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)

While preferential repair of the transcribed strands within active genes has been demonstrated in organisms as diverse as humans and Escherichia coli, it has not previously been shown to occur in chromosomal genes in the yeast Saccharomyces cerevisiae. We found that repair of cyclobutane pyrimidine dimers in the transcribed strand of the expressed RPB2 gene in the chromosome of a repair-proficient strain is much more rapid than that in the nontranscribed strand. Furthermore, a copy of the RPB2 gene borne on a centromeric ARS1 plasmid showed the same strand bias in repair. To investigate the relation of this strand bias to transcription, we studied repair in a yeast strain with the temperature-sensitive mutation, rpb1-1, in the largest subunit of RNA polymerase II. When exponentially growing rpb1-1 cells are shifted to the nonpermissive temperature, they rapidly cease mRNA synthesis. At the permissive temperature, both rpb1-1 and the wild-type, parental cells exhibited rapid, proficient repair in the transcribed strand of chromosomal and plasmid-borne copies of the RPB2 gene. At the nonpermissive temperature, the rate of repair in the transcribed strand in rpb1-1 cells was reduced to that in the nontranscribed strand. These findings establish the dependence of strand bias in repair on transcription by RNA polymerase II in the chromosomes and in plasmids, and they validate the use of plasmids for analysis of the relation of repair to transcription in yeast.
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PMID:Preferential repair of cyclobutane pyrimidine dimers in the transcribed strand of a gene in yeast chromosomes and plasmids is dependent on transcription. 143 66

Mutations in the three largest subunits of yeast RNA polymerase II (RPB1, RPB2, and RPB3) were investigated for their effects on RNA polymerase II structure and assembly. Among 23 temperature-sensitive mutations, 6 mutations affected enzyme assembly, as assayed by immunoprecipitation of epitope-tagged subunits. In all six assembly mutants, RNA polymerase II subunits synthesized at the permissive temperature were incorporated into stably assembled, immunoprecipitable enzyme and remained stably associated when cells were shifted to the nonpermissive temperature, whereas subunits synthesized at the nonpermissive temperature were not incorporated into a completely assembled enzyme. The observation that subunit subcomplexes accumulated in assembly-mutant cells at the nonpermissive temperature led us to investigate whether these subcomplexes were assembly intermediates or merely byproducts of mutant enzyme instability. The time course of assembly of RPB1, RPB2, and RPB3 was investigated in wild-type cells and subsequently in mutant cells. Glycerol gradient fractionation of extracts of cells pulse-labeled for various times revealed that a subcomplex of RPB2 and RPB3 appears soon after subunit synthesis and can be chased into fully assembled enzyme. The RPB2-plus-RPB3 subcomplexes accumulated in all RPB1 assembly mutants at the nonpermissive temperature but not in an RPB2 or RPB3 assembly mutant. These data indicate that RPB2 and RPB3 form a complex that subsequently interacts with RPB1 during the assembly of RNA polymerase II.
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PMID:Mutations in the three largest subunits of yeast RNA polymerase II that affect enzyme assembly. 171 23

A sensitive phenotypic assay has been used to identify mutations affecting transcription initiation in the genes encoding the two large subunits of Saccharomyces cerevisiae RNA polymerase II (RPB1 and RPB2). The rpb1 and rpb2 mutations alter the ratio of transcripts initiated at two adjacent start sites of a delta-insertion promoter. Of a large number of rpb1 and rpb2 mutations screened, only a few affect transcription initiation patterns at delta-insertion promoters, and these mutations are in close proximity to each other within both RPB1 and RPB2. The two rpb1 mutations alter amino acid residues within homology block G, a region conserved in the large subunits of all RNA polymerases. The three strong rpb2 mutations alter adjacent amino acids. At a wild-type promoter, the rpb1 mutations affect the accuracy of mRNA start site selection by producing a small but detectable increase in the 5'-end heterogeneity of transcripts. These RNA polymerase II mutations implicate specific portions of the enzyme in aspects of transcription initiation.
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PMID:Mutations in a conserved region of RNA polymerase II influence the accuracy of mRNA start site selection. 192 77

The two large subunits of RNA polymerase II, RPB1 and RPB2, contain regions of extensive homology to the two large subunits of Escherichia coli RNA polymerase. These homologous regions may represent separate protein domains with unique functions. We investigated whether suppressor genetics could provide evidence for interactions between specific segments of RPB1 and RPB2 in Saccharomyces cerevisiae. A plasmid shuffle method was used to screen thoroughly for mutations in RPB2 that suppress a temperature-sensitive mutation, rpb1-1, which is located in region H of RPB1. All six RPB2 mutations that suppress rpb1-1 were clustered in region I of RPB2. The location of these mutations and the observation that they were allele specific for suppression of rpb1-1 suggests an interaction between region H of RPB1 and region I of RPB2. A similar experiment was done to isolate and map mutations in RPB1 that suppress a temperature-sensitive mutation, rpb2-2, which occurs in region I of RPB2. These suppressor mutations were not clustered in a particular region. Thus, fine structure suppressor genetics can provide evidence for interactions between specific segments of two proteins, but the results of this type of analysis can depend on the conditional mutation to be suppressed.
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PMID:Genetic exploration of interactive domains in RNA polymerase II subunits. 218 12

