Werner syndrome (WS) is a premature aging disorder caused by WRN protein deficiency. Here, we report on the generation of a human WS model in human embryonic stem cells (ESCs). Differentiation of WRN-null ESCs to mesenchymal stem cells (MSCs) recapitulates features of premature cellular aging, a global loss of H3K9me3, and changes in heterochromatin architecture. We show that WRN associates with heterochromatin proteins SUV39H1 and HP1α and nuclear lamina-heterochromatin anchoring protein LAP2β. Targeted knock-in of catalytically inactive SUV39H1 in wild-type MSCs recapitulates accelerated cellular senescence, resembling WRN-deficient MSCs. Moreover, decrease in WRN and heterochromatin marks are detected in MSCs from older individuals. Our observations uncover a role for WRN in maintaining heterochromatin stability and highlight heterochromatin disorganization as a potential determinant of human aging. ...

Mechanisms contributing to the maintenance of heterochromatin in proliferating cells are poorly understood. We demonstrate that chromatin assembly factor 1 (CAF-1) binds to mouse HP1 proteins via an N-terminal domain of its p150 subunit, a domain dispensable for nucleosome assembly during DNA replication. Mutations in p150 prevent association with HP1 in heterochromatin in cells that are not in S phase and the formation of CAF-1-HP1 complexes in nascent chromatin during DNA replication in vitro. We suggest that CAF-1 p150 has a heterochromatin-specific function distinct from its nucleosome assembly function during S phase. Just before mitosis, CAF-1 p150 and some HP1 progressively dissociate from heterochromatin concomitant with histone H3 phosphorylation. The HP1 proteins reassociate with chromatin at the end of mitosis, as histone H3 is dephosphorylated.. ...

Species in the subgenus Artibeus Leach, 1821 are widely distributed in Brazil. Conserved karyotypes characterize the group with identical diploid number and chromosome morphology. Recent studies suggested that the heterochromatin distribution and accumulation patterns can vary among species. In order to assess whether variation can also occur within species, we have analyzed the chromosomal distribution of constitutive heterochromatin in A. planirostris (Spix, 1823) and A. lituratus (Olfers, 1818) from Central Amazon (North Brazil) and contrasted our findings with those reported for other localities in Brazil. In addition, Ag-NOR staining and FISH with 18S rDNA, telomeric, and LINE-1 probes were performed to assess the potential role that these different repetitive markers had in shaping the current architecture of heterochromatic regions. Both species presented interindividual variation of constitutive heterochromatin. In addition, in A. planirostris the centromeres of most chromosomes are enriched

While Su(var)3-9, Su(var)3-7, and HP1a reciprocal interactions are well documented at pericentric regions (Schotta et al. 2002; Greil et al. 2003; Danzer and Wallrath 2004) they are not universal. For example, HP1 binding on the fourth chromosome has been shown to be independent of Su(var)3-9 (Schotta et al. 2002), and Danzer and Wallrath (2004) using a tethering system to recruit HP1a to euchromatic sites have shown that HP1a-mediated silencing can operate in a Su(var)3-9-independent manner. Moreover, Deng et al. (2007) have provided evidence that at least two different molecular mechanisms regulate Su(var)3-9 localization, one dependent on HP1 and one dependent on the JIL-1 kinase. These findings indicate that although Su(var)3-9, Su(var)3-7, and HP1a cooperate in heterochromatin formation and gene silencing at pericentric chromosome sites, they may function independently at other regions such as the chromosome arms. In this study we show that the lethality but not the chromosome morphology ...

Normal cell division requires faithful DNA replication and proper DNA segregation in order to generate two identical daughter cells. Within cells DNA is always assembled with positively charged histones to form protein-DNA packaging structures called chromatin. The order of chromatin packaging regulates cellular functions including replication, gene expression and chromosome segregation. The compact chromatin region is called heterochromatin. The centromere is a rigid, gene-silent heterochromatin region and is essential for faithful chromosome segregation. To duplicate a cell, this region needs to be unpacked for replication and further be reassembled to maintain its function. I tackled how cells maintain faithful replication and reassembly at this region in S. pombe. ❧ I found that a replication protein Cdc18/Cdc6 associates with heterochromatin protein Swi6/HP1. A mutation cdc18-I43A that reduces Cdc18 association with Swi6 has no silencing defect at the centromere, but changes Swi6 ...

Structure wise, facultative heterochromatin is enriched with LINE sequences. and Georgatos, S.D. Despite being known for over 50 years, relatively few components of the Barr body have been identified. Calico or Tortoiseshell cat with mosaic fur (Photo Credit : Cheryl Toepfer/Shutterstock). XCI is facilitated by the upregulation of the long non-coding RNA gene, XIST, which coats its chromosome of origin, recruits heterochromatin factors, and silences gene expression. Females. The composition of the Barr body has been a matter of some conjecture for over 50 years. What are Mutations and what are the different types of Mutations? 5A). (, Kourmouli, N., Theodoropoulos, P.A., Dialynas, G., Bakou, A., Politou, A.S., Cowell, I.G., Singh, P.B. In addition, the lack of HP1 enrichment at the mouse Xi (21) may reflect the absence of a Barr body state in mouse cultured cells (4). How Big Is It and Does It Bite? To investigate the possibility that the Barr body in different cells is elevated for different ...

Because C. elegans chromosomes are holocentric and lack centromeric heterochromatin, HP1 proteins are dispensable for chromosome segregation and mitotic viability in this organism [23, 25]. We have exploited this fact to examine in detail the role of one of the C. elegans HP1 homologues, HPL-2, in regulating developmental pathways of gene expression, a second physiological function ascribed to heterochromatin. By comparing the effects of hpl-2 deletion at different stages of development, we have shed light on a novel role for this HP1 family member in dauer diapause, longevity and lipid metabolism. These three processes have in common an extremely tight response to environmental factors. Thus, our data link a response to environmental factors to the epigenetic regulator HPL-2. At least some of the genes identified in this study are shown by CHIP-on chip to be bound by HPL-2, and are therefore likely to represent direct targets.. We show that hpl-2 plays a role in the choice between dauer and ...

The SUMO protease SENP7 was recently proven to interact straight with Horsepower1 also to enable Horsepower1 retention and accumulation at pericentric heterochromatin without affecting H3K9me3 amounts (Maison et al, 2012; Romeo et al, 2015). bindings, SYCE2 interacts using the chromoshadow domains of Horsepower1 through its N-terminal hydrophobic series. SYCE2 reduces Horsepower1-H3K9me3 FN-1501 binding without impacting H3K9me3 amounts and potentiates ataxia telangiectasia mutatedCmediated double-strand break fix activity also in the lack of exogenous DNA harm. Such a somatic function of SYCE2 is noticed also if its expression levels are low ubiquitously. These findings claim that SYCE2 has a somatic function in the hyperlink between your nuclear microenvironment as well as the DNA harm response potentials being a scaffold of HP1 localization. Launch Meiosis is certainly a cell department procedure exclusive to germ cells and possesses some particular features distinctive from mitosis. The ...

The DNA in eukaryotes is arranged in fibres of chromatin. The chromatin may be more or less compacted and the degree of condensation of the chromatin affects the accessibility of the DNA. The accessibility of the DNA, in turn, affects transcription and gene regulation. Genes within inaccessible DNA are commonly repressed whereasgenes within accessible DNA are active and expressed. This thesis concerns the interplay between chromatin and transcription with focus on the function of the RNA polymerase II (pol II) subunit Rpb7. We have demonstrated that processing of centromeric transcripts by the ribonuclease III family protein Dcr1 is required for heterochromatin formation at the centromeres of Schizosaccharomyces pombe. A point mutation in the pol II subunit Rpb7 caused a specific defect in centromeric heterochromatin formation. We have shown i) that the centromeric transcripts that accumulate in dcr1delta cells are products of pol II, ii) the rpbG150D mutation is deficient in recognition and/or ...

