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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RNA polymerase III (Pol III) transcription is subject to repression by the retinoblastoma protein RB, both in vitro and in vivo (R. J. White, D. Trouche, K. Martin, S. P. Jackson, and T. Kouzarides, Nature 382:88-90, 1996). This is achieved through a direct interaction between RB and 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). p107 and p130 are two closely related proteins that display 30 to 35% identity with the RB polypeptide and share some of its functions. We show that p107 and p130 can both repress Pol III transcription in transient transfection assays or when added to cell extracts. Pull-down assays and immunoprecipitations using recombinant components demonstrate that a subunit of TFIIIB interacts physically with p107 and p130. In addition, endogenous TFIIIB is shown by cofractionation and coimmunoprecipitation to associate stably with both p107 and p130. Disruption of this interaction in vivo by using the E7 oncoprotein of human papillomavirus results in a marked increase in Pol III transcription. Pol III activity is also deregulated in fibroblasts derived from p107 p130 double knockout mice. We conclude that TFIIIB is targeted for repression not only by RB but also by its relatives p107 and p130.
Mol Cell Biol 1999 Jun
PMID:RNA polymerase III transcription factor IIIB is a target for repression by pocket proteins p107 and p130. 1033 Jan 66

Formation of mRNA 3' ends in eukaryotes requires the interaction of transacting factors with cis-acting signal elements on the RNA precursor by two distinct mechanisms, one for the cleavage of most replication-dependent histone transcripts and the other for cleavage and polyadenylation of the majority of eukaryotic mRNAs. Most of the basic factors have now been identified, as well as some of the key protein-protein and RNA-protein interactions. This processing can be regulated by changing the levels or activity of basic factors or by using activators and repressors, many of which are components of the splicing machinery. These regulatory mechanisms act during differentiation, progression through the cell cycle, or viral infections. Recent findings suggest that the association of cleavage/polyadenylation factors with the transcriptional complex via the carboxyl-terminal domain of the RNA polymerase II (Pol II) large subunit is the means by which the cell restricts polyadenylation to Pol II transcripts. The processing of 3' ends is also important for transcription termination downstream of cleavage sites and for assembly of an export-competent mRNA. The progress of the last few years points to a remarkable coordination and cooperativity in the steps leading to the appearance of translatable mRNA in the cytoplasm.
Microbiol Mol Biol Rev 1999 Jun
PMID:Formation of mRNA 3' ends in eukaryotes: mechanism, regulation, and interrelationships with other steps in mRNA synthesis. 1035 56

We have developed a coupled in vitro transcription-polyadenylation system to investigate RNA polymerase II (Pol II) termination, which depends on active polyadenylation of the nascent RNA. Specific G-rich sequences originally identified as binding sites for the transcription factor MAZ both pause Pol II and activate polyadenylation of an upstream poly(A) signal. They do not affect polyadenylation efficiency in an uncoupled cleavage assay. In contrast, pausing of Pol II elongation induced by a high-affinity DNA-binding protein does not activate polyadenylation, indicating that G-rich MAZ sequences have a specific effect on polyadenylation. They also promote intrinsic pausing of purified Pol II, indicating a general role in the modulation of cotranscriptional RNA processing events.
Mol Cell 1999 May
PMID:Specific transcriptional pausing activates polyadenylation in a coupled in vitro system. 1036 Jan 75

Phosphorylation of the yeast transcription factor GAL4 at S699 is required for efficient galactose-inducible transcription. We demonstrate that this site is a substrate for the RNA polymerase holoenzyme-associated CDK SRB10. S699 phosphorylation requires SRB10 in vivo, and this site is phosphorylated by purified SRB10/ SRB11 CDK/cyclin in vitro. RNA Pol II holoenzymes purified from WT yeast phosphorylate GAL4 at sites observed in vivo whereas holoenzymes from srb10 yeast are incapable of phosphorylating GAL4 at S699. Mutations at GAL4 S699 and srb10 are epistatic for GAL induction, demonstrating that SRB10 regulates GAL4 activity through this phosphorylation in vivo. These results demonstrate a function for the SRB10/ CDK8 holoenzyme-associated CDK that involves regulation of transactivators by phosphorylation during transcriptional activation.
Mol Cell 1999 May
PMID:GAL4 is regulated by the RNA polymerase II holoenzyme-associated cyclin-dependent protein kinase SRB10/CDK8. 1036 Jan 83

