Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Monoclonal antibody 104 recognizes a subset of amphibian nuclear granules (B-snurposomes) and active sites of RNA polymerase II transcription in vertebrates and invertebrates. Monoclonal antibody 104 reacts with a set of nuclear serine- and arginine-rich phosphoproteins (SR family) with strikingly conserved apparent molecular masses. The most abundant family members in human (SRp33) and Drosophila (SRp55) cell lines can replace one another as essential splicing factors in a human cell-free system. Each of these polypeptides can functionally replace human SF2, an essential splicing factor that also regulates 5' splice site selection of alternatively spliced pre-mRNAs in vitro. Drosophila SRp55 also functions as an alternative splicing factor in the human cell-free system. Analysis of cloned cDNAs shows that SRp55 and SF2 are highly related and reveals regions of similarity to genetically defined regulators of alternative splicing in Drosophila. These results suggest that the conserved SR family of phosphoproteins, which includes SRp55 and SF2, is involved in constitutive pre-mRNA splicing and in the specificity of alternative splice site selection.
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PMID:Two members of a conserved family of nuclear phosphoproteins are involved in pre-mRNA splicing. 174 84

Human immunodeficiency virus type 1 (HIV-1) Tat interacts with cyclin T1 (CycT1), a regulatory partner of CDK9 in the positive transcription elongation factor (P-TEFb) complex, and binds cooperatively with CycT1 to TAR RNA to recruit P-TEFb and promote transcription elongation. We show here that Tat also stimulates phosphorylation of affinity-purified core RNA polymerase II and glutathione S-transferase-C-terminal-domain substrates by CycT1-CDK9, but not CycH-CDK7, in vitro. Interestingly, incubation of recombinant Tat-P-TEFb complexes with ATP enhanced binding to TAR RNA dramatically, and the C-terminal half of CycT1 masked binding of Tat to TAR RNA in the absence of ATP. ATP incubation lead to autophosphorylation of CDK9 at multiple C-terminal Ser and Thr residues, and full-length CycT1 (amino acids 728) [CycT1(1-728)], but not truncated CycT1(1-303), was also phosphorylated by CDK9. P-TEFb complexes containing a catalytically inactive CDK9 mutant (D167N) bound TAR RNA weakly and independently of ATP, as did a C-terminal truncated CDK9 mutant that was catalytically active but unable to undergo autophosphorylation. Analysis of different Tat proteins revealed that the 101-amino-acid SF2 HIV-1 Tat was unable to bind TAR with CycT1(1-303) in the absence of phosphorylated CDK9, whereas unphosphorylated CDK9 strongly blocked binding of HIV-2 Tat to TAR RNA in a manner that was reversed upon autophosphorylation. Replacement of CDK9 phosphorylation sites with negatively charged residues restored binding of CycT1(1-303)-D167N-Tat, and rendered D167N a more potent inhibitor of transcription in vitro. Taken together, these results demonstrate that CDK9 phosphorylation is required for high-affinity binding of Tat-P-TEFb to TAR RNA and that the state of P-TEFb phosphorylation may regulate Tat transactivation in vivo.
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PMID:CDK9 autophosphorylation regulates high-affinity binding of the human immunodeficiency virus type 1 tat-P-TEFb complex to TAR RNA. 1095 91

We have tested for combined anti-HIV-1 effects of a hammerhead ribozyme and antiretroviral drugs and the possibility of reducing the drug burden of patients on highly active antiretroviral therapy (HAART). The antiretroviral compounds used represent the three groups in HAART: nucleoside analogue reverse-transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, and protease inhibitors. A human T cell line (HUT78), stably expressing a hammerhead ribozyme targeted to nef (hhRz.nef(9016-9029)), was infected with HIV-1(SF2) in the presence of a single drug. The combined effects on HIV-1 replication were measured by p24 antigen determinations over a 2-week period. In the presence of the ribozyme, smaller amounts of antiretroviral drugs were required to reduce the HIV-1 p24 levels equally as much as when only drugs were present. The results support a strategy of combining ribozyme gene therapy with HAART to improve the long-term outcome of anti-HIV-1 therapy.
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PMID:Smaller amounts of antiretroviral drugs are needed when combined with an active ribozyme against HIV-1. 1131 14