In response to metabolic or environmental stress, cells activate powerful defense mechanisms to prevent the formation and accumulation of toxic protein aggregates. The main orchestrator of this cellular response is HSF1 (heat shock factor 1), a transcription factor involved in the up-regulation of protein-coding genes with protective roles. It has become very clear that HSF1 has a broader function than initially expected. Indeed, our previous work demonstrated that, upon stress, HSF1 activates the transcription of a non-coding RNA, named Satellite III, at pericentromeric heterochromatin. Here, we observe that the function of HSF1 extends to telomeres and identify subtelomeric DNA as a new genomic target of HSF1. We show that the binding of HSF1 to subtelomeric regions plays an essential role in the upregulation of non-coding TElomeric Repeat containing RNA (TERRA) transcription upon heat shock. Importantly, our data show that telomere integrity is impacted by heat shock and that telomeric DNA ...

Thus, Th17 differentiation requires active modulation of IL-2 expression both by cell-extrinsic and cell-intrinsic mechanisms.. The present paper from Kuchroos lab shows that, through STAT3 and AhR induction, Aiolos bounds to and silences the Il2 locus, suppressing the production of IL-2 and promoting Th17 differentiation in vitro and in vivo. The members of the Ikaros family are quite interesting since they directly promote transcription on some loci, but also have a strong impact on chromatin modification and can also actively silence genes by associating them to centromeric heterochromatin regions. And indeed, in Aiolos-deficient Th17 cells, the Il2 promoter was characterized by epigenetic modifications associated with active gene expression.. This is a formal demonstration of a role for an Ikaros family member in T cell differentiation ...

Core component of the CAF-1 complex, a complex thought to mediate chromatin assembly in DNA replication and DNA repair. Assembles histone octamers onto replicating DNA in vitro. CAF-1 performs the first step of the nucleosome assembly process, bringing newly synthesized histones H3 and H4 to replicating DNA; histones H2A/H2B can bind to this chromatin precursor subsequent to DNA replication to complete the histone octamer. CHAF1A binds to histones H3 and H4. It may play a role in heterochromatin maintenance in proliferating cells by bringing newly synthesized cbx proteins to heterochromatic DNA replication foci (By similarity).

To keep genome stability cells pack large portions of their genome into silent chromatin or heterochromatin. candida. The cryo-electron microscopy structure reveals the chromodomain of Chp1 binds the histone H3 lysine 9 methylated tail and the core of the nucleosome primarily histones H3 and H2B. Mutations in chromodomain of Chp1 loops which interact with the nucleosome core abolished this connection Moreover fission candida cells with Chp1 loop mutations have a defect in Chp1 recruitment and heterochromatin formation. This study reveals the structural basis for heterochromatic silencing and suggests that chromodomains could read histone code in the H3 tail and the nucleosome core which would provide an additional layer of rules. four chromodomain proteins are involved in heterochromatin formation and transcriptional gene silencing: Chp1 Chp2 Clr4 and Swi6. The chromodomain of Chp1 (Chp1CD) has the highest affinity for the H3K9me peptide and is essential for tethering the RITS complex to ...

Constitutive heterochromatin (HC) is important for maintaining chromosome stability, but also delays the repair of DNA double-strand breaks (DSBs). DSB repair in complex mammalian genomes involves a fast phase (2-6 h) in which most of the breaks are rapidly repaired, and a slow phase (up to 24 h) in which the remaining damages in HC are repaired. We found that p53 deficiency delays the slow-phase DNA repair after ionizing irradiation. p53 deficiency prevents downregulation of histone H3K9 trimethylation at the pericentric HC after DNA damage. Moreover, p53 directly induces expression of the H3K9 demethylase Jumonji domain 2 family demethylase (JMJD2b) through promoter binding. The p53 activation also indirectly downregulates expression of the H3K9 methyltransferase SUV39H1. Depletion of JMJD2b or sustained expression of SUV39H1 delays the repair of HC DNA and reduces clonogenic survival after ionizing irradiation. The results suggest that by regulating JMJD2b and SUV39H1 expression, p53 not only ...

Cells were treated with either UVA or TMP/UVA. a Sequential IP demonstrates association of early-replicating Alu sequences with DONSON and late-replicating Satellite 3 sequences with FANCM. LINE-1 elements replicate throughout the S phase and are found in all fractions. Representative blot (n = 3). b DONSON interaction with the H3K4me3 euchromatin mark is more frequent in early S phase cells than in late S phase, while there is little interaction with the H3K9me3 heterochromatin mark in either stage. Sorted early and late S phase cells were examined by PLA. Scored nuclei: PLA between GFP-D: H3K4me3 of early S phase = 67, late S phase = 64, PLA between GFP-D: H3K9me3 of early S phase = 70, late S phase = 85, from three biological replicates. Data are mean ± s.e.m. c FANCM interaction with H3K9me3 heterochromatin mark is biased toward late S phase, while there is low interaction frequency with H3K4me3 in either stage. Scored nuclei: PLA between FANCM: H3K4me3 of early S phase = 64, late S phase = ...

Mammalian telomeres are inherently heterochromatic. While enhanced telomere maintenance is evident in malignant cancers, some cancers appear to maintain telomeres by neither the common telomerase nor the alternative telomere repeat recombination mechanisms. Specifically, the roles of epigenetic modifications in telomere protection are largely unknown in human cancers. I have combined newly developed cellular and molecular approaches to show that in some cancer cell types, experimentally enhanced heterochromatinization localized specifically at telomeres reduced damage-induced foci at telomeres, suggesting augmentation of telomere stability. These results lead to the intriguing hypothesis that manipulating the epigenetic status at telomeres may be exploited to elicit damage at the telomeres of cancer cells as a novel approach to fight cancer. My current work in progress focuses on identifying novel chromatin modifiers that weaken telomere protection by modulating telomere compaction. It is ...

Sideridou M, Zakopoulou R, Evangelou K, Liontos M, Kotsinas A, Rampakakis E, Gagos S, Kahata K, Grabusic K, Gkouskou K, Trougakos IP, Kolettas E, Georgakilas AG, Volarevic S, Eliopoulos AG, Zannis-Hadjopoulos M, Moustakas A, Gorgoulis VG J. Cell Biol. 195 (7) 1123-1140 [2011-12-26; online 2011-12-28] E-cadherin (CDH1) loss occurs frequently in carcinogenesis, contributing to invasion and metastasis. We observed that mouse and human epithelial cell lines overexpressing the replication licensing factor Cdc6 underwent phenotypic changes with mesenchymal features and loss of E-cadherin. Analysis in various types of human cancer revealed a strong correlation between increased Cdc6 expression and reduced E-cadherin levels. Prompted by these findings, we discovered that Cdc6 repressed CDH1 transcription by binding to the E-boxes of its promoter, leading to dissociation of the chromosomal insulator CTCF, displacement of the histone variant H2A.Z, and promoter heterochromatinization. Mutational analysis ...

Another interesting observation concerns the association of Orc1p* with heterochromatin in mid and late G1. The association of ORC with transcriptionally silenced, late replicating portions of the genome has been observed in other organisms, where ORC seems to play an active role in the assembly of these chromatin conformations. In the yeast S. cerevisiae, ORC binding to an ARS element is required for the recruitment of Sir factors and hence for the transcriptional silencing of the HML locus (Vujcic et al., 1999). In Drosophila, mutations of Orc2p were shown to perturb HP1 localization (Huang et al., 1998; Pak et al., 1997). Finally, it has been reported that human Orc2p binds in vivo to α-satellite sequences that compose pericentric heterochromatin (Keller et al., 2002). We have added a few molecular details to the characterization of the association of Orc1p with heterochromatin and we have identified two protein domains that are involved in this phenomenon. The first one (amino acids ...

