The mammalian endoplasmic reticulum stress response element consists of an evolutionarily conserved tripartite structure and interacts with a novel stress-inducible complex. (1/440)

When mammalian cells are subjected to calcium depletion stress or protein glycosylation block, the transcription of a family of glucose-regulated protein (GRP) genes encoding endoplasmic reticulum (ER) chaperones is induced to high levels. The consensus mammalian ER stress response element (ERSE) conserved among grp promoters consists of a tripartite structure CCAAT(N9)CCACG, with N being a strikingly GC-rich region of 9 bp. The ERSE, in duplicate copies, can confer full stress inducibility to a heterologous promoter in a sequence-specific but orientation-independent manner. In addition to CBF/NF-Y and YY1 binding to the CCAAT and CCACG motifs, respectively, we further discovered that an ER stress-inducible complex (ERSF) from HeLa nuclear extract binds specifically to the ERSE. Strikingly, the interaction of the ERSF with the ERSE requires a conserved GGC motif within the 9 bp region. Since mutation of the GGC triplet sequence also results in loss of stress inducibility, specific sequence within the 9 bp region is an integral part of the tripartite structure. Finally, correlation of factor binding with stress inducibility reveals that ERSF binding to the ERSE alone is not sufficient; full stress inducibility requires integrity of the CCAAT, GGC and CCACG sequence motifs, as well as precise spacing among these sites.  (+info)

Positive and negative regulatory elements in the upstream region of the rat Cu/Zn-superoxide dismutase gene. (2/440)

Cu/Zn-superoxide dismutase (SOD1) catalyses the dismutation of superoxide radicals and neutralizes the oxidative effects of various chemicals. Deletion analysis of the upstream region of the rat SOD1 gene revealed that the promoter contains a positive regulatory element (PRE) and a negative regulatory element (NRE), which encompass the regions from -576 to -412 and from -412 to -305 respectively from the site of initiation of transcription. These DNA elements showed enhancer and silencer activities respectively in the natural context and in a heterologous promoter system. Using an electrophoretic-mobility-shift assay and a supershift assay with a specific antibody, the cis-elements of the PRE and NRE were identified as binding sites for transcription factors Elk1 and YY1 (Ying-Yang 1) respectively. Consistent with the presumed roles of the PRE and NRE, Elk1 increased SOD1 gene transcription about 4-5-fold, whereas YY1 exerted a negative effect of about 6-fold. Mutations of the Elk1- and YY1-binding sites led to diminution and elevation respectively of transcriptional activities, both in the natural context and in heterologous promoter systems. These results suggest that the transcription factors Elk1 and YY1, binding in the PRE and NRE respectively, co-ordinate the expression of the SOD1 gene.  (+info)

Co-stimulation of promoter for low density lipoprotein receptor gene by sterol regulatory element-binding protein and Sp1 is specifically disrupted by the yin yang 1 protein. (3/440)

Sterol regulation of gene expression in mammalian cells is mediated by an interaction between the cholesterol-sensitive sterol regulatory element-binding proteins (SREBPs) and promoter-specific but generic co-regulatory transcription factors such as Sp1 and NF-Y/CBF. Thus, sterol-regulated promoters that require different co-regulatory factors could be regulated independently through targeting the specific interaction between the SREBPs and the individual co-regulatory proteins. In the present studies we demonstrate that transiently expressed yin yang 1 protein (YY1) inhibits the SREBP-mediated activation of the low density lipoprotein (LDL) receptor in a sensitive and dose-dependent manner. The inhibition is independent of YY1 binding directly to the LDL receptor promoter, and we show that the same region of YY1 that interacts in solution with Sp1 also interacts with SREBP. Furthermore, other SREBP-regulated genes that are not co-regulated by Sp1 are either not affected at all or are not as sensitive to the repression. Thus, the specific interaction that occurs between SREBPs and Sp1 to stimulate the LDL receptor promoter is a specific target for inhibition by the YY1 protein, and we provide evidence that the mechanism can be at least partially explained by the ability of YY1 to inhibit the interaction between SREBP and Sp1 in solution in vitro. The LDL receptor is the key gene of cholesterol uptake, and the rate-controlling genes of cholesterol synthesis are stimulated by the concerted action of SREBPs along with coregulators that are distinct from Sp1. Therefore, repression of gene expression through specifically targeting the interaction between SREBP and Sp1 would provide a molecular mechanism to explain how cholesterol uptake can be regulated independently from cholesterol biosynthesis in mammalian cells.  (+info)

USF/c-Myc enhances, while Yin-Yang 1 suppresses, the promoter activity of CXCR4, a coreceptor for HIV-1 entry. (4/440)

Transcription factors USF1 and USF2 up-regulate gene expression (i.e. , HIV-1 long terminal repeats) via interaction with an E box on their target promoters, which is also a binding site for c-Myc. The c-Myc oncoprotein is important in control of cellular proliferation and differentiation, while Yin-Yang 1 (YY1) has been shown to control the expression of a number of cellular and viral genes. These two proteins physically interact with each other and mutually inhibit their respective biological functions. In this study, we show that USF/c-Myc up-regulates, while YY1 down-regulates the promoter activity of CXCR4, a coreceptor for T cell-tropic HIV-1 entry. We have identified an E box around -260 and a YY1 binding site around -300 relative to the transcription start site. Mutation of the E box abolished USF/c-Myc-mediated up-regulation of CXCR4 promoter activity, and mutation of the YY1 binding site was associated with unresponsiveness to YY1-mediated inhibition. These data suggest that USF/c-Myc and YY1 may play an important role in the HIV-1-replicative cycle, by modulating both the viral fusion/entry process and viral expression.  (+info)

