Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binding sites for the dimeric transcription factor activator protein (AP)-1 are found in numerous immunoregulatory and inflammatory genes. The precise mechanisms by which AP-1 activates or represses immune response genes and in particular the roles of individual AP-1 subunits in inflammatory responses are largely unknown. We report here that c-Fos and Fos-related antigen-1 (Fra-1), two inducible components of AP-1, are recruited to the endogenous interleukin (IL)-8 promoter in an IL-1-dependent manner. c-Fos activates IL-8 transcription and synergizes in this effect with p65 NF-kappaB. In contrast, Fra-1 strongly inhibits inducible IL-8 transcription. Fra-1 activation involves its stabilization, ubiquitination, and interaction with histone deacetylase-1. Blockade of MEK1 by PD98059 suppresses c-Fos and Fra-1 expression and, thus, affects two counteractive signals for IL-8 mRNA synthesis simultaneously. This disturbs the inducible recruitment of TATA box-binding protein and RNA polymerase II to the IL-8 promoter. Additional experiments reveal that, in conjunction with p65 NF-kappaB, the MEK1-ERK-dependent synthesis of c-Fos and Fra-1 serves to adjust the overall expression level of IL-8 in response to two of its physiological inducers, IL-1 and epidermal growth factor. Relative to c-Fos, the delayed recruitment of Fra-1 to the IL-8 promoter provides an example how AP-1 subunits may dampen excessive chemokine synthesis.
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PMID:MEK1-dependent delayed expression of Fos-related antigen-1 counteracts c-Fos and p65 NF-kappaB-mediated interleukin-8 transcription in response to cytokines or growth factors. 1561 16

Expression of endothelial nitric-oxide synthase (eNOS) mRNA is highly restricted to the endothelial cell layer of medium to large sized arterial blood vessels. Here we assessed the chromatin environment of the eNOS gene in expressing and nonexpressing cell types. Within endothelial cells, but not a variety of nonendothelial cells, the nucleosomes that encompassed the eNOS core promoter and proximal downstream coding regions were highly enriched in acetylated histones H3 and H4 and methylated lysine 4 of histone H3. This differentially modified chromatin domain was selectively associated with functionally competent RNA polymerase II complexes. Endothelial cells were particularly enriched in acetylated histone H3 lysine 9, histone H4 lysine 12, and di- and tri-methylated lysine 4 of histone H3 at the core promoter. Histone modifications at this region, which we have previously demonstrated to exhibit cell-specific DNA methylation, were functionally relevant to eNOS expression. Inhibition of histone deacetylase activity by trichostatin A increased acetylation of histones H3 and H4 at the eNOS proximal promoter in nonexpressing cell types and led to increased steady-state eNOS mRNA transcript levels. H3 lysine 4 methylation was also essential for eNOS expression, since treatment of endothelial cells with methylthioadenosine, a known lysine 4 methylation inhibitor, decreased eNOS RNA levels, H3 lysine 4 methylation, and RNA polymerase II loading at the eNOS proximal promoter. Importantly, methylthioadenosine also prevented the trichostatin A-mediated increase in eNOS mRNA transcript levels in nonendothelial cells. Taken together, these findings provide strong evidence that the endothelial cell-specific expression of eNOS is controlled by cell-specific histone modifications.
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PMID:The expression of endothelial nitric-oxide synthase is controlled by a cell-specific histone code. 1587 70

In this study, the roles of Sp1/Sp3 transcription factors in the regulation of the activity of human telomerase reverse transcriptase (hTERT) promoter in response to ceramide were examined in the A549 human lung adenocarcinoma cells. The activity of the N-terminal truncated hTERT promoter, lacking the c-Myc recognition (E-box) region but containing multiple Sp1/Sp3 sites, was also significantly inhibited by C6-ceramide, indicating a role for ceramide in the regulation of Sp1/Sp3 function. Partial inhibition of Sp1 expression using small interfering RNA resulted in a significant inhibition of the hTERT promoter. Treatment with C6-ceramide inhibited the trans-activation function of overexpressed Sp1, whereas it induced the repressor effects of exogenous Sp3 on the hTERT promoter. The interaction between Sp1 and hTERT promoter DNA was significantly reduced in response to ceramide as assessed by chromatin immunoprecipitation analysis. In contrast, the promoter DNA-binding activity of Sp3 was slightly increased in response to C6-ceramide, resulting in the increased ratio of Sp3/Sp1 on the hTERT promoter, which was concomitant with the reduced recruitment of RNA polymerase II to the promoter. Furthermore, mutations of various Sp1/Sp3 recognition sequences significantly attenuated the activity of the promoter in the presence or absence of ceramide, demonstrating the importance of multiple Sp1/Sp3 recognition sites for the promoter activity. Mechanistically, the data demonstrated that C6-ceramide reduced the acetylation of Sp3 protein and partially blocked the activation of the hTERT promoter by the histone deacetylase inhibitor trichostatin A. The roles of endogenous long chain ceramide generated in response to gemcitabine in the inhibition of hTERT promoter activity and the regulation of Sp3 acetylation were also demonstrated.
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PMID:Sp1/Sp3-dependent regulation of human telomerase reverse transcriptase promoter activity by the bioactive sphingolipid ceramide. 1595 64

