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)

The beta and beta' subunits of RNA polymerase are thought to be controlled by a translational feedback mechanism regulated by the concentration of RNA polymerase holoenzyme. To study this regulation in vivo, an inducible RNA polymerase overproduction system was developed. This system utilizes plasmids from two incompatibility groups that carry RNA polymerase subunit genes under lac promoter/operator control. When the structural genes encoding the components of core RNA polymerase (alpha, beta and beta') or holoenzyme (alpha, beta, beta' and sigma 70) are present on the plasmids, induction of the lac promoter results in a two fold increase in the concentration of functional RNA polymerase. The induction of RNA polymerase overproduction is characterized by an initial large burst of beta beta' synthesis followed by a gradual decrease as the concentration of RNA polymerase increases. Overproduction of RNA polymerase in a strain carrying an electrophoretic mobility mutation in the rpoB gene results in the specific repression of beta beta' synthesis off the chromosome. These results indicate that RNA polymerase feedback regulation controls beta beta' synthesis in vivo.
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PMID:Feedback regulation of RNA polymerase subunit synthesis after the conditional overproduction of RNA polymerase in Escherichia coli. 301 42

Antiserum to a multisubunit DNA-dependent RNA polymerase from vaccinia virions was prepared to carry out genetic studies. This antiserum selectively inhibited the activity of the viral polymerase but had no effect on calf thymus RNA polymerase II. The specificity of the antiserum was further demonstrated by immunoprecipitation of RNA polymerase subunits from dissociated virus particles. The presence in vaccinia virus-infected cells of mRNA that encodes the polymerase subunits was determined by in vitro translation. Immunoprecipitable polypeptides with Mrs of about 135,000, 128,000, 36,000, 34,000, 31,000, 23,000, 21,000, 20,000, and 17,000 were made when early mRNA was added to reticulocyte extracts. The subunits were encoded within the vaccinia virus genome, as demonstrated by translation of early mRNA that hybridized to vaccinia virus DNA. The locations of the subunit genes were determined initially by hybridization of RNA to a series of overlapping 40-kilobase-pair DNA fragments that were cloned in a cosmid vector. Further mapping was achieved with cloned HindIII restriction fragments. Results of these studies indicated that RNA polymerase subunit genes are transcribed early in infection and are distributed within the highly conserved central portion of the poxvirus genome in HindIII fragments E, J, H, D, and A.
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PMID:DNA-dependent RNA polymerase subunits encoded within the vaccinia virus genome. 303 8

The purpose of this study was to determine the relationship between putative chloroplast RNA polymerase subunit genes and known chloroplast transcriptional activities. We have prepared fusion polypeptide genes from fragments of chloroplast DNA homologous to bacterial RNA polymerase subunit genes and expression vectors carrying portions of the anthranilate synthetase gene (trpE). Fusion proteins for chloroplast homologs of the RNA polymerase alpha (rpoA), beta (rpoB), and beta' (rpoC) subunits were obtained from these genes. The fusion polypeptides synthesized by Escherichia coli in vivo were purified and used as antigens for production of rabbit polyclonal anti-RNA polymerase subunit-specific antibodies. The purified antibodies were able to immobilize chloroplast DNA-dependent RNA polymerases from spinach, pea, and Euglena gracilis. In addition, the soluble chloroplast RNA polymerase activity in tRNA and mRNA synthesis was strongly inhibited by these antibodies under conditions which had little effect on transcription by the chloroplast transcriptionally active chromosome that preferentially transcribed rRNA genes (Greenberg, B. M., Narita, J. O., DeLuca-Flaherty, C., Gruissem, W., Rushlow, K. A., and Hallick, R. B. (1984) J. Biol. Chem. 259: 14880-14887). From these data we conclude that the chloroplast genes homologous to bacterial RNA polymerase subunit genes are expressed in vivo and that the protein products specify at least three of the components of the chloroplast RNA polymerase(s) involved in tRNA and mRNA transcription.
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PMID:Chloroplast rpoA, rpoB, and rpoC genes specify at least three components of a chloroplast DNA-dependent RNA polymerase active in tRNA and mRNA transcription. 304 74