Autoimmune diseases are characterized by the presence of multiple autoantibodies that react with components of nuclear, cytoplasmic, or surface origin (for review see Nakamura and Tan, 1992; Fritzler, 1997). In clinical medicine, autoantibodies have been used to establish diagnosis, estimate prognosis, follow the progression of a specific autoimmune disease, and, finally, increase our knowledge of the pathophysiology of autoimmunity. In cell biology, autoantibodies have been extremely useful as probes for the identification of novel proteins and isolation of their corresponding genes. Human autoimmune sera have been particularly useful in the study of the eukaryotic nucleus where they have identified a wide range of nuclear antigens, including both single- and double-stranded DNA, RNA, histones, small nuclear RNA-binding proteins, transcription factors, nuclear lamins, heterochromatin-associated proteins, topoisomerase I and II, and centromere proteins (Tan, 1989, 1991; Earnshaw and Rattner, ...

Kishigami and colleagues [19] were the first to report that TSA treatment improves full term development of mouse embryos obtained by transfer of cumulus cell nuclei. This was confirmed the same year by Rybouchkin and colleagues who reported a remarkable and significant 5-fold increase in the efficiency of cloning from cumulus cells with a transient TSA treatment for 10 hours post activation [20]. In their initial work, Rybouchkin and colleagues suggested that increased acetylation of histones after TSA treatment was linked to the improved developmental rates [20]. In the present work, we confirm the reproducibility of the beneficial effects of TSA treatment on long term developmental potential using another mouse strain and different culture conditions, as reflected by a significantly higher birth rate of live pups. In our laboratory, 3.1% of the TSA-treated SCNT embryos developed to term, which is identical to the 3.1% of clones obtained from ES cells [26] and ten times higher than the ...

The segregation distortion phenomenon occurs in Drosophila melanogaster males carrying an SD second chromosome and an SD+ homolog. In such males the SD chromosome is transmitted to the progeny more frequently than the expected 50% because of an abnormal differentiation of the SD+-bearing sperms. Three major loci are involved in this phenomenon: SD and Rsp, associated with the SD and SD+ chromosome, respectively, and E(SD). In the present work we performed a cytogenetic analysis of the Rsp locus which was known to map to the centromeric heterochromatin of the second chromosome. Hoechst- and N-banding techniques were used to characterize chromosomes carrying Responder insensitive (Rspi), Responder sensitive (Rsps) and Responder supersensitive (Rspss) alleles. Our results locate the Rsp locus to the h39 region of 2R heterochromatin. This region is a Hoechst-bright, N-banding negative heterochromatic block adjacent to the centromere. Quantitative variations of the h39 region were observed. The ...

Publications related to biomolecular condensates, phase separation, llps and more. Developing strategies to activate tumor-cell-intrinsic immune response is critical for improving tumor immunotherapy by exploiting tumor vulnerability. KDM4A, as a histone H3 lysine 9 trimethylation (H3K9me3) demethylase, has been found to play a critical role in squamous cell carcinoma (SCC) growth and metastasis. Here we report that KDM4A inhibition promoted heterochromatin compaction and induced DNA replication stress, which elicited antitumor immunity in SCC. Mechanistically, KDM4A inhibition promoted the formation of liquid-like HP1γ puncta on heterochromatin and stall DNA replication, which activated tumor-cell-intrinsic cGAS-STING signaling through replication-stress-induced cytosolic DNA accumulation. Moreover, KDM4A inhibition collaborated with PD1 blockade to inhibit SCC growth and metastasis by recruiting and activating CD8+ T cells. In vivo lineage tracing demonstrated that KDM4A inhibition plus PD1 blockade

Fu et al. demonstrate a requirement for the heterochromatin factors CMT and DDM1 in RNA-directed DNA methylation in maize. Plant Cell https://doi.org/10.1105/

The constitutive heterochromatin of the centromere is marked by high levels of tri-methylated histone H3 Lysine 9 (H3K9) and binding of the heterochromatin protein 1 (HP1), which are thought to also have an important role in mitosis. Histone deacetylase inhibitors (HDACi) are a class of anticancer agents which affect many cellular processes, including mitosis. Here we examine the mechanism by which these drugs disrupt mitosis. We have used Drosophila embryos to demonstrate that treatment with the HDACi 100 μg/ml suberic bishydroxamic acid (SBHA, IC50 12 μg/ml), conditions that induce extensive H3K9 acetylation and aberrant mitosis in mammalian cells, induced aberrant mitosis in the absence of de novo transcription. We have examined the effect of the same treatment on the levels of H3K9 modification and HP1 binding in human cancer cells, and found only minor effects on H3K9 methylation and HP1 binding. Complete loss of tri-methylated H3K9 or depletion of HP1α and β had no effect on mitosis, ...

This chapter provides a general description of the types of genetic variation caused by transposable elements in animals and plants, and examines this variation within an evolutionary framework. It focuses on the variation induced by transposable elements in their host organisms. The host variation associated with transposable elements can result from several interconnected aspects of transposable element activity. Estimates of the frequencies of new transposable element-induced mutations have been made under laboratory conditions and varied over an enormous range. The partial or complete sterility associated with several systems of hybrid dysgenesis in Drosophila provides an interesting aspect of variation associated with transposable element activity. Heterochromatin proteins can recognize and silence transposable elements, some of which target heterochromatin for insertion. Thus, the evolution of heterochromatin could have led to a self-perpetuating expansion of domains rich in transposable elements.

Facioscapulohumeral muscular dystrophy (FSHD) is an enigmatic disease associated with epigenetic alterations in the subtelomeric heterochromatin of the D4Z4 macrosatellite repeat. Each repeat unit encodes DUX4, a gene that is normally silent in most tissues. Besides muscular loss, most patients suff …

Studencka, M.; Konzer, A.; Moneron, G.; Wenzel, D.; Opitz, L.; Salinas-Riester, G.; Bedet, C.; Krüger, M.; Hell, S. W.; Wisniewski, J. R. et al.; Schmidt, H.; Palladino, F.; Schulze, E.; Jedrusik-Bode, M. A.: Novel roles of Caenorhabditis elegans heterochromatin protein HP1 and linker histone in the regulation of innate immune gene expression. Molecular and Cellular Biology 32 (2), S. 251 - 265 (2012 ...

Studencka, M.; Konzer, A.; Moneron, G.; Wenzel, D.; Opitz, L.; Salinas-Riester, G.; Bedet, C.; Krüger, M.; Hell, S. W.; Wisniewski, J. R. et al.; Schmidt, H.; Palladino, F.; Schulze, E.; Jedrusik-Bode, M. A.: Novel roles of Caenorhabditis elegans heterochromatin protein HP1 and linker histone in the regulation of innate immune gene expression. Molecular and Cellular Biology 32 (2), pp. 251 - 265 (2012 ...

We also examined the H3-K9 methylation status of centromeric regions at the molecular level by native chromatin immunoprecipitation (NChIP). Compared with the classical formaldehyde cross-linked chromatin immunoprecipitation technique, this procedure has the advantage of avoiding the formaldehyde cross-linking step that can fix chromatin interactions that are transient or simply due to spatial proximity. For NChIP, native oligonucleosomes were prepared and purified after Mnase digestion of mouse cell nuclei (ONeill and Turner, 1995) to obtain a high enrichment in mononucleosome on bulk DNA visualized by EtBr (Fig. 4 C, Bulk DNA). Consistently, with the supposedly heterochromatic nature of centromeric regions, we find that these regions were more resistant to digestion, as attested by the detection of larger fragments when probing for major and to a lesser extent for minor satellite repeats when compared with bulk DNA (Fig. 4 C, compare minor and major to bulk). Detection of the larger ...