Although the current paradigm delegates histone deacetylases (HDACs) to the role of transcriptional co-repressors, we recently showed that HDAC activity was necessary for expression of the hematopoietic transcription factor PU.1. Chromatin immunoprecipitation analyses showed that inhibition of HDACs resulted in increased histone H4 acetylation within the promoter and intron 1 regions of the PU.1 locus. In contrast, increases in both H3 and H4 acetylation were seen for introns 2, 3 and 4 on the 3' end of the PU.1 locus. Maximal increases in histone H4 acetylation over the promoter and intron 1 region were seen within 10 min of HDAC inhibition, while the increases seen on the 3' end showed slower kinetics. The increases in H4 acetylation were reversible and decreased levels of acetylation correlated with re-expression of the PU.1 gene. Finally, we show that HDAC activity is required for association of RNA polymerase II with the PU.1 promoter.
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PMID:Histone H4 HDAC activity is necessary for expression of the PU.1 gene. 1613 4

Posttranslational modifications of histones play an essential role in heterochromatin assembly. Whereas the role of Clr4/Suv39h-mediated methylation of histone H3 at lysine 9 (H3K9) in heterochromatin assembly is well studied, the exact function of histone deacetylases (HDACs) in this process is unclear. We show that Clr3, a fission yeast homolog of mammalian class II HDACs, acts in a distinct pathway parallel to RNAi-directed heterochromatin nucleation to recruit Clr4 and mediate H3K9 methylation at the silent mating-type region and centromeres. At the mat locus, Clr3 is recruited at a specific site through a mechanism involving ATF/CREB family proteins. Once recruited, Clr3 spreads across the 20 kb silenced domain that requires its own HDAC activity and heterochromatin proteins including Swi6/HP1. We also demonstrate that Clr3 contributes to heterochromatin maintenance by stabilizing H3K9 trimethylation and by preventing histone modifications associated with active transcription, and that it limits RNA polymerase II accessibility to naturally silenced repeats at heterochromatin domains.
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PMID:The nucleation and maintenance of heterochromatin by a histone deacetylase in fission yeast. 1624 21

Interactions between the novel histone deacetylase inhibitor LAQ824 and the cyclin-dependent kinase inhibitor roscovitine were examined in human leukemia cells. Pretreatment (24 hours) with a subtoxic concentration of LAQ824 (30 nmol/L) followed by a minimally toxic concentration of roscovitine (10 micromol/L; 24 hours) resulted in greater than additive effects on apoptosis in U937, Jurkat, and HL-60 human leukemia cells and blasts from three patients with acute myelogenous leukemia. These events were associated with enhanced conformational changes in Bax; mitochondrial release of cytochrome c, Smac/DIABLO, and apoptosis-inducing factor; and a marked increase in caspase activation. LAQ824/roscovitine-treated cells displayed caspase-dependent down-regulation of p21(CIP1) and Mcl-1 and a pronounced caspase-independent reduction in X-linked inhibitor of apoptosis (XIAP) expression. The lethality of this regimen was significantly attenuated by ectopic expression of XIAP, a nuclear localization signal-defective p21(CIP1) mutant, Mcl-1, and Bcl-2. Combined exposure to LAQ824 and roscovitine resulted in a significant reduction in XIAP mRNA levels and diminished phosphorylation of the carboxyl-terminal domain of RNA polymerase II. Notably, roscovitine blocked LAQ824-mediated differentiation. Finally, LAQ824 and roscovitine individually and in combination triggered an increase in generation of reactive oxygen species; moreover, coadministration of the free radical scavenger N-acetylcysteine prevented LAQ824/roscovitine-mediated mitochondrial injury and apoptosis. Collectively, these findings suggest that combined treatment of human leukemia cells with LAQ824 and roscovitine disrupts maturation and synergistically induces apoptosis, lending further support for an antileukemic strategy combining novel histone deacetylase and cyclin-dependent kinase inhibitors.
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PMID:Potentiation of the lethality of the histone deacetylase inhibitor LAQ824 by the cyclin-dependent kinase inhibitor roscovitine in human leukemia cells. 1627 99