Analysis of linked human epsilon and gamma transgenes: effect of locus control region hypersensitive sites 2 and 3 or a distal YY1 mutation on stage-specific expression patterns. (5/440)

Stage-specific expression of the human beta-like globin genes is controlled by interactions between regulatory elements near the individual genes and additional elements located upstream in the Locus Control Region (LCR). Elucidation of the mechanisms that govern these interactions could suggest strategies to reactivate fetal (gamma) or embryonic (epsilon) genes in individuals with severe hemoglobinopathies. This study extends an earlier analysis of a transgenic construct, HS3epsilon gamma, testing: (A) the effect of substitution of HS2 for HS3 on stage-specific expression of the epsilon and gamma genes and, (B) the role of an evolutionarily conserved YY1 binding site in transcriptional regulation of the gamma gene. The data show that both HS3epsilon gamma and HS2epsilon gamma can individually support embryonic expression of epsilon and fetal expression of Agamma. Thus, the cis regulators of distinct expression patterns for epsilon and gamma are likely to reside near the genes, rather than in specific hypersensitive sites of the LCR. Alterations in Agamma expression patterns observed in transgenic lines carrying a construct with a mutation in a conserved YY1 binding site at -1086 indicate that this site might function to facilitate active transcription of the gamma gene in fetal life.  (+info)

YY1 is a negative regulator of transcription of three sterol regulatory element-binding protein-responsive genes. (6/440)

Ying Yang 1 (YY1) is shown to bind to the proximal promoters of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, farnesyl diphosphate (FPP) synthase, and the low density lipoprotein (LDL) receptor. To investigate the potential effect of YY1 on the expression of SREBP-responsive genes, HepG2 cells were transiently transfected with luciferase reporter constructs under the control of promoters derived from either HMG-CoA synthase, FPP synthase, or the LDL receptor genes. The luciferase activity of each construct increased when HepG2 cells were incubated in lipid-depleted media or when the cells were cotransfected with a plasmid encoding mature sterol regulatory element-binding protein (SREBP)-1a. In each case, the increase in luciferase activity was attenuated by coexpression of wild-type YY1 but not by coexpression of mutant YY1 proteins that are known to be defective in either DNA binding or in modulating transcription of other known YY1-responsive genes. In contrast, incubation of cells in lipid-depleted media resulted in induction of an HMG-CoA reductase promoter-luciferase construct by a process that was unaffected by coexpression of wild-type YY1. Electromobility shift assays were used to demonstrate that the proximal promoters of the HMG-CoA synthase, FPP synthase, and the LDL receptor contain YY1 binding sites and that YY1 displaced nuclear factor Y from the promoter of the HMG-CoA synthase gene. We conclude that YY1 inhibits the transcription of specific SREBP-dependent genes and that, in the case of the HMG-CoA synthase gene, this involves displacement of nuclear factor Y from the promoter. We hypothesize that YY1 plays a regulatory role in the transcriptional regulation of specific SREBP-responsive genes.  (+info)

Expression of the mouse pre-T cell receptor alpha gene is controlled by an upstream region containing a transcriptional enhancer. (7/440)

The pre-T cell receptor alpha (pTalpha) protein is a critical component of the pre-T cell receptor complex in early thymocytes. The expression of the pTalpha gene is one of the earliest markers of the T cell lineage and occurs exclusively in pre-T cells. To investigate the molecular basis of thymocyte-specific gene expression, we searched for the genomic elements regulating transcription of the mouse pTalpha gene. We now report that expression of the pTalpha gene is primarily controlled by an upstream genomic region, which can drive thymocyte-specific expression of a marker gene in transgenic mice. Within this region, we have identified two specific DNase-hypersensitive sites corresponding to a proximal promoter and an upstream transcriptional enhancer. The pTalpha enhancer appears to function preferentially in pre-T cell lines and binds multiple nuclear factors, including YY1. The enhancer also contains two G-rich stretches homologous to a critical region of the thymocyte-specific lck proximal promoter. Here we show that these sites bind a common nuclear factor and identify it as the zinc finger protein ZBP-89. Our data establish a novel experimental model for thymocyte-specific gene expression and suggest an important role for ZBP-89 in T cell development.  (+info)

RYBP, a new repressor protein that interacts with components of the mammalian Polycomb complex, and with the transcription factor YY1. (8/440)

The products of the Polycomb group (PcG) of genes are necessary for the maintenance of transcriptional repression of a number of important developmental genes, including the homeotic genes. A two-hybrid screen was used to search for putative new members of the PcG of genes in mammals. We have identified a new Zn finger protein, RYBP, which interacts directly with both Ring1 proteins (Ring1A and Ring1B) and with M33, two mutually interacting sets of proteins of the mammalian Polycomb complex. Ring1 binds RYBP and M33 through the same C-terminal domain, whereas the RYBP-M33 interaction takes place through an M33 domain not involved in Ring1 binding. RYBP also interacts directly with YY1, a transcription factor partially related to the product of the Drosophila pleiohomeotic gene. In addition, we show here that RYBP acts as a transcriptional repressor in transiently transfected cells. Finally, RYBP shows a dynamic expression pattern during embryogenesis which initially overlaps partially that of Ring1A in the central nervous system, and later becomes ubiquitous. Taken together, these data suggest that RYBP may play a relevant role in PcG function in mammals.  (+info)