Here we investigate the promoter control of alternative splicing by studying two transcriptional activators on templates under replicating conditions. SV40 large T-antigen (T-Ag) activates template replication only 2-fold but transcription 25-fold. T-Ag-mediated replication, reported to inhibit RNA polymerase II elongation, provokes a 10- to 30-fold increase in the inclusion of the fibronectin EDI exon into mature mRNA. The T-Ag effect is exon specific, occurs in cis and depends strictly on DNA replication and not on cell transformation. VP16, an activator of transcriptional initiation and elongation, has a similar effect on transcription but the opposite effect on splicing: EDI inclusion is inhibited by 35-fold. VP16 completely reverts the T-Ag effect, but a VP16 mutant with reduced elongation ability provokes only partial reversion. Both T-Ag and VP16 promote conspicuous co-localization of mRNA with nuclear speckles that contain the SR protein SF2/ASF, a positive regulator of EDI inclusion. Therefore, we conclude that co-localization of transcripts and speckles is not sufficient to stimulate EDI inclusion.
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PMID:Antagonistic effects of T-Ag and VP16 reveal a role for RNA pol II elongation on alternative splicing. 1159 18

Promoters and enhancers are cis-acting elements that control gene transcription via complex networks of protein-DNA and protein-protein interactions. Whereas promoters deal with putting in place the RNA polymerase, both enhancers and promoters can control transcriptional initiation and elongation. We have previously shown that promoter structure modulates alternative splicing, strengthening the concept of a physical and functional coupling between transcription and splicing. Here we report that the promoter effect is due to the control of RNA pol II elongation. We found that the simian virus 40 (SV40) transcriptional enhancer, inserted in fibronectin (FN) minigene constructs transfected into mammalian cells, controls alternative splicing by inhibiting inclusion of the FN extra domain I (EDI) exon into mature mRNA. Deletion analysis of enhancer subdomains and competitions in vivo with excess of specific enhancer DNA subfragments demonstrate that the "minimal" enhancer, consisting of two 72-bp repeats, is responsible for the splicing effect. The 72-bp repeat region has been reported to promote RNA pol II elongation. When transcription is driven by the alpha-globin promoter linked to the SV40 enhancer, basal EDI inclusion and activation by the SR (Ser-Arg-rich) protein SF2/ASF are much lower than with other promoters. Deletion of only one of the two 72-bp repeats not only provokes higher EDI inclusion levels but allows responsiveness to SF2/ASF. These effects are the consequence of a decrease in RNA pol II elongation evidenced both by an increase in the proportions of shorter proximal over full length transcripts and by higher pol II densities upstream of the alternative exon detected by chromatin immunoprecipitation.
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PMID:Regulation of alternative splicing by a transcriptional enhancer through RNA pol II elongation. 1206 Jul 63

Using hybrid minigene experiments, we have investigated the role of the promoter architecture on the regulation of two alternative spliced exons, cystic fibrosis transmembrane regulator (CFTR) exon 9 and fibronectin extra domain-A (EDB). A specific alternative splicing pattern corresponded to each analyzed promoter. Promoter-dependent sensitivity to cotransfected regulatory splicing factor SF2/ASF was observed only for the CFTR exon 9, whereas that of the EDB was refractory to promoter-mediated regulation. Deletion in the CFTR minigene of the downstream intronic splicing silencer element binding SF2/ASF abolished the specific promoter-mediated response to this splicing factor. A systematic analysis of the regulatory cis-acting elements showed that in the presence of suboptimal splice sites or by deletion of exonic enhancer elements the promoter-dependent sensitivity to splicing factor-mediated inhibition was lost. However, the basal regulatory effect of each promoter was preserved. The complex relationships between the promoter-dependent sensitivity to SF2 modulated by the exon 9 definition suggest a kinetic model of promoter-dependent alternative splicing regulation that possibly involves differential RNA polymerase II elongation.
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PMID:Promoter architecture modulates CFTR exon 9 skipping. 1242 14