TY - JOUR. T1 - Precise centromere mapping using a combination of repeat junction markers and chromatin immunoprecipitation-polymerase chain reaction. AU - Luce, Amy C.. AU - Sharma, Anupma. AU - Mollere, Oliver S.B.. AU - Wolfgruber, Thomas K.. AU - Nagaki, Kiyotaka. AU - Jiang, Jiming. AU - Presting, Gernot G.. AU - Dawe, R. Kelly. PY - 2006/11/6. Y1 - 2006/11/6. N2 - Centromeres are difficult to map even in species where genetic resolution is excellent. Here we show that junctions between repeats provide reliable single-copy markers for recombinant inbred mapping within centromeres and pericentromeric heterochromatin. Repeat junction mapping was combined with anti-CENH3-mediated ChIP to provide a definitive map position for maize centromere 8.. AB - Centromeres are difficult to map even in species where genetic resolution is excellent. Here we show that junctions between repeats provide reliable single-copy markers for recombinant inbred mapping within centromeres and pericentromeric ...

The DEK oncoprotein is a chromatin architectural factor that has essential functions in the maintenance of heterochromatin integrity. It is an abundant and unique chromatin constituent showing no sequence homology to any other known protein, and is highly conserved among multicellular eukaryotes. DEK binds to DNA, RNA, and interacts with various chromatin components including histones. The affinity of DEK to its binding partners is determined by posttranslational modifications, predominantly by phosphorylation as well as poly(ADP-ribosyl)ation. When interacting with DNA, DEK preferentially binds to cruciform DNA structures which arise during perturbed DNA replication and the repair of DNA strand breaks.,br /,,br /,,br /,Several lines of evidence, among others the frequent overexpression in highly malignant tumors and the positive correlation between DEK expression levels and chemoresistance, have led to the definition of DEK as a bona fide oncogene. On the other hand, investigation of a ...

The sequencing of the human genome revealed that the C2H2-zinc finger proteins (ZFPs) are the largest family of human transcription factors. Around 300 members of this family contain, in addition to their zinc finger motifs, a KRAB domain that has been implicated in transcriptional repression. It is thought that KRAB-ZFPs mediate this effect through the recruitment of the corepressor KAP1, which induces facultative heterochromatin through the activity of several associated chromatin-modifying factors. Our studies focused on the elucidation of the molecular mechanisms of transcriptional repression induced by KRAB-ZFPs and KAP1. For this, we made use of the conditional binding activity of the KRAB-containing repressor tTRKRAB. This ectopic protein serves as a paradigm for endogenous KRAB-ZFP functions, as it depends on cellular KAP1 for transcriptional repression. tTRKRAB only binds to heterologous TetO sites in the absence of doxycycline, thus making repressor activity drug-regulated. When we targeted

Epigenetic modifications, such as acetylation, phosphorylation, methylation, ubiquitination, and ADP ribosylation, of the highly conserved core histones, H2A, H2B, H3, and H4, influence the genetic potential of DNA. The enormous regulatory potential of histone modification is illustrated in the vast array of epigenetic markers found throughout the genome. More than the other types of histone modification, acetylation and methylation of specific lysine residues on N-terminal histone tails are fundamental for the formation of chromatin domains, such as euchromatin, and facultative and constitutive heterochromatin. In addition, the modification of histories can cause a region of chromatin to undergo nuclear compartmentalization and, as such, specific epigenetic markers are non-randomly distributed within interphase nuclei. In this review, we summarize the principles behind epigenetic compartmentalization and the functional consequences of chromatin arrangement within interphase nuclei.. ...

Distinctive classes of small RNAs, 20 to 32 nucleotides long, play important regulatory roles for varied cellular processes. on small RNA cDNA library preparation and sequencing and ignited the finding of new users and families of small RNAs (15C24). Small RNAs, in association with their protein effector parts, mediate sequence-specific posttranscriptional and transcriptional gene rules. They control mRNA translation, stability and localization (examined in 87771-40-2 25, 26) and feed into processes that control 87771-40-2 transposons (examined in 27, 28) and heterochromatin structure (examined in 4, 29). This wide variety of functions activated great interest to recognize and characterize the tiny RNAs expressed in various organisms, cell and tissues types, in regular and disease state governments. Here we explain our protocols for the structure of little RNA libraries and their version for several high throughput sequencing strategies. The protocols result from strategies defined previously ...

Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epigenetic regulation, is stable and heritable. Therefore, analyzing methylation status may be less temporally dependent and more informative for evaluating lineage commitment. Here we analyzed the effect of mechanical stimulation on osteogenic differentiation by applying fluid shear stress for 24 hr to osteocytes and then applying the osteocyte-conditioned medium (CM) to progenitor cells. We analyzed gene expression and changes in DNA methylation after 24 hr of exposure to the CM using quantitative real-time polymerase chain reaction and bisulfite sequencing. With fluid shear stress stimulation, methylation decreased for both adipogenic and osteogenic markers, which typically increases availability of ...

Ikaros encodes a DNA-binding zinc finger protein that acts as a tumor suppressor in human leukemia. The essential components of Ikaros activity include DNA binding and transcriptional repression via chromatin remodeling. We have previously reported that Ikaros directly interacts with Protein Phosphatase 1 (PP1) and undergoes dephosphorylation at specific amino acids (Popescu et al. J Biol Chem 2009 284(20):13869). PP1-mediated dephosphorylation of Ikaros regulates its DNA-binding to probes derived from gamma satellites of pericentromeric heterochromatin, and controls subcellular, pericentromeric localization of Ikaros in vivo. We extended our studies to determine how PP1-mediated dephoshorylation of Ikaros controls Ikaros function in regulating the expression of its target genes. An Ikaros mutant that is unable to associate with PP1 (IK 465/7A), and consequently hyperphosphorylated was compared to the wild type Ikaros for: 1) DNA-binding affinity toward the promoters of Ikaros target genes; ...

Epigenetic mechanisms of gene regulation-chemical and conformational changes to DNA and the chromatin that bundles it-have had an important impact on genome organization and inheritance and on cell fate. These mechanisms are conserved in eukaryotes and provide an additional layer of information superimposed on the genetic code. Robert Martienssen, a pioneer in the study of epigenetics, investigates mechanisms involved in gene regulation and stem cell fate in yeast and model plants including Arabidopsis and maize. He and his colleagues have shed light on a phenomenon called position-effect variegation, caused by inactivation of a gene positioned near densely packed chromosomal material called heterochromatin. They have discovered that small RNA molecules arising from repeating genetic sequences program that heterochromatin. Martienssen and colleagues have described a remarkable process by which companion cells to sperm in plant pollen grains provide them with instructions that protect sperm DNA ...

Euchromatin is both transcriptionally and genetically active. Transitions between euchromatin and heterochromatin during DSB repair also impact transcription. Other DNA-containing material stains more lightly, diffusely across the interphase nucleus; it is called euchromatin. Histones are a family of proteins, described in Chapter 2.2, that form a complex with DNA called a nucleosome that is stabilized by the attraction of the negatively charged DNA to the positively charged histones. It is normal chromatin which possesses active genes. These findings help explain how TIP60 can be activated in transcriptionally active chromatin, which normally has low levels of H3K9me3. Pecinka et al. It is usually dispersed all around the nucleus and is replicated throughout the S phase. For example, in cancer cells tumor suppressor genes are hypermethylated resulting in unchecked cell growth (Baylin and Jones, 2011; Timp and Feinberg, 2013). Chromatin condensation is critical for maintaining transcriptional ...

