading researcher on the original team in Japan that identified the parkin gene. Now, hes using embryonic fibroblasts from mice to try to pinpoint the role of missing parkin in forcing mitochondria to generate oxidative stress, the process within cells that produces reactive oxygen molecules and can damage brain cells ...

UBE2J1 Full-Length MS Protein Standard (NP_057105), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. The modification of proteins with ubiquitin is an important cellular mechanism for targeting abnormal or short-lived proteins for degradation. Ubiquitination involves at least three classes of enzymes: ubiquitin-activating enzymes, or E1s, ubiquitin-conjugating enzymes, or E2s, and ubiquitin-protein ligases, or E3s. This gene encodes a member of the E2 ubiquitin-conjugating enzyme family. This enzyme is located in the membrane of the endoplasmic reticulum (ER) and may contribute to quality control ER-associated degradation by the ubiquitin-proteasome system.

The SCOP classification for the Adenylation domain of NAD+-dependent DNA ligase family. Additional information, provided for both this family and the superfamily it belongs to, includes SUPERFAMILY links to genome assignments, alignments, domain combinations, taxonomic visualisation and hidden Markov model information.

Cohesion between sister chromatids is established during DNA replication and depends on a protein complex called cohesin. At the metaphase-anaphase transition in the yeast Saccharomyces cerevisiae, the ESP1-encoded protease separin cleaves SCC1, a subunit of cohesin with a relative molecular mass of 63,000 (Mr 63K). The resulting 33K carboxy-terminal fragment of SCC1 bears an amino-terminal arginine-a destabilizing residue in the N-end rule. Here we show that the SCC1 fragment is short-lived (t1/2 approximately 2 min), being degraded by the ubiquitin/proteasome-dependent N-end rule pathway. Overexpression of a long-lived derivative of the SCC1 fragment is lethal. In ubr1Delta cells, which lack the N-end rule pathway, we found a highly increased frequency of chromosome loss. The bulk of increased chromosome loss in ubr1Delta cells is caused by metabolic stabilization of the ESP1-produced SCC1 fragment. This fragment is the first physiological substrate of the N-end rule pathway that is targeted through

Upon recruitment to the viral promoter, P-TEFb and ELL2 act on the same polymerase enzyme to synergistically activate HIV transcription. The sequestration into a SEC and interaction with Tat also stabilize ELL2, which otherwise would be a short-lived protein targeted by the E3 ubiquitin ligase Siah1 for proteasomal degradation. Besides being recruited by Tat/TAR to activate HIV, SEC is also employed by the mixed-lineage leukemia (MLL) protein and its fusion partners to promote the expression of MLL-target genes and leukemogenesis. In addition to SEC, our data indicate that P-TEFb also exists in at least two other complexes (Fig. 1). First, most cellular P-TEFb is normally sequestered in an inactive state in the 7SK snRNP. We have previously identified 7SK snRNA as well as HEXIM1/2, LARP7 and MePCE proteins as key subunits of this complex and determined their roles in inhibiting CDK9 kinase, maintaining 7SK snRNP integrity and suppressing cellular transformation. A number of conditions/reagents ...

In the ubiquitin-mediated pathway for the degradation of intracellular proteins, several molecules of ubiquitin are linked to the protein substrate by amide linkages. It was noted that the number of ubiquitin-protein conjugates and their apparent molecular size are higher than expected from the number of amino groups in the protein. When the amino groups of ubiquitin were blocked by reductive methylation, it was efficiently conjugated to lysozyme, but the higher-molecular-weight conjugates were not formed. This suggests that the higher-molecular-weight conjugates with native ubiquitin contain structures in which one molecule of ubiquitin is linked to an amino group of another molecule of ubiquitin. Methylated ubiquitin stimulated protein breakdown at about one half the rate obtained with native ubiquitin, and isolated conjugates of 125I-lysozyme with methylated ubiquitin were broken down by reticulocyte extracts. These findings indicate that the formation of polyubiquitin chains is not ...