Transcription and pre-mRNA splicing are coordinated temporally and spatially, and both processes can influence each other. In particular, control of transcriptional elongation by RNA polymerase II has proved to be important for alternative splicing regulation. In this report we demonstrate that the efficiency of exon recognition by the splicing machinery is crucial for the elongation control. Alternative splicing of the fibronectin extra domain I (EDI) is because the polypyrimidine tract of its 3'-splice site occurs suboptimal. By mutating the polypyrimidine tract of EDI in two different positions, individually or in combination, and by disrupting its exonic splicing silencer, we managed to generate minigenes with increasing degrees of exon recognition. Improvement of exon recognition is evidenced by independence from the splicing regulator SF2/ASF for inclusion. The mutated minigenes were used to transfect human cells in culture and study the responsiveness of EDI alternative splicing to activation or inhibition of pol II elongation. Our results revealed that responsiveness of exon skipping to elongation is inversely proportional to 3'-splice site strength, which means that the better the alternative exon is recognized by the splicing machinery, the less its degree of inclusion is affected by transcriptional elongation.
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PMID:Influence of polymerase II processivity on alternative splicing depends on splice site strength. 1453 Feb 56

Exposure of cells to stressful conditions results in the rapid synthesis of a subset of specialized proteins termed heat shock proteins (HSPs) which function in protecting the cell against damage. The stress-induced activation of hsp genes is controlled by the heat shock transcription factor 1 (HSF1). At the cellular level, one of the most striking effects of stress is the rapid and reversible redistribution of HSF1 into a few nuclear structures termed nuclear stress granules which form primarily on the 9q12 locus in humans. Within these structures, HSF1 binds to satellite III repeated elements and drives the RNA polymerase II-dependent transcription of these sequences into stable RNAs which remain associated with the 9q12 locus for a certain time after synthesis. Other proteins, in particular splicing factors, were also shown to relocalize to the granules upon stress. Here, we investigated the role of stress-induced satellite III transcripts in the relocalization of splicing factors to the granules. We show that the recruitment of the two serine/arginine-rich (SR) proteins SF2/ASF and SRp30c requires the presence of stress-induced satellite III transcripts. In agreement with these findings, we identified the second RNA-recognition motif (RRM2) of hSF2/ASF as the motif required for the targeting to the granules, and we showed by immunoprecipitation that the endogenous hSF2/ASF protein is present in a complex with satellite III transcripts in stressed cells in vivo. Interestingly, satellite III transcripts also immunoprecipitate together with small nuclear ribonucleoproteins (snRNPs) in vivo whereas the intronless hsp70 transcripts do not, supporting the proposal that these transcripts are subject to splicing. Altogether, these data highlight the central role for satellite III transcripts in the targeting and/or retention of splicing factors into the granules upon stress.
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PMID:A key role for stress-induced satellite III transcripts in the relocalization of splicing factors into nuclear stress granules. 1533 64

Coupling of transcription and DNA repair in bacteria is mediated by transcription-repair coupling factor (TRCF, the product of the mfd gene), which removes transcription elongation complexes stalled at DNA lesions and recruits the nucleotide excision repair machinery to the site. Here we describe the 3.2 A-resolution X-ray crystal structure of Escherichia coli TRCF. The structure consists of a compact arrangement of eight domains, including a translocation module similar to the SF2 ATPase RecG, and a region of structural similarity to UvrB. Biochemical and genetic experiments establish that another domain with structural similarity to the Tudor-like domain of the transcription elongation factor NusG plays a critical role in TRCF/RNA polymerase interactions. Comparison with the translocation module of RecG as well as other structural features indicate that TRCF function involves large-scale conformational changes. These data, along with a structural model for the interaction of TRCF with the transcription elongation complex, provide mechanistic insights into TRCF function.
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PMID:Structural basis for bacterial transcription-coupled DNA repair. 1646 98

Transcription-repair coupling factors (TRCFs) are SF2 ATPases that couple transcription to DNA-damage repair by recognizing and removing RNA polymerase-elongation complexes stalled at DNA lesions and recruiting the nucleotide excision-repair machinery to the damaged sites. As a first step towards understanding the TRCF mechanism, the 130 kDa Escherichia coli TRCF (the product of the mfd gene) has been overexpressed, purified and crystallized using an unusual precipitant, pentaerythritol ethoxylate. Initial phases were obtained using single-wavelength anomalous dispersion with a highly redundant 4 A resolution data set collected from selenomethionyl-substituted crystals and dramatically improved by density modification and phase extension to 3.2 A resolution. Model building and refinement, which are in progress, will provide insight into transcription-coupled DNA-repair pathways, as this represents the first TRCF to be crystallized to date.
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PMID:Crystallization and preliminary structure determination of Escherichia coli Mfd, the transcription-repair coupling factor. 1651 Dec 35


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