Morphologically, there are two nuclear compartments: nuclear envelope and nucleoplasm. Nuclear envelope is the peripheral part of the nucleus that separates the interior of the nucleus, known as nucleoplasm, from the cytoplasm. Nucleoplasm-cytoplasm communication is regulated by nuclear pores, which are molecular complexes inserted in the nuclear envelope. In the nucleoplasm, DNA and associated proteins form the chromatin, which is referred as heterochromatin if it is highly condensed, or as euchromatin if it is loosely packaged. Heterochromatin and euchromatin are found in the same nucelus and the proportion of every of them depends on the type and physiological state of the cell. The nucleolus, a unique chromatin domain, is also found in the nucleoplasm, as well as other dense structures known as nuclear bodies, which are composed of chromatin and other proteins. Here, we could go into all the molecular processes involved in DNA transcription and replication, as well as gene regulation. In the ...

The X-IV translocation, [...], is shown to contain the wild-type allele, [...], at the white locus. This [...] has been replaced with a mutant gene, w, and a comparison of R([...])/w with R(w)/w[...] shows the former to give a variegated white phenotype while the latter is completely wild-type. It is concluded that the white variegation is due to an instability in the action of [...] when it is located in the rearranged chromosome ...

This year, our team attempted to engineer epigenetic control of gene expression. In eukaryotic cells, DNA is wound around nucleosomes, protein spools that consist of an octamer of histones. The DNA and protein together, termed chromatin, can be tightly packgaged (heterochromatin) or more loosely arranged (eucharomatin). The density of nucleosomal packaging is signaled by a host of histone modifying enzymes, and enforced by chromatin remodeling complexes. Euchromatin is accessible to the transcriptional machinery (active) while heterochromatin is inaccessible, and refractory to transcription (silenced).. In nature, the modulation of gene expression via the alteration of DNA structure is an incredibly powerful form of cellular memory. Indeed, epigenetic changes regulating genome-wide expression patterns can persist through multiple rounds of cell division and remain for the lifetime of the cell. This mechanism allows embryonic stem cells to differentiate into myriad cell types in higher ...

Heterochromatin, Drosophila, Drosophila Melanogaster, Chromatin, Gene, Chromosome, Genome, Histone, Proteins, Chromosomes, Maintenance, Methylation, Mutations, Position Effect Variegation, Egg, Lysine, Plays, Role, Chromosome 4, Euchromatin

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Uniprot: Component of heterochromatin that recognizes and binds histone H3 tails methylated at Lys-9 (H3K9me), leading to epigenetic repression. In contrast, it is excluded from chromatin when Tyr-41 of histone H3 is phosphorylated (H3Y41ph). Can interact with lamin-B receptor (LBR). This interaction can contribute to the association of the heterochromatin with the inner nuclear membrane. Involved in the formation of functional kinetochore through interaction with MIS12 complex proteins. more.. ...

In FSHD patient muscle, truncation of D4Z4 repeats does not significantly alter 4q35 localization to the heterochromatic rim. (A) Cytogenetic preparation of FSHD lymphoblastoid cells demonstrating different intensities of D4Z4 signals (green) at each 4q35 allele (red), permitting the mutant and wild-type alleles to be distinguished. (B) Both 4q35 alleles (green) in a mutant FSHD myoblast remain at the nuclear periphery depleted of hnRNA (red). (C) Localization of wild-type (arrow) and mutant (arrowhead) alleles in a FSHD myoblast using the same probes as in A. DAPI (blue) delineates the nucleus. (D) Quantitation of the localization of mutant (mut) versus wild-type (wt) allele in three FSHD myoblast cell lines (GM 17731, GM17899, and GM17869A) and in a normal myoblast line (50MB-1) before and after differentiation. 100 cells analyzed per sample. Localization of 4q35 (red) in a normal (E) and a FSHD myotube (F) with more intense D4Z4 signal (green) demarcating wild type versus weaker mutant 4q35 ...

This gene encodes an evolutionarily-conserved protein containing an N-terminal chromodomain and a C-terminal SET domain. The encoded protein is a histone methyltransferase that trimethylates lysine 9 of histone H3, which results in transcriptional gene silencing. Loss of function of this gene disrupts heterochromatin formation and may cause chromosome instability. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Aug 2013 ...

Researchers have shown the fundamental role of the heterochromatin protein 1a (HP1a) in the reorganization of the 3D chromatin structure after fertilization. By combining powerful Drosophila genetics with 3D genome modeling, they discovered that HP1a is required to establish a proper chromatin 3D structure at multiple hierarchical levels during early embryonic development.

Heterochromatin - chromatin organisation, lines the nuclear membrane at the pores. Euchromatin - threadlike, delicate, abundant in active transcribed cells, regions of DNA to be transcribed or duplicated, must be coiled before genetic code can be read.. All the human bodys nucleated cells contain 46 chromosomes (23 pairs). Contain all the information that governs all cellular activitys. DNA molecules - form of genes. DNA molecule regulate specific functions. blueprint determines synthesis of an RNA molecule or polypeptide. Not visible in non dividing cells. ...

New study finds the chromatin structures (heterochromatin and euchromatin) may not be determinate of whether genes in a particular region of a chromosome get expressed. | Cell And Molecular Biology

We report here the molecular and cytological characterization of two proteins, ScoHET1 and ScoHET2 (for Sciara coprophila heterochromatin), which associate to constitutive heterochromatin in the dipteran S. coprophila. Both proteins, ScoHET1 of 37 kDa and ScoHET2 of 44 kDa, display two chromodomain motifs that contain the conserved residues essential for the recognition of methylated histone H3 at lysine 9. We raised antibodies to analyze the chromosomal location of ScoHET1 and ScoHET2 in somatic and germline cells. In S. coprophila polytene chromosomes, both proteins associate to the pericentromeric regions and to the heterochromatic subterminal bands of the chromosomes. In germinal nuclei, ScoHET1 and ScoHET2 proteins distribute to the heterochromatic regions of the regular chromosome complement and are abundantly present along the heterochromatic germline-limited

Epigenetic implies changes in regulatory states of genes or genomic DNA without changes in DNA sequence. The archetypical epigenetic modification in eukaryotic genomes is the addition of a methyl group to the fifth carbon of cytosine to produce 5-methylcytosine (5meC) [1, 2], reviewed in [3]. Cytosine DNA methylation is an epigenetic modification that is shared by many eukaryotic organisms. Along with various other epigenetic modifications such as methylation, phosphorylation and acetylation of histone amino acids, cytosine methylation is an important regulator of biological processes including transposon silencing, heterochromatin organization, genomic imprinting, and gene expression.. The distribution of cytosine methylation is highly variable within plant genomes [4]. This overall methylation pattern, which is conserved among diverse plant taxa, is often described as mosaic, as it consists of interspersed methylated and unmethylated regions [5, 6]. The patterns of 5meC, mechanisms for de ...

This gene encodes a non-histone chromatin protein involved in many cellular processes, including regulation of inducible gene transcription, DNA replication, heterochromatin organization, integration of retroviruses into chromosomes, and the metastatic progression of cancer cells. HMGA1 proteins are quite small (~10-12 kDa) and basic molecules, and consist of three AT-hooks with the RGRP (Arg-Gly-Arg-Pro) core motif, a novel cross-linking domain located between the second and third AT-hook, and a C-terminal acidic tail characteristic for the HMG family comprising HMGA, HMGB and HMGN proteins. HMGA1-GFP fusion proteins are highly dynamic in vivo (determined using FRAP analysis), but in contrast also show nanomolar affinity to AT-rich DNA in vitro (determined biochemically), which might be explained due to the extensive post-transcriptional modifications in vivo. HMGA1 preferentially binds to the minor groove of AT-rich regions in double-stranded DNA using its AT-hooks. It has little secondary ...