The identification of hundreds of somatic mutations in cancer genomes has raised critical questions as to their functional relevance. Despite efforts to analyse such mutations computationally, our work demonstrates the importance of direct functional testing, in particular of large genes mutated at moderate levels. Our work shows, by robust genetic characterisation, that Huwe1 is a tumour suppressor in the small intestine and colon. Together with our identification of HUWE1 mutations present in human CRC that perturb its ubiquitin ligase activity, this strongly suggests it is a bona fide colonic tumour suppressor gene.. This is particularly important as previous work on HUWE1s tumourigenic role had proven controversial. HUWE1 is an E3 ubiquitin ligase that controls the stability of MCL1, MYC and MYCN functions which would suggest a tumour‐suppressive role. Indeed, work using chemically induced skin cancer mouse models has indicated this is the case (Inoue et al, 2013). However, via ...

Predicted to have ubiquitin conjugating enzyme binding activity and ubiquitin protein ligase activity. Predicted to be involved in positive regulation of proteasomal ubiquitin-dependent protein catabolic process; protein polyubiquitination; and ubiquitin-dependent protein catabolic process. Predicted to localize to mitochondrial membrane and ubiquitin ligase complex. Orthologous to human RNF144B (ring finger protein 144B ...

Phytohormone abscisic acid (ABA) regulates key processes in plants relative to seed germination, plant development and responses to important environmental stresses, such as drought, salinity and extreme temperatures. ABA perception is tightly controlled by the ubiquitin proteasome system. CRL4-CDDD E3 ubiquitin ligases target ABA receptors of the PYR/PYL/RCAR (pyrabactin resistance/pyrabactin resistance-like/regulatory components of ABA) family, triggering their ubiquitination and proteasomal degradation. Therefore, CRL4-CDDD complexes function as repressors of ABA-mediated stress responses. On the contrary, ABA treatment attenuates receptor degradation although the precise molecular details of this mechanism have remained unknown. In this seminar, our most recent data on the regulatory process underlying ABA-mediated protection of PYR/PYL/RCAR receptors, by CRL4-CDDD E3 ubiquitin ligases inactivation, will be shown.. ...

TY - JOUR. T1 - Presenilin modulates EGFR signaling and cell transformation by regulating the ubiquitin ligase Fbw7. AU - Rocher-Ros, V.. AU - Marco, S.. AU - Mao, J. H.. AU - Gines, S.. AU - Metzger, D.. AU - Chambon, P.. AU - Balmain, A.. AU - Saura, C. A.. PY - 2010/5/20. Y1 - 2010/5/20. N2 - The epidermal growth factor receptor (EGFR) and Notch signaling pathways have antagonistic roles during epidermal differentiation and carcinogenesis. The molecular mechanisms regulating the crosstalk between EGFR and Notch during epidermal transformation are largely unknown. We found enhanced EGFR-dependent signaling, proliferation and oncogenic transformation caused by loss of presenilins (PS), the catalytic components of γ-secretase that generates the Notch1 intracellular domain (NICD). The underlying mechanism for abnormal EGFR signaling in PS-deficient cells involves γ-secretase-independent transcriptional upregulation of the E3 ubiquitin ligase Fbw7. Fbw7α, which targets NICD for degradation, ...

The transcription factor zinc-finger protein Miz1 represses TNF-α-induced JNK activation and the repression is relieved upon TNF-α stimulation. However, the underlying mechanism is incompletely understood. Here we report that Miz1 interferes with the ubiquitin conjugating enzyme (E2) Ubc13 for binding to the RING domain of TNF-receptor associated factor 2 (TRAF2), thereby inhibiting the ubiquitin ligase (E3) activity of TRAF2 and suppressing TNF-α-induced JNK activation. Upon TNF-α stimulation, Miz1 rapidly undergoes K48-linked polyubiquitination at Lys388 and Lys472 residues and subsequent proteasomal degradation in a TRAF2-dependent manner. Replacement of Lysine 388 and Lysine 472 by arginines generates a nondegradable Miz1 mutant, which significantly suppresses TNF-α-induced JNK1 activation and inflammation. Thus, our results reveal a molecular mechanism by which the repression of TNF-α-induced JNK activation by Miz1 is de-repressed by its own site-specific ubiquitination and ...