DNA polymerase epsilon (Pol epsilon) is believed to play an essential catalytic role during eukaryotic DNA replication and is thought to participate in recombination and DNA repair. That Pol epsilon is essential for progression through S phase and for viability in budding and fission yeasts is a central element of support for that view. We show that the amino-terminal portion of budding yeast Pol epsilon (Pol2) containing all known DNA polymerase and exonuclease motifs is dispensable for DNA replication, DNA repair, and viability. However, the carboxy-terminal portion of Pol2 is both necessary and sufficient for viability. Finally, the viability of cells lacking Pol2 catalytic function does not require intact DNA replication or damage checkpoints.
Mol Cell 1999 May
PMID:DNA polymerase epsilon catalytic domains are dispensable for DNA replication, DNA repair, and cell viability. 1036 Jan 84

The Rad25 protein in yeast is a DNA helicase and a subunit of the general transcription factor TFIIH. While in vitro studies have led to the hypothesis that TFIIH helicase activity plays a role in promoter melting, in vivo tests are lacking. Using potassium permanganate, which preferentially modifies single-stranded DNA, we show that a temperature-sensitive rad25(ts) mutant severely reduces the normally extensive promoter melting observed in vivo on the highly expressed genes TDH2 and PDC1 and on the induced heat shock gene HSP82. Loss of promoter melting can be observed in as little as 30 s after a shift to the nonpermissive temperature and is accompanied by a dramatic reduction in transcription. These effects on the promoter are specific, since the mutation does not affect TATA box occupancy or, in the case of HSP82, recruitment of TATA-binding protein to the TATA element or that of heat shock factor to heat shock elements. Additionally, using the technique of formaldehyde cross-linking coupled with restriction endonuclease cleavage and ligation-mediated PCR, we were able to map the polymerase density on the promoter of HSP82. This high-resolution mapping allowed us to determine that the polymerase II (Pol II) density on the promoter is also dramatically reduced after inactivation of TFIIH. These data provide strong support for the hypothesis that TFIIH functions with Pol II in the transcriptionally required step of promoter melting and show, surprisingly, that the extent of TFIIH-dependent promoter melting observed in vivo is several times larger than that seen in vitro.
Mol Cell Biol 1999 Aug
PMID:Transcription factor TFIIH is required for promoter melting in vivo. 1040 54

MCMs are a family of proteins related to ATP-dependent helicases that bind to origin recognition complexes and are required for initiation of DNA replication. We report that antibodies against MCM2(BM28) specifically inhibited transcription by RNA polymerase II (Pol II) in microinjected Xenopus oocytes. Consistent with this observation, MCM2 and other MCMs copurified with Pol II and general transcription factors (GTFs) in high-molecular-weight holoenzyme complexes isolated from Xenopus oocytes and HeLa cells. Pol II and GTFs also copurified with MCMs isolated by anti-MCM3 immunoaffinity chromatography. MCMs were specifically displaced from the holoenzyme complex by antibody against the C-terminal domain (CTD) of Pol II. In addition, MCMs bound to a CTD affinity column, suggesting that their association with holoenzyme depends in part on this domain of Pol II. These results suggest a new function for MCM proteins as components of the Pol II transcriptional apparatus.
Mol Cell Biol 1999 Sep
PMID:MCM proteins are associated with RNA polymerase II holoenzyme. 1045 62