Feulgen bands can be obtained at the sites of constitutive heterochromatin in the chromosomes of Anemone blanda, Fritillaria lanceolata and Scilla siberica, simply by means of a short or extended acid hydrolysis. Extended hydrolysis gives positive bands in A. blanda and F. lanceolata and negative bands in S. siberica. Short hydrolysis gives no bands in A. blanda and S. siberica but gives negative bands in F. lanceolata. The kind of Feulgen banding obtained is not correlated with the type of base richness of the heterochromatin DNA; rather, it is probably due to differences in the associated nucleoproteins. ...

Satellite DNA consists of highly repetitive and tandemly arranged DNA sequences (Charlesworth et al., 1994) which are considered the main components of constitutive heterochromatin and are usually located in the centromeric regions of chromosomes and, less frequently, in telomeres (Charlesworth et al., 1994; Ugarkovic and Plohl, 2002). Satellite DNAs are heterogeneous and no general function has been attributed to this DNA class. However, despite the terminology junk DNA frequently associated with these sequences (Orgel and Crick, 1980), several biological roles have been suggested for some satellite DNA families, such as regulation of both heterochromatin condensation and genetic expression (reviewed by Ugarkovic, 2005). Moreover, satellite DNAs are involved in the maintenance of functional centromeres in mammals (Willard, 1990) and might also be related to the late replication of centromeres (Csink and Henikoff, 1998).. The satellite DNA sequences evolve in a concerted manner (Dover, 1982) ...

Author Summary During growth and development, all plants and animals must replicate their DNA. This process is regulated to ensure that all sequences are completely and accurately replicated and is limited to S phase of the cell cycle. In the cell, DNA is packaged with histone proteins into chromatin, and both DNA and histones are subject to epigenetic modifications that affect chromatin state. Euchromatin and heterochromatin are chromatin states marked by epigenetic modifications specifying open and closed conformations, respectively. Using the model plant Arabidopsis thaliana, we show that the time at which a DNA sequence replicates is influenced by the epigenetic modifications to the surrounding chromatin. DNA replication occurs in two phases, with euchromatin replicating in early and mid S phase and heterochromatin replicating late. DNA replication time has been linked to gene expression in other organisms, and this is also true in Arabidopsis because more genes are active in euchromatin when

Chromatin is the template on which DNA-associated transactions take place in eukaryotic organisms. Nucleosomes consisting of the four histones H2A, H2B, H3 and H4 each organize 150bp of DNA and constitute a first layer of chromatin. The three-dimensional organization of chromatin as well as histone post-translational modifications (PTMs) regulate recruitment of chromatin-associated effector proteins (effectors). Heterochromatin protein 1 (HP1) is an effector associated with silenced genome regions. HP1 recognizes histone H3 trimethylated at lysine 9 (H3 K9me3) and can dimerize. This results in a protein with two binding domains allowing multivalent engagement of target chromatin. HP1 can further promote chromatin condensation and inter-fiber contacts. The effector p53 binding protein (53BP1) is a key regulator in the DNA damage repair pathway. It is known to target a trio of PTMs; H4 dimethylated at K20 (H4 K20me2), H2A(.X) ubiquitylated at K15 (H2A.X K15ub) and H2A.X phosphorylated at S139 ...

One of the factors limiting indefinite proliferation of somatic cells is telomere length [1], [2]. Indeed, the inability to fully replicate both strands of a linear DNA molecule is expected to lead to gradual shortening of telomeres in cells that do not express telomerase. Telomere shortening may be even more severe, if the replication machinery fails to reach the telomeric end. Indeed, the highly repetitive primary structure of telomeres [3], the presence of G‐quadruplexes [4], DNA-RNA hybrids [5], [6], and T‐loops [7], as well as the extensive telomeric heterochromatinization [8], challenge the process of terminal DNA replication and make telomeres prone to fork collapse, similar to common fragile sites [9], [10]. Fork collapse within a telomere is unlikely to be resolved by incoming forks or dormant forks, since human telomeres are thought to be devoid of replication origins. Instead, telomere replication is normally dependent on a single origin, located at the subtelomeric regions [11]. ...

One of the factors limiting indefinite proliferation of somatic cells is telomere length [1], [2]. Indeed, the inability to fully replicate both strands of a linear DNA molecule is expected to lead to gradual shortening of telomeres in cells that do not express telomerase. Telomere shortening may be even more severe, if the replication machinery fails to reach the telomeric end. Indeed, the highly repetitive primary structure of telomeres [3], the presence of G‐quadruplexes [4], DNA-RNA hybrids [5], [6], and T‐loops [7], as well as the extensive telomeric heterochromatinization [8], challenge the process of terminal DNA replication and make telomeres prone to fork collapse, similar to common fragile sites [9], [10]. Fork collapse within a telomere is unlikely to be resolved by incoming forks or dormant forks, since human telomeres are thought to be devoid of replication origins. Instead, telomere replication is normally dependent on a single origin, located at the subtelomeric regions [11]. ...

During the ripening of tomato fruit (Lycopersicon esculentum Mill Dahong) the ultrasturture of nucleus in pericarp cell was observed by freeze-fracture and transmission electron microscopy. It was found that before the onset of ripening (green mature, G), the volume of heterochromatin was 45% of nuclear volume (Plate Ⅰ1). From the onset of ripening (B stage), heterochromatin was dispersed and decreased in volume (Plate Ⅰ 2). At the turning stage the volume of heterochromatin decreased and was dispersed evenly (Plate Ⅰ 3). At the fully ripening and overripening stages, the nucleus became abnormal, and the structure of chromatin collapsed (Plate Ⅰ 4, 5). When the ripening of fruit was accelerated by treatment with ethylene at B stage, heterochromatin was converted into euchromatin and disappeared, and, in the meantime, the number of nuclear pore increased to that at advanced ripening stage (Plate Ⅰ 1-4). The effect of ethylene was eliminated by adding NBD, a competitive inhibitor of ethylene

The origin recognition complex (ORC) is an initiator protein for DNA replication, but also effects transcriptional silencing in Saccharomyces cerevisiae and heterochromatin function in Drosophila. It is not known, however, whether any of these functions of ORC is conserved in mammals. We report the identification of a novel protein, HBO1 (histone acetyltransferase binding to ORC), that interacts with human ORC1 protein, the largest subunit of ORC. HBO1 exists as part of a multisubunit complex that possesses histone H3 and H4 acetyltransferase activities. A fraction of the relatively abundant HBO1 protein associates with ORC1 in human cell extracts. HBO1 is a member of the MYST domain family that includes S. cerevisiae Sas2p, a protein involved in control of transcriptional silencing that also has been genetically linked to ORC function. Thus the interaction between ORC and a MYST domain acetyltransferase is widely conserved. We suggest roles for ORC-mediated acetylation of chromatin in control ...

Y chromosome chromodomain protein 2B, chromodomain protein, Y chromosome, 2 related, testis-specific chromodomain protein Y 2, testis-specific chromodomain protein Y protein 2 related, Y chromosome chromodomain protein 2B;;chromodomain protein, Y chromosome, 2 related;;testis-specific chromodomain protein Y 2;;testis-specific chromodomain protein Y protein 2 ...

One patient with 1q12 heterochromatin and euchromatin was normal while the other had minor dysmorphism. For patient D of this report, trisomy for the pericentric short arm euchromatin extending at least to the BAC923C6 only appears to be associated with mild dysmorphism. Presumably this region is gene poor or contains genes which do not significantly compromise function when present at an increased dosage.. Detailed comparison of the phenotypes of patients with accessory r(1)s which consist of euchromatin but where 1q12 heterochromatin is absent (category 3, table 2) are presented in table 1. Based on molecular cytogenetic analysis, only patient B is likely to contain a contiguous region of pericentric short arm euchromatin. Patients A and B are considered to possess ring chromosomes derived from non-contiguous regions of chromosome 1 and therefore are unlikely to share euchromatin between each other or with other patients. The origin of the euchromatin in the patient reported by Lanphearet al ...

