scholarly journals Transcriptional Repression by XPc1, a New Polycomb Homolog in Xenopus laevis Embryos, Is Independent of Histone Deacetylase

1999 ◽  
Vol 19 (6) ◽  
pp. 3958-3968 ◽  
Author(s):  
John Strouboulis ◽  
Sashko Damjanovski ◽  
Danielle Vermaak ◽  
Funda Meric ◽  
Alan P. Wolffe
Keyword(s):  
Xenopus Laevis ◽  
Transcriptional Repression ◽  
Molecular Basis ◽  
Target Genes ◽  
Trichostatin A ◽  
Histone Deacetylation ◽  
Polycomb Group ◽  
Blastula Stage ◽  
Xenopus Laevis Embryos

ABSTRACT The Polycomb group (Pc-G) genes encode proteins that assemble into complexes implicated in the epigenetic maintenance of heritable patterns of expression of developmental genes, a function largely conserved from Drosophila to mammals and plants. The Pc-G is thought to act at the chromatin level to silence expression of target genes; however, little is known about the molecular basis of this repression. In keeping with the evidence that Pc-G homologs in higher vertebrates exist in related pairs, we report here the isolation of XPc1, a second Polycomb homolog in Xenopus laevis. We show that XPc1 message is maternally deposited in a translationally masked form in Xenopus oocytes, with XPc1 protein first appearing in embryonic nuclei shortly after the blastula stage. XPc1 acts as a transcriptional repressor in vivo when tethered to a promoter in Xenopus embryos. We find that XPc1-mediated repression can be only partially alleviated by an increase in transcription factor dosage and that inhibition of deacetylase activity by trichostatin A treatment has no effect on XPc1 repression, suggesting that histone deacetylation does not form the basis for Pc-G-mediated repression in our assay.

scholarly journals p53-Dependent Transcriptional Repression of c-myc Is Required for G1 Cell Cycle Arrest

2005 ◽  
Vol 25 (17) ◽  
pp. 7423-7431 ◽  
Author(s):  
Jenny S. L. Ho ◽  
Weili Ma ◽  
Daniel Y. L. Mao ◽  
Samuel Benchimol
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Histone Deacetylation ◽  
Dependent Manner ◽  
Cycle Arrest ◽  
Mouse Tissues

ABSTRACT The ability of p53 to promote apoptosis and cell cycle arrest is believed to be important for its tumor suppression function. Besides activating the expression of cell cycle arrest and proapoptotic genes, p53 also represses a number of genes. Previous studies have shown an association between p53 activation and down-regulation of c-myc expression. However, the mechanism and physiological significance of p53-mediated c-myc repression remain unclear. Here, we show that c-myc is repressed in a p53-dependent manner in various mouse and human cell lines and mouse tissues. Furthermore, c-myc repression is not dependent on the expression of p21WAF1. Abrogating the repression of c-myc by ectopic c-myc expression interferes with the ability of p53 to induce G1 cell cycle arrest and differentiation but enhances the ability of p53 to promote apoptosis. We propose that p53-dependent cell cycle arrest is dependent not only on the transactivation of cell cycle arrest genes but also on the transrepression of c-myc. Chromatin immunoprecipitation assays indicate that p53 is bound to the c-myc promoter in vivo. We report that trichostatin A, an inhibitor of histone deacetylases, abrogates the ability of p53 to repress c-myc transcription. We also show that p53-mediated transcriptional repression of c-myc is accompanied by a decrease in the level of acetylated histone H4 at the c-myc promoter and by recruitment of the corepressor mSin3a. These data suggest that p53 represses c-myc transcription through a mechanism that involves histone deacetylation.

scholarly journals The Growth Suppressor PML Represses Transcription by Functionally and Physically Interacting with Histone Deacetylases

2001 ◽  
Vol 21 (7) ◽  
pp. 2259-2268 ◽  
Author(s):  
Wen-Shu Wu ◽  
Sadeq Vallian ◽  
Edward Seto ◽  
Wen-Ming Yang ◽  
Diane Edmondson ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Cell Cycle Progression ◽  
Trichostatin A ◽  
Specific Inhibitor ◽  
Promyelocytic Leukemia ◽  
Histone Deacetylation ◽  
Growth Suppressor