This study describes a potential new function of hnRNP U as an RNA polymerase (Pol II) elongation inhibitor. We demonstrated that a subfraction of human hnRNP U is associated with the Pol II holoenzyme in vivo and as such recruited to the promoter as part of the preinitiation complex. hnRNP U, however, appears to dissociate from the Pol II complex at the early stage of transcription and is therefore absent from the elongating Pol II complex. When tested in the human immunodeficiency virus type 1 transcription system, hnRNP U inhibits elongation rather than initiation of transcription by Pol II. This inhibition requires the carboxy-terminal domain (CTD) of Pol II. We showed that hnRNP U can bind TFIIH in vivo under certain conditions and inhibit TFIIH-mediated CTD phosphorylation in vitro. We find that the middle domain of hnRNP U is sufficient to mediate its Pol II association and its inhibition of TFIIH-mediated phosphorylation and Pol II elongation. The abilities of hnRNP U to inhibit TFIIH-mediated CTD phosphorylation and its Pol II association are necessary for hnRNP U to mediate the repression of Pol II elongation. Based on these observations, we suggest that a subfraction of hnRNP U, as a component of the Pol II holoenzyme, may downregulate TFIIH-mediated CTD phosphorylation in the basal transcription machinery and repress Pol II elongation. With such functions, hnRNP U might provide one of the mechanisms by which the CTD is maintained in an unphosphorylated state in the Pol II holoenzyme.
Mol Cell Biol 1999 Oct
PMID:hnRNP U inhibits carboxy-terminal domain phosphorylation by TFIIH and represses RNA polymerase II elongation. 1049 Jun 22

Translesion synthesis (TLS) in Saccharomyces cerevisiae requires at least Rev1p and polymerase zeta (Pol zeta), a complex of the Rev3 polymerase and its accessory factor Rev7p. Although their precise role(s) are poorly characterized, in vitro studies suggest that each protein contributes to TLS in a manner dependent on the particular lesion and surrounding DNA sequence. In the present study, strand segregation analysis is used to attempt to identify the role(s) of the Rev1 and Rev7 proteins during TLS. This assay uses double-stranded plasmids containing a genetic marker opposite to a replication blocking lesion (N-2-acetylaminofluorene; AAF) to measure TLS quantitatively and qualitatively in vivo. The AAF adduct is localized within a repetitive sequence in a manner that allows the formation of misaligned primer-template replication intermediates. Elongation from a misaligned intermediate fixes a frameshift mutation (slipped TLS), while extension of the correctly aligned lesion terminus yields error-free (non-slipped) TLS. The results indicate that there is a strong requirement for Rev7p during Pol zeta-mediated TLS measured in vivo. Furthermore, Rev1p is needed only for non-slipped TLS; slipped TLS remains efficient in its absence, revealing a previously uncharacterized Rev1p activity similar to Escherichia coli UmuDC function. Specifically, this activity is required for elongation from a correctly aligned lesion terminus.
Mol Microbiol 1999 Oct
PMID:Distinct roles for Rev1p and Rev7p during translesion synthesis in Saccharomyces cerevisiae. 1054 Feb 91

Strains of the yeast Saccharomyces cerevisiae defective in transcription factor UAF give rise to variants able to grow by transcribing endogenous ribosomal DNA (rDNA) by RNA polymerase II (Pol II). We have demonstrated that the switch to growth using the Pol II system consists of two steps: a mutational alteration in UAF and an expansion of chromosomal rDNA repeats. The first step, a single mutation in UAF, is sufficient to allow Pol II transcription of rDNA. In contrast to UAF mutations, mutations in Pol I or other Pol I transcription factors can not independently lead to Pol II transcription of rDNA, suggesting a specific role of UAF in preventing polymerase switch. The second step, expansion of chromosomal rDNA repeats to levels severalfold higher than the wild type, is required for efficient cell growth. Mutations in genes that affect recombination within the rDNA repeats, fob1 and sir2, decrease and increase, respectively, the frequency of switching to growth using Pol II, indicating that increased rDNA copy number is a cause rather than a consequence of the switch. Finally, we show that the switch to the Pol II system is accompanied by a striking alteration in the localization and morphology of the nucleolus. The altered state that uses Pol II for rDNA transcription is semistable and heritable through mitosis and meiosis. We discuss the significance of these observations in relation to the plasticity of rDNA tandem repeats and nucleolar structures as well as evolution of the Pol I machinery.
Mol Cell Biol 1999 Dec
PMID:Transcription factor UAF, expansion and contraction of ribosomal DNA (rDNA) repeats, and RNA polymerase switch in transcription of yeast rDNA. 1056 80


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