A group of researchers from the University of California, Berkeley discovered that in mammals, males are XY and tend to live shorter lives than XX females. This is due to the Y chromosome as its genetic elements tend to jump around causing mutations. The Y chromosome densely packs DNA, called heterochromatin, keeps these elements in check. It is the heterochromatin when it deteriorates as organism age. This eventually plays a role in how long individuals live. As compared to females the heterochromatin in the genome stayed steady as compared to males this densely packed DNA was greatly reduced. The team, later on, created flies with abnormal numbers of Y chromosomes, and as a result, the females carrying the Y chromosomes and males with an extra Y did not live as long their wild types equivalents. Similar genetics elements were seen in these flies as in selfish, the males with no Y chromosome lived a lot longer than normal XY males. Drosophila aging is an attractive topic that is drawing many ...

Repeated DNA in heterochromatin presents enormous difficulties for whole-genome sequencing; hence, sequence organization in a significant portion of the genomes of multicellular organisms is relatively unknown. Two sequenced BACs now allow us to compare telomeric retrotransposon arrays from Drosophila melanogaster telomeres with an array of telomeric retrotransposons that transposed into the centromeric region of the Y chromosome ,13 MYA, providing a unique opportunity to compare the structural evolution of this retrotransposon in two contexts. We find that these retrotransposon arrays, both heterochromatic, are maintained quite differently, resulting in sequence organizations that apparently reflect different roles in the two chromosomal environments. The telomere array has grown only by transposition of new elements to the chromosome end; the centromeric array instead has grown by repeated amplifications of segments of the original telomere array. Many elements in the telomere have been ...

In by determining the degrees of K4-methylated H3, assaying the strength of gene silencing at the rDNA and using a genetic assessment of kinetochore function as a proxy for defects in Dam1 methylation. higher-order chromatin structures that promote compaction and protection of DNA. The structure of chromatin is dynamic to provide access to the underlying DNA template for nuclear processes, such as transcription and replication, and is controlled by several mechanisms [1]. Although the mechanisms of chromatin regulation by methylated histones are not as well understood as those governed by acetylated histones, a large body of work supports roles for methylated histones in the regulation of euchromatin and heterochromatin [2], [3], [4], [5]. Lysine-methylated histones can have diverse effects on transcription, ranging from regulation of Pol II initiation and elongation to the formation and maintenance of repressive heterochromatin [5], [6]. Histone methylation can be more complex than other ...

Tri- and dimethylations of histone H3K9 (H3K9me3/2) and H3K27 (H3K27me3/2), both situated in the A-R-Kme-S sequence motif, mediate transcriptional repression of distinct genomic regions. H3K9me3/2 mainly governs constitutive heterochromatin formation, while H3K27me3/2 represses key developmental genes. The mechanisms by which histone-modifying enzymes selectively regulate the methylation states of H3K9 and H3K27 are poorly understood. Here we report the crystal structures of the catalytic fragment of UTX/KDM6A, an H3K27me3/2-specific demethylase, in the free and H3 peptide-bound forms. The catalytic jumonji domain binds H3 residues 25-33, recognizing H3R26, H3A29, and H3P30 in a sequence-specific manner, in addition to H3K27me3 in the catalytic pocket. A novel zinc-binding domain, conserved within the KDM6 family, binds residues 17-21 of H3. The zinc-binding domain changes its conformation upon H3 binding, and thereby recognizes the H3L20 side chain via a hydrophobic patch on its surface, ...

A goal of molecular genetics is to understand the relationship between basic nuclear processes, epigenetic changes and the numerous proteins that orchestrate these effects. One such protein, ATRX, contains a highly conserved plant homeodomain (PHD)-like domain, present in many chromatin-associated proteins, and a carboxy-terminal domain which identifies it as a member of the SNF2 family of helicase/ATPases. Mutations in ATRX give rise to characteristic developmental abnormalities including severe mental retardation, facial dysmorphism, urogenital abnormalities and alpha-thalassaemia. This circumstantial evidence suggests that ATRX may act as a transcriptional regulator through an effect on chromatin. We have recently shown that ATRX is localized to pericentromeric heterochromatin during interphase and mitosis, suggesting that ATRX might exert other chromatin-mediated effects in the nucleus. Moreover, at metaphase, some ATRX is localized at or close to the ribosomal DNA (rDNA) arrays on the short arms of

Copyright 2013 by the Massachusetts General Hospital. Some sections copyright 2008-2009 by The President and Fellows of Harvard College.. ...

BACKGROUND & AIMS: Little is known about mechanisms that underlie postnatal hepatocyte maturation and fibrosis at the chromatin level. We investigated the transcription of genes involved in maturation and fibrosis in postnatal hepatocytes of mice, focusing on the chromatin compaction the roles of the Polycomb repressive complex 2 histone methyltransferases EZH1 and EZH2. METHODS: Hepatocytes were isolated from mixed background C57BL/6J-C3H mice, as well as mice with liver-specific disruption of Ezh1 and/or Ezh2, at postnatal day 14 and 2 months after birth. Liver tissues were collected and analyzed by RNA sequencing, H3K27me3 chromatin immunoprecipitation sequencing, and sonication-resistant heterochromatin sequencing (a method to map heterochromatin and euchromatin). Liver damage was characterized by histologic analysis. RESULTS: We found more than 3000 genes differentially expressed in hepatocytes during liver maturation from postnatal day 14 to month 2 after birth. Disruption of Ezh1 and Ezh2 ...

Chromatin is the complex combination of DNA and proteins that makes up chromosomes.[1][2] It is found inside the nuclei of eukaryotic cells. Chromatin is divided into heterochromatin (condensed) and euchromatin (extended) forms.[3][4] Heterochromatin is composed mostly of satellite DNA tandem repeats. The active components of chromatin are DNA and histone proteins, although other proteins also occur.[5] The functions of chromatin are: ...

The chromo domain was originally identified as a protein sequence motif common to the Drosophila chromatin proteins, Polycomb (Pc) and heterochromatin protein 1 [HP1; Paro and Hogness (1991) Proc. Natl. Acad. Sci. USA, 88, 263-267; Paro (1990) Trends Genet., 6, 416-421]. Here we describe a second chromo domain-like motif in HP1. Subsequent refined searches identified further examples of this chromo domain variant which all occur in proteins that also have an N-terminally located chromo domain. Due to its relatedness to the chromo domain, and its occurrence in proteins that also have a classical chromo domain, we call the variant the chromo shadow domain. Chromo domain-containing proteins can therefore be divided into two classes depending on the presence, for example in HP1, or absence, for example in Pc, of the chromo shadow domain. We have also found examples of proteins which have two classical chromo domains. The Schizosaccharomyces pombe SWI6 protein, involved in repression of the silent ...