Yeast Rpd3 histone deacetylase plays an important role at actively transcribed genes. We characterized two distinct Rpd3 complexes, Rpd3L and Rpd3S, by MudPIT analysis. Both complexes shared a three subunit core and Rpd3L contains unique subunits consistent with being a promoter targeted corepressor. Rco1 and Eaf3 were subunits specific to Rpd3S. Mutants of RCO1 and EAF3 exhibited increased acetylation in the FLO8 and STE11 open reading frames (ORFs) and the appearance of aberrant transcripts initiating within the body of these ORFs. Mutants in the RNA polymerase II-associated SET2 histone methyltransferase also displayed these defects. Set2 functioned upstream of Rpd3S and the Eaf3 methyl-histone binding chromodomain was important for recruitment of Rpd3S and for deacetylation within the STE11 ORF. These data indicate that Pol II-associated Set2 methylates H3 providing a transcriptional memory which signals for deacetylation of ORFs by Rpd3S. This erases transcription elongation-associated acetylation to suppress intragenic transcription initiation.
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PMID:Histone H3 methylation by Set2 directs deacetylation of coding regions by Rpd3S to suppress spurious intragenic transcription. 1628 7

The yeast histone deacetylase Rpd3 can be recruited to promoters to repress transcription initiation. Biochemical, genetic, and gene-expression analyses show that Rpd3 exists in two distinct complexes. The smaller complex, Rpd3C(S), shares Sin3 and Ume1 with Rpd3C(L) but contains the unique subunits Rco1 and Eaf3. Rpd3C(S) mutants exhibit phenotypes remarkably similar to those of Set2, a histone methyltransferase associated with elongating RNA polymerase II. Chromatin immunoprecipitation and biochemical experiments indicate that the chromodomain of Eaf3 recruits Rpd3C(S) to nucleosomes methylated by Set2 on histone H3 lysine 36, leading to deacetylation of transcribed regions. This pathway apparently acts to negatively regulate transcription because deleting the genes for Set2 or Rpd3C(S) bypasses the requirement for the positive elongation factor Bur1/Bur2.
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PMID:Cotranscriptional set2 methylation of histone H3 lysine 36 recruits a repressive Rpd3 complex. 1628 8

Cells latently infected with HIV represent a currently insurmountable barrier to viral eradication in infected patients. Using the J-Lat human T-cell model of HIV latency, we have investigated the role of host factor binding to the kappaB enhancer elements of the HIV long terminal repeat (LTR) in the maintenance of viral latency. We show that NF-kappaB p50-HDAC1 complexes constitutively bind the latent HIV LTR and induce histone deacetylation and repressive changes in chromatin structure of the HIV LTR, changes that impair recruitment of RNA polymerase II and transcriptional initiation. Knockdown of p50 expression with specific small hairpin RNAs reduces HDAC1 binding to the latent HIV LTR and induces RNA polymerase II recruitment. Similarly, inhibition of histone deacetylase (HDAC) activity with trichostatin A promotes binding of RNA polymerase II to the latent HIV LTR. This bound polymerase complex, however, remains non-processive, generating only short viral transcripts. Synthesis of full-length viral transcripts can be rescued under these conditions by expression of Tat. The combination of HDAC inhibitors and Tat merits consideration as a new strategy for purging latent HIV proviruses from their cellular reservoirs.
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PMID:NF-kappaB p50 promotes HIV latency through HDAC recruitment and repression of transcriptional initiation. 1631 23

Eaf3, a component of the NuA4 histone acetylase and Rpd3 histone deacetylase complexes, is important for the global pattern of histone acetylation in Saccharomyces cerevisiae. Preferential deacetylation of coding regions requires the Eaf3 chromodomain and H3-K36 methylation by Set2. The Eaf3 chromodomain interacts with methylated H3-K36 peptides, suggesting that this interaction leads to preferential association and histone deacetylation of the 3' portions of coding regions by the Rpd3 complex. However, the Eaf3 chromodomain and H3-K36 methylation do not significantly affect acetylation at promoters, suggesting that Eaf3 has a distinct function, presumably in the NuA4 complex. Lastly, Eaf3 inhibits internal initiation within mRNA coding regions in a manner similar to FACT and Spt6. Our results link the pattern of preferential deacetylation at coding regions to the underlying patterns of H3-K36 methylation and phosphorylation of the RNA polymerase II C-terminal domain, and ultimately to the mechanism by which repressive chromatin structure is restored after transcriptional elongation.
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PMID:Eaf3 chromodomain interaction with methylated H3-K36 links histone deacetylation to Pol II elongation. 1636 21


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