Human nucleoprotein 95 (NP95) is a member of a subfamily of RING-finger type E3 ubiquitin ligases and is encoded by the UHRF1 gene in humans. NP95 binds specifically to DNA and recruits a histone deacetylase to regulate gene expression. NP95 expression peaks at late G1 phase and continues during G2 and M phases of the cell cycle. It plays a major role in the G1/S transition by regulating topoisomerase II alpha and retinoblastoma (Rb) gene expression. NP95 also functions in the p53-dependent response to DNA damage, and its expression is upregulated in lymphomas induced by radiation. NP95 is also known as ubiquitin-like with PHD and ring finger domains 1 (UHRF1), ubiquitin-like PHD and RING finger domain-containing protein 1, RING finger protein 106 (RNF106), inverted CCAAT box-binding protein of 90 kDa (ICBP90), nuclear zinc finger protein Np95, E3 ubiquitin-protein ligase UHRF1, hUHRF1, hNP95, HuNp95, and FLJ21925.. ...

Human nucleoprotein 95 (NP95) is a member of a subfamily of RING-finger type E3 ubiquitin ligases and is encoded by the UHRF1 gene in humans. NP95 binds specifically to DNA and recruits a histone deacetylase to regulate gene expression. NP95 expression peaks at late G1 phase and continues during G2 and M phases of the cell cycle. It plays a major role in the G1/S transition by regulating topoisomerase II alpha and retinoblastoma (Rb) gene expression. NP95 also functions in the p53-dependent response to DNA damage, and its expression is upregulated in lymphomas induced by radiation. NP95 is also known as ubiquitin-like with PHD and ring finger domains 1 (UHRF1), ubiquitin-like PHD and RING finger domain-containing protein 1, RING finger protein 106 (RNF106), inverted CCAAT box-binding protein of 90 kDa (ICBP90), nuclear zinc finger protein Np95, E3 ubiquitin-protein ligase UHRF1, hUHRF1, hNP95, HuNp95, and FLJ21925.. ...

Emerging and preclinical drugs. Because the field of Ub biology is still burgeoning, many of the intermolecular interactions between specific Ub enzymes and their cognate substrates are either newly characterized or unknown. While a few drugs have been developed to specifically antagonize E2-conjugating enzymes, E3 ligases, and DUBs, none of these have yet entered advanced clinical trials (Table 1). The ubiquitination activity of some E3 ligases requires the activity of other proteins. In particular, the cullin-RING E3 ligases require covalent binding of the Ub-like protein NEDD8 to the cullin component of the E3 ligase for proper function. The compound MLN4924 is a potent inhibitor of NEDD8 activation, and the drug has been shown in multiple preclinical models to effectively block neoplastic cell proliferation (32). Phase I trials of this agent have been completed for non-hematologic malignancies, and other trials are underway or planned for the use of this drug in an array of hematologic ...

Mitophagy is a key process regulating mitochondrial quality control. Several mechanisms have been proposed to regulate mitophagy, but these have mostly been studied using stably expressed non-native proteins in immortalized cell lines. In skeletal muscle, mitophagy and its molecular mechanisms require more thorough investigation. To measure mitophagy directly, we generated a stable skeletal muscle C2C12 cell line, expressing a mitophagy reporter construct (mCherry-green fluorescence protein-mtFIS1 101-152). Here, we report that both carbonyl cyanide m-chlorophenyl hydrazone (CCCP) treatment and adenosine monophosphate activated protein kinase (AMPK) activation by 991 promote mitochondrial fission via phosphorylation of MFF and induce mitophagy by ~20%. Upon CCCP treatment, but not 991, ubiquitin phosphorylation, a read-out of PTEN-induced kinase 1 (PINK1) activity, and Parkin E3 ligase activity toward CDGSH iron sulfur domain 1 (CISD1) were increased. Although the PINK1-Parkin signaling pathway ...

Last August we vacationed with friends in a house on Cape Cod, and on the first day, I dove in the water with my cell phone in my pocket. Oops! Spending the week as the only deviceless adult left me curiously out of sync with the others. For instance: Were sitting in the living room, four Red Sox fans watching baseball. Well, Im watching. The other three are busy with their handhelds. Jon checks in with work, Dan Sr. catches up on email, and Dan Jr. chases down Red Sox trivia questions. Who hit the homer that tied Game 6 of the 75 Series? (Bernie Carbo.) Is Tim Wakefield really both the winningest and the losingest active pitcher in baseball? (Yes.) Bit by bit our conversation becomes a sports quiz show, as the actual game goes on, semi-watched ...