ABSTRACT The growth suppressor promyelocytic leukemia protein (PML) is disrupted by the chromosomal translocation t(15;17) in acute promyelocytic leukemia (APL). PML plays a key role in multiple pathways of apoptosis and regulates cell cycle progression. The present study demonstrates that PML represses transcription by functionally and physically interacting with histone deacetylase (HDAC). Transcriptional repression mediated by PML can be inhibited by trichostatin A, a specific inhibitor of HDAC. PML coimmunoprecipitates a significant level of HDAC activity in several cell lines. PML is associated with HDAC in vivo and directly interacts with HDAC in vitro. The fusion protein PML-RARα encoded by the t(15;17) breakpoint interacts with HDAC poorly. PML interacts with all three isoforms of HDAC through specific domains, and its expression deacetylates histone H3 in vivo. Together, the results of our study show that PML modulates histone deacetylation and that loss of this function in APL alters chromatin remodeling and gene expression. This event may contribute to the development of leukemia.

scholarly journals The Human Candidate Tumor Suppressor Gene HIC1 Recruits CtBP through a Degenerate GLDLSKK Motif

2002 ◽  
Vol 22 (13) ◽  
pp. 4890-4901 ◽  
Author(s):  
Sophie Deltour ◽  
Sébastien Pinte ◽  
Cateline Guerardel ◽  
Bohdan Wasylyk ◽  
Dominique Leprince
Keyword(s):  
Binding Site ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Suppressor Gene ◽  
Close Relative ◽  
Consensus Binding Site ◽  
Candidate Tumor Suppressor Gene

ABSTRACT HIC1 (hypermethylated in cancer) and its close relative HRG22 (HIC1-related gene on chromosome 22) encode transcriptional repressors with five C2H2 zinc fingers and an N-terminal BTB/POZ autonomous transcriptional repression domain that is unable to recruit histone deacetylases (HDACs). Alignment of the HIC1 and HRG22 proteins from various species highlighted a perfectly conserved GLDLSKK/R motif highly related to the consensus CtBP interaction motif (PXDLSXK/R), except for the replacement of the virtually invariant proline by a glycine. HIC1 strongly interacts with mCtBP1 both in vivo and in vitro through this conserved GLDLSKK motif, thus extending the CtBP consensus binding site. The BTB/POZ domain does not interact with mCtBP1, but the dimerization of HIC1 through this domain is required for the interaction with mCtBP1. When tethered to DNA by fusion with the Gal4 DNA-binding domain, the HIC1 central region represses transcription through interactions with CtBP in a trichostatin A-sensitive manner. In conclusion, our results demonstrate that HIC1 mediates transcriptional repression by both HDAC-independent and HDAC-dependent mechanisms and show that CtBP is a HIC1 corepressor that is recruited via a variant binding site.

scholarly journals Postfertilization deadenylation of mRNAs in Xenopus laevis embryos is sufficient to cause their degradation at the blastula stage.

1997 ◽  
Vol 17 (1) ◽  
pp. 209-218 ◽  
Author(s):  
Y Audic ◽  
F Omilli ◽  
H B Osborne
Keyword(s):  
Xenopus Laevis ◽  
Untranslated Region ◽  
Sequence Information ◽  
Blastula Stage ◽  
Cytoplasmic Polyadenylation ◽  
Cis Acting ◽  
Stage Of Development ◽  
Chimeric Rnas ◽  
Xenopus Laevis Embryos

Although the maternal Xenopus laevis Eg mRNAs are deadenylated after fertilization, they are not immediately degraded and they persist in the embryos as poly(A)- transcripts. The degradation of these RNAs is not detected until the blastula stage of development (6 to 7 h postfertilization). To understand the basis for this delay between deadenylation and degradation, it is necessary to identify the cis-acting element(s) required to trigger degradation in blastula stage embryos. To this end, several chimeric RNAs containing different portions of the 3' untranslated region of Eg2 mRNA were injected into two-cell X. laevis embryos. We observed that only the RNAs that contained the cis-acting elements that confer rapid deadenylation were subsequently degraded at the blastula stage. This suggested that deadenylation may be sufficient to trigger degradation. By injecting chimeric RNAs devoid of Eg sequence information, we further showed that only deadenylated RNAs were degraded in X. laevis embryos. Last, introduction of a functional cytoplasmic polyadenylation element into a poly(A)- RNA, thereby causing its polyadenylation after injection into embryos, protected the RNA from degradation. Hence, in X. laevis embryos, the postfertilization deadenylation of maternal Eg mRNAs is sufficient to cause the degradation of an mRNA, which, however, only becomes apparent at the blastula stage. Possible causes for this delay between deadenylation and degradation are discussed in the light of these results.