Using DNA encoding the largest subunit of Drosophila melanogaster RNA polymerase II, we isolated the homologous hamster RPO21 gene. Nucleotide sequencing of both the hamster and D. melanogaster RPO21 DNAs confirmed that the RPO21 polypeptides of these two species, like the Saccharomyces cerevisiae RPO21 polypeptide, contain both an N-terminal region homologous to the Escherichia coli RNA polymerase subunit beta' and a unique polymerase II-specific C-terminal domain. This C-terminal domain, encoded by separate exons in the D. melanogaster and hamster genes, consists of a tandemly repeated heptapeptide sequence. By constructing a series of deletions in DNA encoding the 26 heptapeptide repeats normally present in the S. cerevisiae RPO21 polypeptide, we have established that a minimum of between 9 and 11 repeats is necessary for RPO21 function in yeast cells. Replacement of the yeast RPO21 heptapeptide repeats by the longer hamster repetitive domain resulted in viable yeast cells with no detectable mutant phenotype, while a similar replacement of the yeast repeats by the more divergent D. melanogaster repeats was a recessive lethal mutation. We suggest that this novel repetitive domain is essential for proper initiation of transcription by RNA polymerase II and that it may mediate the functions of TATA boxes, upstream activating sequences, and enhancers.
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PMID:The C-terminal domain of the largest subunit of RNA polymerase II of Saccharomyces cerevisiae, Drosophila melanogaster, and mammals: a conserved structure with an essential function. 312 24

The sigma-factor composition of Bacillus subtilis RNA polymerase alters during endospore formation. The best-documented change is the appearance of a major sporulation-specific sigma factor (sigma epsilon), which is an RNA polymerase subunit readily detected at 2 to 4 h into the 8-h sporulation process. To determine the nature of the RNA polymerase in differentiating cells after the period of sigma epsilon abundance, we isolated RNA polymerase from cells that were harvested at 6 h after the onset of sporulation. Highly purified fractions of RNA polymerase from these cells contained at least six proteins which cosedimented with core RNA polymerase (beta beta' alpha 2) during glycerol gradient centrifugation. Most of these proteins were in the size range of 20,000 to 29,000 daltons, although one 90,000-dalton protein was also evident. None of the putative RNA polymerase subunits were present in quantities similar to that observed for sigma epsilon during its period of prominence in the cell but instead resembled the minor vegetative-cell sigma factors in abundance. In vitro transcriptions using cloned B. subtilis DNAs as templates revealed at least two novel transcriptional activities in the enzyme that was isolated from cells at 6 h after the onset of sporulation but absent in an RNA polymerase preparation extracted from cells at 4 h after the onset of sporulation. One of these activities was reconstituted by the addition of a 25,000 to 27,000-dalton protein fraction to core RNA polymerase.
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PMID:Characteristics of an RNA polymerase population isolated from Bacillus subtilis late in sporulation. 314 58

Three Caulobacter crescentus heat-shock proteins were shown to be immunologically related to the Escherichia coli heat-shock proteins GroEL, Lon and DnaK. A fourth heat-shock protein was detected with antibody to the C. crescentus RNA polymerase. This 37,000 Mr heat-shock protein might be related to the E. coli 32,000 Mr heat-shock sigma subunit. The synthesis of the major C. crescentus RNA polymerase sigma factor was not induced by heat shock. The E. coli GroEL protein and the related protein from C. crescentus were also induced by treatment with hydrogen peroxide. Like some of the proteins in the heat-shock protein families of Drosophila and yeast, the four heat-shock proteins in C. crescentus were found to be regulated developmentally under normal conditions. All four proteins were synthesized in the predivisional cell, but the progeny showed cell type-specific bias in the level of enhanced synthesis after heat shock. The 92,000 Mr Lon homolog and the 37,000 Mr RNA polymerase subunit were preferentially synthesized in the stalked cell, whereas the synthesis of the 62,000 Mr GroEL homolog was enhanced in the progeny swarmer cell. Furthermore, the four heat-shock proteins synthesized in the predivisional cell were partitioned in a specific manner upon cell division. The stalked cell, which initiates chromosome replication immediately upon division, received the Lon homolog, the DnaK homolog and the 37,000 Mr RNA polymerase subunit. The GroEL homolog, however, was distributed equally to both the stalked cell and the swarmer cell. These results provide access to the functions of C. crescentus heat-shock proteins under both normal and stress conditions. They also allow an investigation of the regulatory signals that modulate the asymmetric distribution of proteins and their subsequent cell type-specific expression in the initial stages of a developmental program.
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PMID:Asymmetric segregation of heat-shock proteins upon cell division in Caulobacter crescentus. 330 28