Angelman Syndrome is a debilitating neurological disorder caused by mutation of the E3 ubiquitin ligase Ube3A, a gene whose mutation has als...

The transforming growth factor β (TGFβ) superfamily of signal transduction molecules plays crucial roles in the regulation of cell behavior. TGFβ regulates gene transcription through Smad proteins and signals via non-Smad pathways. The TGFβ pathway is strictly regulated, and perturbations lead to tumorigenesis. Several pathway components are known to be targeted for proteasomal degradation via ubiquitination by E3 ligases. Smurfs are well known negative regulators of TGFβ, which function as E3 ligases recruited by adaptors such as I-Smads. TGFβ signaling can also be enhanced by E3 ligases, such as Arkadia, that target repressors for degradation. It is becoming clear that E3 ligases often target multiple pathways, thereby acting as mediators of signaling cross-talk. Regulation via ubiquitination involves a complex network of E3 ligases, adaptor proteins, and deubiquitinating enzymes (DUBs), the last-mentioned acting by removing ubiquitin from its targets. Interestingly, also non-degradative ...

Looking for online definition of aminoacid-tRNA ligases in the Medical Dictionary? aminoacid-tRNA ligases explanation free. What is aminoacid-tRNA ligases? Meaning of aminoacid-tRNA ligases medical term. What does aminoacid-tRNA ligases mean?

NF-kappaB transcription factor is activated upon ubiquitination and subsequent proteolysis of its inhibitor IkappaB. The phosphorylation-dependent ubiquitination is mediated by SCF E3 ubiquitin ligase. In this study, we identified a novel murine F-box/WD40 repeat-containing protein, mHOS (a homologue of HOS/betaTrCP2). mHOS efficiently binds Skp1 protein (a core component of SCF ubiquitin ligase), and phosphorylated IkappaB(alpha). We found that mHOS associates with SCF-ROC1 E3 ubiquitin ligase activity. We have also observed that mHOS is overexpressed in chemically-induced mouse skin tumors, and its overexpression (but not accelerated IkappaB phosphorylation) coincides with the accelerated degradation of IkappaB in vivo. The role of mHOS in the constitutive activation of NF-kappaB in skin carcinogenesis is discussed. ...

DNA ligase 1 is an enzyme that in humans is encoded by the LIG1 gene. DNA ligases are important tools for DNA replication and repair in living organisms. There are two families of DNA ligases, ATP-dependent DNA ligases and NAD+ dependent DNA ligases. Dependence upon ATP or NAD+ is conferred in the ligase-adenylate formation and which substrate is to be used. ATP dependent ligases are found in eukaryotes, while NAD+ dependent ligases are found in prokaryotes. DNA ligase I is found in eukaryotes and therefore is in the family of ATP-dependent DNA ligases. Previously it had been known that DNA replication occurred through the breakage of the double DNA strand, but the mechanism of action and enzyme responsible for ligating the strands back together was unknown. In the 1960s Lehman laboratories investigated this mystery, discovering DNA ligase and its mechanism of action in 1967. The Gellert, Richardson, and Hurwitz laboratories are also credited for their help in the discovery of DNA ligases in the ...

We identified a protein degradation pathway at the INM in yeast mediated by the Asi complex. The Asi complex functions together with the ubiquitin-conjugating enzymes Ubc6 and Ubc7 to degrade soluble and integral membrane proteins. Genetic evidence suggests that the Asi ubiquitin ligase defines a pathway distinct from, but complementary to, ERAD. Using unbiased screening with a novel genome-wide yeast library based on a tandem fluorescent protein timer, we identify more than 50 substrates of the Asi, Hrd1 and Doa10 E3 ubiquitin ligases. We show that the Asi ubiquitin ligase is involved in degradation of mislocalized integral membrane proteins, thus acting to maintain and safeguard the identity of the INM.. ​. Khmelinskii A, Blaszczak E, Pantazopoulou M, Fischer B, Omnus DJ, Le Dez G, Brossard A, Gunnarsson A, Barry JD, Meurer M, Kirrmaier D, Boone C, Huber W, Rabut G, Ljungdahl PO & Knop M (2014) Protein quality control at the inner nuclear membrane. Nature 516: 410-413 ...