FOG-1 Directly Binds to a Chromatin Remodeling and Deacetylase-Containing Complex To Mediate Transcriptional Repression by GATA-1.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 355-355
Author(s):  
Wei Hong ◽  
Minako Nakazawa ◽  
Ying-Yu Chen ◽  
Rajashree Kori ◽  
Carrie Rakowski ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Histone Deacetylation ◽  
Gene Repression ◽  
Single Point Mutation ◽  
Mutant Form ◽  
Erythroid Cells ◽  
Binding Studies ◽  
Nucleosome Remodeling ◽  
N Terminus

Abstract Terminal erythroid maturation requires coordinated activation of erythroid marker genes and repression of genes associated with the undifferentiated state. These gene expression patterns are mediated by the concerted action of the erythroid transcription factor GATA-1 and its cofactor FOG-1 that can activate or repress transcription depending on promoter context. We and others showed previously that one mechanism by which FOG-1 functions is to facilitate GATA-1 association with certain DNA target sites in vivo. Using gene complementation studies of GATA-1-ablated erythroid cells, we show that at several GATA-1-repressed target genes (c-kit, c-myc and GATA-2) FOG-1 is dispensable for GATA-1 occupancy in vivo but essential for gene repression and histone deacetylation. To examine how FOG-1 functions as co-repressor we performed affinity chromatography, conventional protein purification and in vitro binding studies to identify proteins that bind FOG-1. We discovered that FOG-1 directly associates with the nucleosome remodeling and histone deacetylase complex NURD. This interaction is mediated by a small conserved domain at the N-terminus of FOG-1 and the MTA-1 subunit of NURD. Association of FOG-1 with NURD occurs in vivo and depends on an intact N-terminus of FOG-1. A series of point mutations across the N-terminus of FOG-1 revealed a tight correlation between NURD binding and transcriptional repression. In particular, a single point mutation at the N-terminus of FOG-1 that abrogated NURD binding also blocked gene repression by FOG-1. Finally, the ability of GATA-1 to repress transcription was impaired in erythroid cells expressing a mutant form of FOG-1 that is defective for NURD binding. Together, these studies show that FOG-1 and very likely other FOG proteins are bona fide co-repressors that link GATA proteins to histone deacetylation and nucleosome remodeling via a novel protein interaction module.

scholarly journals Retinoblastoma Protein Disrupts Interactions Required for RNA Polymerase III Transcription

2000 ◽  
Vol 20 (24) ◽  
pp. 9192-9202 ◽  
Author(s):  
Josephine E. Sutcliffe ◽  
Timothy R. P. Brown ◽  
Simon J. Allison ◽  
Pamela H. Scott ◽  
Robert J. White
Keyword(s):  
Rna Polymerase ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Rna Polymerase Iii ◽  
Retinoblastoma Protein ◽  
Class Iii ◽  
Negative Effect ◽  
Pol Iii

ABSTRACT The retinoblastoma protein (RB) has been shown to suppress RNA polymerase (Pol) III transcription in vivo (R. J. White, D. Trouche, K. Martin, S. P. Jackson, and T. Kouzarides, Nature 382:88–90, 1996). This regulation involves interaction with TFIIIB, a multisubunit factor that is required for the expression of all Pol III templates (C. G. C. Larminie, C. A. Cairns, R. Mital, K. Martin, T. Kouzarides, S. P. Jackson, and R. J. White, EMBO J. 16:2061–2071, 1997; W.-M. Chu, Z. Wang, R. G. Roeder, and C. W. Schmid, J. Biol. Chem. 272:14755–14761, 1997). However, it has not been established why RB binding to TFIIIB results in transcriptional repression. For several Pol II-transcribed genes, RB has been shown to inhibit expression by recruiting histone deacetylases, which are thought to decrease promoter accessibility. We present evidence that histone deacetylases exert a negative effect on Pol III activity in vivo. However, RB remains able to regulate Pol III transcription in the presence of the histone deacetylase inhibitor trichostatin A. Instead, RB represses by disrupting interactions between TFIIIB and other components of the basal Pol III transcription apparatus. Recruitment of TFIIIB to most class III genes requires its binding to TFIIIC2, but this can be blocked by RB. In addition, RB disrupts the interaction between TFIIIB and Pol III that is essential for transcription. The ability of RB to inhibit these key interactions can explain its action as a potent repressor of class III gene expression.