RNA polymerase II subunit composition, stoichiometry, and phosphorylation were investigated in Saccharomyces cerevisiae by attaching an epitope coding sequence to a well-characterized RNA polymerase II subunit gene (RPB3) and by immunoprecipitating the product of this gene with its associated polypeptides. The immunopurified enzyme catalyzed alpha-amanitin-sensitive RNA synthesis in vitro. The 10 polypeptides that immunoprecipitated were identical in size and number to those previously described for RNA polymerase II purified by conventional column chromatography. The relative stoichiometry of the subunits was deduced from knowledge of the sequence of the subunits and from the extent of labeling with [35S]methionine. Immunoprecipitation from 32P-labeled cell extracts revealed that three of the subunits, RPB1, RPB2, and RPB6, are phosphorylated in vivo. Phosphorylated and unphosphorylated forms of RPB1 could be distinguished; approximately half of the RNA polymerase II molecules contained a phosphorylated RPB1 subunit. These results more precisely define the subunit composition and phosphorylation of a eucaryotic RNA polymerase II enzyme.
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PMID:RNA polymerase II subunit composition, stoichiometry, and phosphorylation. 218 13

The Saccharomyces cerevisiae gene encoding the smallest RNA polymerase II subunit, RPB10, was isolated and sequenced. The gene for this subunit is present in single copy and maps to chromosome XV, where two other yeast RNA polymerase II subunits, RPB2 and RPB8, reside. The RPB10 sequence predicts a protein only 46 amino acids in length with a molecular mass of 5400 daltons. Sporulation and tetrad analysis of diploid cells containing one copy of the RPB10 gene and one copy of HIS3 in place of the RPB10 gene revealed that the RPB10 subunit is essential for viability.
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PMID:RNA polymerase II subunit RPB10 is essential for yeast cell viability. 850 44

Saccharomyces cerevisiae RNA polymerase II conditional mutants that selectively disrupt the synthesis of specific mRNAs were isolated. At the permissive temperature, several of the mutants were inositol auxotrophs as a result of inadequate induction of INO1 transcription. The transcriptional defects exhibited by one of these Ino- mutants (rpb2-2) were further investigated. The induction of GAL10 and HIS4 transcription in rpb2-2 strains was similar to that of wild-type strains, in contrast to the lack of induction of INO1 transcription. When shifted to the nonpermissive temperature, cells containing rpb2-2 continued to accumulate some mRNAs but not others. Together, these results indicate that transcription of specific genes can be disrupted by RNA polymerase II mutations. The rpb2-2 allele alters an amino acid residue that occurs in a highly conserved segment of the RPB2 protein and that is shared by homologous subunits in other species.
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PMID:RNA polymerase II mutants defective in transcription of a subset of genes. 240 58

Conditional mutations in the Saccharomyces cerevisiae RNA polymerase II large subunit, RPB1, were obtained by introducing a mutagenized RPB1 plasmid into yeast cells, selecting for loss of the wild-type RPB1 gene, and screening the cells for heat or cold sensitivity. Sequence analysis of 10 conditional RPB1 mutations and 10 conditional RPB2 mutations revealed that the amino acid residues altered by these distinct mutations are nearly always invariant among eucaryotic RPB1 and RPB2 homologs. These results suggest that RNA polymerase mutants might be obtained in other eucaryotic organisms by alteration of these invariant residues.
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PMID:Conditional mutations occur predominantly in highly conserved residues of RNA polymerase II subunits. 240 67

Reversion analysis has identified four suppressor genes that permit transcription of the Saccharomyces cerevisiae HIS4 gene in the absence of GCN4, BAS1, and BAS2, trans-acting proteins normally required for activation of HIS4 transcription. These suppressor genes encode factors that affect the transcription of many diverse genes. Two of these suppressors, SIT1 and SIT2, are encoded by RPB1 and RPB2, the genes for the two largest subunits of RNA polymerase II. All strains containing suppressor mutations in RPB1 and RPB2 have reduced transcription of the INO1 gene and an inositol requirement. Mutations in SIT3 or high copy number SIT3 increase HIS4 transcription in the absence of GCN4, BAS1, and BAS2. This increase in HIS4 transcription by high copy number SIT3 or by sit3 alleles is largely independent of the HIS4 TATA sequence. The SIT4 protein is over 50% identical to the catalytic subunit of bovine type 2A protein phosphatase. sit4 mutations in combination with suppressor mutations in RPB1 or RPB2 (sit1, sit4 or sit2, sit4) are lethal, suggesting an interaction between SIT4 and RNA polymerase II.
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PMID:A suppressor of a HIS4 transcriptional defect encodes a protein with homology to the catalytic subunit of protein phosphatases. 253 49

Eukaryotic RNA polymerases are complex aggregates whose component subunits are functionally ill-defined. The gene that encodes the 140,000-dalton subunit of Saccharomyces cerevisiae RNA polymerase II was isolated and studied in detail to obtain clues to the protein's function. This gene, RPB2, exists in a single copy in the haploid genome. Disruption of the gene is lethal to the yeast cell. RPB2 encodes a protein of 138,750 daltons, which contains sequences implicated in binding purine nucleotides and zinc ions and exhibits striking sequence homology with the beta subunit of Escherichia coli RNA polymerase. These observations suggest that the yeast and the E. coli subunit have similar roles in RNA synthesis, as the beta subunit contains binding sites for nucleotide substrates and a portion of the catalytic site for RNA synthesis. The subunit homologies reported here, and those observed previously with the largest RNA polymerase subunit, indicate that components of the prokaryotic RNA polymerase "core" enzyme have counterparts in eukaryotic RNA polymerases.
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PMID:Prokaryotic and eukaryotic RNA polymerases have homologous core subunits. 354 6


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