DNA ligases are enzymes that seal breaks in the backbones of DNA, leading to them being essential for the survival of all organisms. DNA ligases have been studied from many different types of cells and organisms and shown to have diverse sizes and sequences, with well conserved specific sequences that are required for enzymatic activity. A significant number of DNA ligases have been isolated or prepared in recombinant forms and, here, we review their biochemical and structural characterization. All DNA ligases contain an essential lysine that transfers an adenylate group from a co-factor to the 5′-phosphate of the DNA end that will ultimately be joined to the 3′-hydroxyl of the neighbouring DNA strand. The essential DNA ligases in bacteria use β-nicotinamide adenine dinucleotide (β-NAD+) as their co-factor whereas those that are essential in other cells use adenosine-5′-triphosphate (ATP) as their co-factor. This observation suggests that the essential bacterial enzyme could be targeted ...

FIGURE 1. E3 ubiquitin ligases and DUBs involved in CD4+ T cell identity. After T cell activation by an activated APC, a naive T cell can differentiate into any of the CD4+ effector cell fates shown. All of the key transcriptional factors that regulate these effector fates can be regulated directly or indirectly via ubiquitylation. ...

Here, we uncover a new class of substrates of the ERAD ubiquitin ligase Doa10. These are proteins that contain a hydrophobic hairpin and that localize to ER and LD membranes. By degrading specifically the ER pool, ERAD restricts their localization to LDs, thereby contributing to maintain the individual membrane identities of the ER and LDs. These findings reveal a function for the ERAD pathway that is distinct from its role in protein quality control or in lipid‐dependent degradation of sterol enzymes (Ruggiano et al, 2014). We call this novel function protein spatial control since it leads to the degradation of a protein based on its localization rather than its folding status.. The involvement of quality control systems in the degradation of mislocalized proteins has been described in different contexts. For example, tail‐ and GPI‐anchored proteins failing to insert in the ER membrane are selectively targeted for degradation (Hessa et al, 2011; Ast et al, 2014; Rodrigo‐Brenni et al, ...

DCUN1D5 (defective in cullin neddylation 1 domain containing 5), Authors: Dessen P. Published in: Atlas Genet Cytogenet Oncol Haematol.

634 The ubiquitin-proteasome pathway plays a major role in cancer development and is a bona fide target for cancer therapy. The covalent attachment of ubiquitin to a target protein proceeds through a multi-enzyme cascade. Initially, E1 activates ubiquitin and is then transferred to a cysteine residue of an E2 ubiquitin-conjugating enzyme (ubc). Finally, the E2 itself, or more commonly in concert with an E3 ubiquitin ligase, ligates the ubiquitin via its carboxy terminus to lysine residues of a protein substrate. This enzymatic cascade, responsible for ubiquitylating target proteins is complex, and its regulation is only beginning to be understood. The complexity stems from the large number of E2 and E3 enzymes; in humans, more than 30 E2s and hundreds of putative E3 ligases have been identified. The enzymatic nature, multitude of E2 and E3s and their specific substrate recognition predestines them as therapeutic targets in major diseases.. Targeting components of ubiquitination pathway for drug ...

The enzymes of the ubiquitylation pathway play a pivotal role in a number of cellular processes including regulated and targeted proteasomal degradation of substrate proteins. Three classes of enzymes are involved in the process of ubiquitylation; activating enzymes (E1s), conjugating enzymes (E2s) and protein ligases (E3s). UBE2V2 is a member of the E2 conjugating enzyme family and cloning of the human gene was first described by Fritsche et al. (1997). UBE2V2 shares 90% sequence identity with UBE2V1 in its C-terminal domain (Sancho et al., 1998). The UEV protein Mms2 (yeast homologue of human UBE2V2) forms a heterodimer with yeast Ubc13 (UBE2N) which is recruited to chromatin by the RING finger proteins RAD5 and RAD18 in the RAD6 dependent post-replicative DNA repair pathway (Hofmann and Pickart 1999). These proteins also play a central role in the assembly of K63-linked polyubiquitin chains (Ulrich and Jentsch 2000; Xiao et al., 1998). UEV/Ubc complexes have been implicated in the assembly of ...