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

An isogenic pair of relA+ and relA strains of Escherichia coli B/r with a mutation in the RNA polymerase subunit gene rpoB (Rifr) was isolated in which the relationship between guanosine tetraphosphate (ppGpp) concentration and stable RNA (rRNA, tRNA) gene activity was altered. The RNA polymerase in the rpoB strains was found to be about 20-fold more sensitive to ppGpp with respect to its stable RNA promoter activity than was the wild-type enzyme. The existence of such mutants is consistent with the idea that ppGpp interacts with the RNA polymerase enzyme and thereby alters its promoter selectivity, i.e., reduces its affinity for the stable RNA promoters. Under most conditions, the rpoB mutants had a reduced rate of growth and about a 10-fold-reduced intracellular concentration of ppGpp compared with the rpoB wild-type strains. The reduction of the level of ppGpp in the rpoB mutants during exponential growth was presumably a reflection of an indirect effect of the rpoB mutation on the control of relA-independent ppGpp metabolism.
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PMID:rpoB mutation in Escherichia coli alters control of ribosome synthesis by guanosine tetraphosphate. 618 47

Using the in vitro mixed transcription system (Kajitani and Ishihama (1983a, 1983b), we examined selective transcription of truncated DNA templates carrying lac(UV5), rrnE or rpsA promoters by RNA polymerase holoenzymes from pairs of wild-type parents and mutants with a mutation in one or more RNA polymerase subunit genes. The promoter selectivity of RNA polymerases from two sigma-subunit mutants carrying either rpoD2 or rpoD285 differed markedly from that of the respective wild-type enzymes. Both the parental RNA polymerases, however, exhibited abnormal promoter selectivity compared with holoenzymes from various wild-type E. coli strains. On the other hand, all the RNA polymerases from rpoB and/or rpoC mutants and the respective wild-type parents were similar, if not identical, in promoter selection at low temperature. At high temperature, however, RNA polymerases from mutants carrying rpoB2B7 and rpoC4, affecting the beta and beta' subunits, respectively, showed decreased transcription from the high-affinity slow-transcribable promoter rrnEp2 whereas the rpoC92 and rpoB906 X rpoC907 mutant enzymes both lost transcription activity from the strong promoter lacP(UV5). Taking all these observations together we conclude that not only the sigma subunit but also the beta and beta' subunits are involved in the recognition of promoters.
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PMID:Promoter selectivity of Escherichia coli RNA polymerase. II: Altered promoter selection by mutant holoenzymes. 636

Amber mutations in the rpoB gene specifying the beta subunit of RNA polymerase coupled with conditional amber suppressors were used to restrict the synthesis of core RNA polymerase in strains of Escherichia coli. Such a restriction stimulated transcription of genetic units containing RNA polymerase subunit genes. Within the L10 transcription unit (genetic structure: promotor (PL10), rplJ (L10), rplL (L7/L12), attenuator, rpoB (beta), rpoC (beta'), terminator), the initiation of transcription at the promotor was enhanced and termination at the transcription attenuator was relaxed. Transcription of the genetic unit containing the rpoA gene (alpha) was also enhanced. In the strain containing a non-polar amber mutation, the synthesis rate of the beta' subunit protein during the restriction correlated with the level of transcription of the beta and beta' genes. In contrast, synthesis of L7/L12 ribosomal protein remained essentially unaltered in spite of the elevated levels of L10-L7/L12 mRNA.
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PMID:Regulation of RNA polymerase synthesis. Conditional lethal amber mutations in the beta subunit gene. 698 28


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