Karyotype analyses in members of the four Cactaceae subfamilies were performed. Numbers and karyotype formula obtained were: Pereskioideae = Pereskiaaculeata(2n = 22; 10 m + 1 sm), Maihuenioideae = Maihuenia patagonica (2n = 22, 9 m + 2 sm; 2n = 44, 18 m + 4 sm), Opuntioideae = Cumulopuntia recurvat …

Polystachya Hook. consists of approximately 240 species, ranging over a wide geographic area. Up to now a very small number of papers dealing with molecular cytogenetics and phylogeny of the genus Polystachya were published. Last cytological analysis was made in year 1979 but it included only a small number of species. This research has involved the largest number of species so far, analyzing total number of 33 species from wide geographical area with the purpose of determining the correct number of chromosomes within the genus Polystachya. It was found that the genus Polystachya is very homogeneous in the context of chromosome number. Basic complement contains twenty chromosomes (x=20). Most of the species are diploids with 2n=2x=40 chromosomes, while 8 species are tetraploid (2n=4x=80) and only one specie is hexaploid (2n=6x=120). There are no significant variations in the distribution and position of heterochromatin within the genus. Most of the species posses heterochromatin blocks located ...

The interior of the neuronal cell nucleus is a highly organized three-dimensional (3D) structure where regions of the genome that are linearly millions of bases apart establish sub-structures with specialized functions. To investigate neuronal chromatin organization and dynamics in vivo, we generated bitransgenic mice expressing GFP-tagged histone H2B in principal neurons of the forebrain. Surprisingly, the expression of this chimeric histone in mature neurons caused chromocenter declustering and disrupted the association of heterochromatin with the nuclear lamina. The loss of these structures did not affect neuronal viability but was associated with specific transcriptional and behavioural deficits related to serotonergic dysfunction. Overall, our results demonstrate that the 3D organization of chromatin within neuronal cells provides an additional level of epigenetic regulation of gene expression that critically impacts neuronal function. This in turn suggests that some loci associated with ...

Cellular senescence is definitely an essential tumor suppression mechanism. PIK-93 exposed that BRG1h association with the human being and gene marketers was improved during senescence caused by oncogenic RAS or BRCA1 knockdown. Regularly, knockdown of pRB, g21CIP1, and g16INK4a, but not really g53, covered up SAHF development caused by BRG1. Collectively, these studies reveal the molecular underpinning by which BRG1 acts of BRCA1 to promote SAHF formation and senescence downstream. Intro Service of oncogenes (such as RAS) in major mammalian cells PIK-93 typically sets off mobile senescence, a condition of permanent cell development police arrest (1, 2). Oncogene-induced senescence can be an essential growth reductions system (1). Senescent cells display many molecular and morphological qualities. For example, they are positive for senescence-associated -galactosidase (SA-gal) activity (3). In addition, chromatin in the nuclei of senescent human being cells typically reorganizes to type ...

Mammalian interphase chromosomes interact with the nuclear lamina (NL) through hundreds of large lamina-associated domains (LADs). We report a method to map NL contacts genome-wide in single human cells. Analysis of nearly 400 maps reveals a core architecture consisting of gene-poor LADs that contact the NL with high cell-to-cell consistency, interspersed by LADs with more variable NL interactions. The variable contacts tend to be cell-type specific and are more sensitive to changes in genome ploidy than the consistent contacts. Single-cell maps indicate that NL contacts involve multivalent interactions over hundreds of kilobases. Moreover, we observe extensive intra-chromosomal coordination of NL contacts, even over tens of megabases. Such coordinated loci exhibit preferential interactions as detected by Hi-C. Finally, the consistency of NL contacts is inversely linked to gene activity in single cells and correlates positively with the heterochromatic histone modification H3K9me3. These results

The human population is getting ageing. Both ageing and age-related diseases are correlated with an increased number of senescent cells in the organism. Senescent cells do not divide but are metabolically active and influence their environment by secreting many proteins due to a phenomenon known as senescence associated secretory phenotype (SASP). Senescent cells differ from young cells by several features. They possess more damaged DNA, more impaired mitochondria and an increased level of free radicals that cause the oxidation of macromolecules. However, not only biochemical and structural changes are related to senescence. Senescent cells have an altered chromatin structure, and in consequence, altered gene expression. With age, the level of heterochromatin decreases, and less condensed chromatin is more prone to DNA damage. On the one hand, some gene promoters are easily available for the transcriptional machinery; on the other hand, some genes are more protected (locally increased level of ...

You will need to recognize lymphocytes in tissues.. You can find them nearly anywhere. Often they are simply standing watch.. Resting lymphocytes have scanty cytoplasm, since they are not really doing anything but remembering. Resting lymphocytes nuclei always have a preponderance of heterochromatin. It is always clumpy, separated by thin strips of euchromatin.. Plasma cells make antibodies. They have:. ...

Cell, Cell Division, Cell Proliferation, Cells, Fission Yeast, Germ Cell, Heterochromatin, Kinases, Oncogenesis, Regulation, Schizosaccharomyces, Schizosaccharomyces Pombe, Yeast

Plays an essential role in normal development and survival. Involved in regulation of the expansion or survival of lymphoid cells. Required for de novo or maintenance DNA methylation. May control silencing of the imprinted CDKN1C gene through DNA methylation. May play a role in formation and organization of heterochromatin, implying a functional role in the regulation of transcription and mitosis (By similarity ...

There is variability in the whole procedure depending largely on the strain from which the stem cells have been derived. Generally cells derived from strain 129 are used. This specific strain is not suitable for many experiments (e.g., behavioural), so it is very common to backcross the offspring to other strains. Some genomic loci have been proven very difficult to knock out. Reasons might be the presence of repetitive sequences, extensive DNA methylation, or heterochromatin. The confounding presence of neighbouring 129 genes on the knockout segment of genetic material has been dubbed the flanking-gene effect.[6] Methods and guidelines to deal with this problem have been proposed.[7][8]. Another limitation is that conventional (i.e. non-conditional) knockout mice develop in the absence of the gene being investigated. At times, loss of activity during development may mask the role of the gene in the adult state, especially if the gene is involved in numerous processes spanning development. ...

A Berkeley Lab team led by Dr. Gary Karpen, Adjunct Professor of Cell and Developmental Biology, uncovered evidence that heterochromatin organizes large parts of the genome into specific regions of the nucleus using liquid-liquid phase separation, a mechanism well-known in physics but whose importance for biology has only recently been revealed.. Read more.... ...

In another big edition of the GARNet Research Roundup we cover many different areas of research that utilise a varied group of experimental organisms!. The first paper from the Feng lab at the John Innes Centre performs an assessment of the factors influencing heterochromatin activity in sperm companion cells. Second is work from the JIC and Cardiff University that looks at the role of an auxin minima during fruit valve margin differentiation.. The next two papers have authors from Edinburgh. Firstly the McCormick lab has developed a stereo-based 3D imaging system for plants while Steven Spoel is a co-author on a study that looks at the pathogen responsive gene NPR1.. Coming from across the M8 is a paper from the Christie lab in Glasgow that looks into using phototropin genes as potential targets for crop improvement.. The next paper is from Oxford Brookes University where they visualise the movement of protein nanodomain clusters within the plasma membrane. Elsewhere in Oxford is a paper from ...

Gurgaon , officially Gurugram , is a city located in the northern Indian state of Haryana . It is situated near the Delhi - Haryana border, about 30 kilometres (19 mi) southwest of the national capital New Delhi and 268 km (167 mi) south of Chandigarh , the state capital. It is one of the major satellite cities of Delhi and is part of the National Capital Region of India . As of 2011 , Gurgaon .... Learn More ...

tin and ATM mediated DSB repair occurring in heterochromatic regions. ATM is both recruited by and essential for normal DSB repair by the MRN complex which, as

犬吠埼ホテルは、ゆるやかなカーブを描く地平線が美しい、太平洋を一望できるオーシャンビューが素敵なホテルです。犬吠埼温泉「湯元黒潮の湯」を抱え、内風呂・展望露天風呂だけでなく足湯や岩盤浴などもお楽しみ頂けます。また、この犬吠埼は本州最初の初日の出がご覧頂ける場所として有名で、当ホテルは小高い丘の上に佇んでおり、最高のロケーションと喜ばれております。