High-risk human papilloma viruses (HPV) cause the majority of anal, cervical, vaginal, vulvar, penile, and oropharyngeal cancers with an annual incidence of 630,000 cases worldwide. HPVs can cause dysplasia that increases neoplasia risk. HPVs encode eight major viral proteins with the E6 protein being crucial for replication. E6 binding to ubiquitin ligase E6AP initiates polyubiquitination of p53, targeting the protein for proteasomal degradation. We are taking a novel approach to inhibit HPV infection by designing inhibitors targeting the E6-E6AP binding pocket, thereby preventing p53 degradation and restoring its tumor suppressor function. To affirm interaction with the targeted binding site, we generated E6 point mutations that were designed to disrupt interaction with the compound. To ensure their suitability for our studies, we are herein characterizing their capacity to bind E6AP and degrade p53.. Methods: ...

DNA double-strand breaks (DSBs) not only interrupt the genetic information, but also disrupt the chromatin structure, and both impairments require repair mechanisms to ensure genome integrity. We showed previously that RNF8-mediated chromatin ubiquitylation protects genome integrity by promoting the accumulation of repair factors at DSBs. Here, we provide evidence that, while RNF8 is necessary to trigger the DSB-associated ubiquitylations, it is not sufficient to sustain conjugated ubiquitin in this compartment. We identified RNF168 as a novel chromatin-associated ubiquitin ligase with an ability to bind ubiquitin. We show that RNF168 interacts with ubiquitylated H2A, assembles at DSBs in an RNF8-dependent manner, and, by targeting H2A and H2AX, amplifies local concentration of lysine 63-linked ubiquitin conjugates to the threshold required for retention of 53BP1 and BRCA1. Thus, RNF168 defines a new pathway involving sequential ubiquitylations on damaged chromosomes and uncovers a functional ...

Cullin-based E3 ligases are a major subfamily of ubiquitin ligases and function in many biological processes. CUL4A and CUL4B, two paralogs in mammalian cells, coexpress in many cell types, share high sequence similarity, form separate E3 ligase complexes with the adapter proteins DDB1 and DDB2, and have redundant and distinct functions in promoting efficient NER (OConnell and Harper, 2007; Guerrero-Santoro et al., 2008; Liu et al., 2009). CUL4A-DDB1 also forms an E3 ligase complex with CSA. This complex interacts with CSB and functions in the TCR pathway (Fousteri et al., 2006). DCAF proteins interact directly with DDB1 through the WDxR motif in the WD40 domain in mammalian cells. The Arabidopsis genome encodes 119 putative DCAF proteins with 165 WDxR motifs (Lee et al., 2008; Zhang et al., 2008). However, only few of these proteins have been shown functionally to interact with CUL4-DDB1A (Bernhardt et al., 2006; Lee et al., 2008; Zhang et al., 2008; Molinier et al., 2008). In this study, we ...

Both ubiquitin‐ and receptor‐dependent mitophagy pathways have been described, and it has been speculated that there is cross‐talk between these two pathways. We demonstrated that FUNDC1 is a new substrate of the mitochondrial E3 ligase MARCH5 and that MARCH5‐mediated ubiquitylation and degradation of FUNDC1 is one of the early events in response to hypoxia. We show that MARCH5 mediates ubiquitylation of FUNDC1 at K119 to promote its proteasome‐dependent degradation under hypoxic stress. Our results suggest a new regulatory mechanism of FUNDC1‐mediated mitophagy, which is distinct from the Parkin‐mediated pathway. Indeed, hypoxia does not induce translocation of Parkin to mitochondria (Fig 1H), and FUNDC1 overexpression induces mitophagy in Parkin‐ or PINK1‐deficient cells (Y. Zhu, J. Han, unpublished data). It is somewhat surprising that Parkin, as a potent E3 ligase, does not mediate ubiquitylation or degradation of FUNDC1, although a previous report showed that FUNDC1 is ...

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