scholarly journals Histone H2AK119 Mono-Ubiquitination is Essential for Polycomb-Mediated Transcriptional Repression

2019 ◽  
Author(s):  
Simone Tamburri ◽  
Elisa Lavarone ◽  
Daniel Fernández-Pérez ◽  
Marika Zanotti ◽  
Daria Manganaro ◽  
...  
Keyword(s):  
Cross Talk ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Human Tumors ◽  
Polycomb Group ◽  
Polycomb Group Proteins ◽  
Major Function ◽  
Cellular Identity

ABSTRACTThe major function of Polycomb group proteins (PcG) is to maintain transcriptional repression to preserve cellular identity. This is exerted by two distinct repressive complexes, PRC1 and PRC2, that modify histones by depositing H2AK119ub1 and H3K27me3, respectively. Both complexes are essential for development and are deregulated in several types of human tumors. PRC1 and PRC2 exist in different variants and show a complex regulatory cross-talk. However, the contribution that H2AK119ub1 plays in mediating PcG repressive functions remains largely controversial. Coupling an inducible system with the expression of a fully catalytic inactive RING1B mutant, we demonstrated that H2AK119ub1 deposition is essential to maintain PcG-target genes repressed in ESC. Loss of H2AK119ub1 induced a rapid displacement of PRC2 activity and a loss of H3K27me3 deposition. This affected both PRC2.1 and PRC2.2 variants and further correlated with a strong displacement and destabilization of canonical PRC1. Finally, we find that variant PRC1 forms can sense H2AK119ub1 deposition, which contributes to their stabilization specifically at sites where this modification is highly enriched. Overall our data place H2AK119ub1 deposition as central hub that mount PcG repressive machineries to preserve cell transcriptional identity.

scholarly journals Polycomb-group recruitment to a Drosophila target gene is the default state that is inhibited by a transcriptional activator

2021 ◽  
Vol 7 (29) ◽  
pp. eabg1556
Author(s):  
Elnaz Ghotbi ◽  
Piao Ye ◽  
Taylor Ervin ◽  
Anni Kum ◽  
Judith Benes ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Target Gene ◽  
Target Genes ◽  
De Novo ◽  
Polycomb Group ◽  
Polycomb Repressive Complex 2 ◽  
Repressive Chromatin ◽  
Group Recruitment ◽  
Default State ◽  
Present Experimental Evidence

Polycomb-group (PcG) proteins are epigenetic regulators that maintain the transcriptional repression of target genes following their initial repression by transcription factors. PcG target genes are repressed in some cells, but active in others. Therefore, a mechanism must exist by which PcG proteins distinguish between the repressed and active states and only assemble repressive chromatin environments at target genes that are repressed. Here, we present experimental evidence that the repressed state of a Drosophila PcG target gene, giant (gt), is not identified by the presence of a repressor. Rather, de novo establishment of PcG-mediated silencing at gt is the default state that is prevented by the presence of an activator or coactivator, which may inhibit the catalytic activity of Polycomb-repressive complex 2 (PRC2).

scholarly journals Differential Contributions of DNA-Binding Proteins to Polycomb Response Element Activity at the Drosophila giant Gene

Genetics ◽  
2020 ◽  
Vol 214 (3) ◽  
pp. 623-634
Author(s):  
Elnaz Ghotbi ◽  
Kristina Lackey ◽  
Vicki Wong ◽  
Katie T. Thompson ◽  
Evan G. Caston ◽  
...  
Keyword(s):  
Dna Binding ◽  
Dna Sequences ◽  
Transcriptional Repression ◽  
Binding Proteins ◽  
Target Genes ◽  
Dna Binding Proteins ◽  
Polycomb Group ◽  
Link Type ◽  
Element Activity

Polycomb-group (PcG) proteins are evolutionarily conserved epigenetic regulators whose primary function is to maintain the transcriptional repression of target genes. Recruitment of Drosophila melanogaster PcG proteins to target genes requires the presence of one or more Polycomb Response Elements (PREs). The functions or necessity for more than one PRE at a gene are not clear and individual PREs at some loci may have distinct regulatory roles. Various combinations of sequence-specific DNA-binding proteins are present at a given PRE, but only Pleiohomeotic (Pho) is present at all strong PREs. The giant (gt) locus has two PREs, a proximal PRE1 and a distal PRE2. During early embryonic development, Pho binds to PRE1 ∼30-min prior to stable binding to PRE2. This observation indicated a possible dependence of PRE2 on PRE1 for PcG recruitment; however, we find here that PRE2 recruits PcG proteins and maintains transcriptional repression independently of Pho binding to PRE1. Pho-like (Phol) is partially redundant with Pho during larval development and binds to the same DNA sequences in vitro. Although binding of Pho to PRE1 is dependent on the presence of consensus Pho-Phol-binding sites, Phol binding is less so and appears to play a minimal role in recruiting other PcG proteins to gt. Another PRE-binding protein, Sp1/Kruppel-like factor, is dependent on the presence of Pho for PRE1 binding. Further, we show that, in addition to silencing gene expression, PcG proteins dampen transcription of an active gene.

Physical and Functional Association of PLZF with Histone Methyl Transferase and Histone Demethylase.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 731-731
Author(s):  
Itsaso Hormaeche ◽  
Kim Rice ◽  
Joti Marango ◽  
Fabien Guidez ◽  
Arthur Zelent ◽  
...  
Keyword(s):  
Histone Methylation ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Histone H3 ◽  
Promyelocytic Leukemia ◽  
Gene Repression ◽  
Histone Demethylases ◽  
Methyl Transferase ◽  
Histone Methyl Transferase

Abstract The promyelocytic leukemia zinc finger protein (PLZF) is a transcription factor fused to RARα in the t(11;17) translocation associated with retinoic acid resistant acute promyelocytic leukemia (APL). As a result of this chromosomal abnormality, two oncogenic proteins are produced, PLZF-RARα and RARα-PLZF. Wild type PLZF is expressed in CD34+ progenitor cells and declines during differentiation. PLZF is a tumor suppressor that causes cell cycle arrest, downregulating genes such as cyclinA2 and c-myc. We previously showed that transcriptional repression by PLZF is mediated by the recruitment of histone deacetylases to target genes, this being critical for its ability to control growth and affect RAR target genes. We now show that PLZF alters the methylation state of histones in its target genes. A biotinylated form of PLZF co-purified in cells along with a histone methyl transferase (HMT) activity for native histones. Using mutant histone H3 tail peptides, we showed that this activity methylated histone H3 on lysine 9 (H3K9me). Tagged forms of PLZF as well as endogenous PLZF co-precipitated in vivo with G9a histone methyl transferase, an enzyme that can mono and dimethylate H3K9 in euchromatin subject to gene repression. The interaction of PLZF with G9a required the presence of the N-terminal BTB/POZ domain as well as a second, more C-terminal, repression domain of PLZF. Given the newly found role of active histone demethylation in gene control we also tested the interaction of PLZF with LSD1, an enzyme associated with gene repression that demethylates H3K4. As in the case of G9a, the interaction of PLZF with LSD1 required both repression domains, suggesting, that these proteins may be part of a multi-protein complex containing multiple contact points with PLZF. Expression of G9a or LSD1 augmented transcriptional repression mediated by PLZF on reporter genes, indicating a functional interaction between histone methylation modifiers and PLZF. To determine the ability of PLZF to affect chromatin methylation in vivo, a Gal4-PLZF fusion protein was expressed in cells containing a chromatin-embedded Gal4-tk-Luciferase reporter gene. In the presence of PLZF, a chromatin immunoprecipitation experiment showed an increase in H3K9 methylation of the target gene while H3K4 methylation decreased, consistent with the ability of PLZF to interact with LSD1 and G9a. Lastly we compared the ability of the histone modifying proteins to interact with the APL fusion proteins PLZF-RARα, PML-RARα and NPM-RARα. Co-precipitation experiments showed a robust interaction between PLZF-RARα and G9a and LSD1 while the PML-RARα and NPM-RARα fusions bound these proteins significantly less avidly. Collectively all these data indicate that specific histone methylation is an important mode of action of PLZF in gene repression. The retinoic acid resistance of t(11;17)-APL may be related to its ability to interact with HMTs and histone demethylases. Hence therapeutic targeting of HMTs and histone demethylases might be considered as a novel mode of therapy in APL and other hematological malignancies.

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