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)

A Polymyxin B-sensitive mutant of Salmonella typhimurium (Pox-1) channels all infecting wild-type P22 toward lysogenization. The efficiency of this channeling is sufficiently high that P22c+ (wild type) cannot form plaques on Pox-1; phage mutants defective in repressor synthesis (P22c1, c2, c3) or refractory toward repressor (P22vir B) can form plaques. The lytic growth of all phages which have a functional c1 gene is retarded in Pox-1; this retardation is seen even in phages which cannot make repressor. We present experiments which are consistent with the explanation that the retardation is an exaggeration of a normal regulatory event. In a wild-type host, P22 genes c1 and c3 products, host RNA polymerase, and other host factors (?) interact at a promotor site (c27) IN THE PHAGE DNA. This interaction promotes repressor synthesis and represses transcription of lytic genes. In the mutant Pox-1, a host product involved in viral DNA synthesis and transcription is altered. The altered host product results in stronger retardation of lytic gene transcription. The importance of this interaction in the decision between lysis and lysogeny is discussed. The mutant Pox-1 alters the expression or activity of another phage gene. Gene c3 product is absolutely required for lysogenization in this host, although it is not so required in wild-type S. typhimurium.
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PMID:Host influence on the activity of genes c1 and c3 in regulating the decision between lysis and lysogency in bacteriophage P22. 17 49

A rifampin-resistant mutant of Salmonella typhimurium carries an altered RNA polymerase. Wild-type (c+) phage P22 displays clear plaques and a reduced lysogenization frequency on this mutant host. The cly mutants of P22 were isolated on the basis of their ability to lysogenize such mutant hosts. Two classes of regulatory events, both of which are dependent on P22 gene c1 activity, are necessary for the establishment of lysogeny in P22. The positive events culminate in repressor synthesis; the negative events cause a retardation in phage DNA synthesis. Neither the positive nor the negative events are observed in P22c+ infections of the mutant host. Both effects are found in P22cly infections of the mutant host. Observable results of both the negative and the positive events are exaggerated in P22cly infections of wild-type hosts as compared to P22c+ infections. The cly mutation apparently increases the positive and negative regulatory events so that they are detectable in the mutant host and exaggerated in wild-type hosts. Possible mechanisms that result in the high frequency of lysogenization that characterizes the cly mutation and the nature of the cly mutation are discussed.
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PMID:Regulation of Bacteriophage P22 DNA synthesis and repressor levels in P22cly infections. 32 6

The product of phage P22 gene c1 has two functions: (1) it promotes synthesis of repressor and (2) during the first minutes of infection it retards expression of some lytic genes. We call the second, negative function "c1 retardation". We investigated c1 retardation in a mutant host of Salmonella typhimurium that is resistant to rifampicin and carries an altered RNA polymerase. No c1 retardation of DNA synthesis was detectable in this host after infection with wild-type phages. This elimination of the normally detectable c1 function leads to the conclusion that the mutant RNA polymerase interferes with the expression of c1 gene activity. Wild-type genes form clear plaques on the mutant host. Mutants of P22 called cly were isolated by others. These mutants form turbid plaques on the altered RNA polymerase host. Infections with P22 cly in the mutant host resulted in detectable c1 retardation. The cly mutation therefore restores c1 activity in a host which wild-type c1 is not expressed. Two spontaneous mutants were isolated from the mutant host. These two strains allowed partial expression of c1 retardation, although they remained rifampicin resistant. We interpret our data to indicate that expression of the normal functions of the gene c1 product requires an interaction of that product with the host RNA polymerase.
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PMID:Effect of mutant host RNA polymerase on the bifunctional activities of P22 gene c1. 32 18

We cloned, expressed, and purified the positive regulatory protein C1 of the temperate phage P22 of Salmonella typhimurium. The purified protein was characterized as to its amino acid composition, protein sequence, molecular weight, and antigenicity. P22 C1 was shown to be a tetrameric protein composed of four identical subunits with M(r) = 10,000. Moreover, we identified and characterized two P22 C1-dependent phage promoters, P(RE) and Pa23, whose function was completely dependent on C1 both in vitro and in vivo. These two promoters share a common TTGCN6TTGC/T motif in their -35 regions, the same motif recognized by the analogous phage lambda transcription activator protein cII. P22 C1 protein bound selectively to this region and centered on the TTGC repeat motif. Binding and transcription experiments demonstrated that the two promoters respond coordinately to C1 activation. Last, in contrast to lambda cII, the C1 protein exhibited little cooperativity with Escherichia coli RNA polymerase for DNA binding, but because of its stronger inherent binding ability, achieved an overall promoter affinity similar to that observed for cII at its cognate promoter signals.
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PMID:Characterization of the transcription activator protein C1 of bacteriophage P22. 138 14

Expression of the rpoBC genes encoding the beta and beta' RNA polymerase subunits of Escherichia coli is autogenously regulated. Although previous studies have demonstrated a post-transcriptional feedback mechanism, complex transcriptional controls of rpoBC expression may also contribute. We show that an attenuator (rpoBa) separating the ribosomal protein (rpl) genes from the rpoBC genes in the rplKAJLrpoBC gene cluster is modulated in its efficiency in response to changes in the frequency of transcription initiated by promoters located upstream. A series of rplJLrpoBalacZ transcriptional fusions was constructed on lambda vectors in which transcription into the rpoBa attenuator was varied by using a variety of promoters with different strengths. beta-galactosidase assays performed on monolysogens of the recombinant phage show that with transcription increasing over a 40-fold range, readthrough of rpoBa decreases from 61% to 19%. In contrast, two other well-characterized terminators show nearly constant efficiencies over a similar range of transcription frequencies. Using a set of phage P22 ant promoter variants with single-nucleotide changes in the promoter consensus sequences also demonstrates that the modulation of rpoBa function appears to be unrelated to the phenomenon of 'factor-independent antitermination' reported by others. The implications for autogenous control of RNA polymerase synthesis are discussed.
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PMID:Transcription frequency modulates the efficiency of an attenuator preceding the rpoBC RNA polymerase genes of Escherichia coli: possible autogenous control. 140 90

A G----T mutation at the start-point of transcription of the phage P22 sar promoter (sar + 1T) causes a novel defect in promoter clearance by Escherichia coli RNA polymerase (RNAP) in vitro. Under standard transcription conditions, in the presence of high concentrations of all four NTPs, the predominant products from this promoter are poly(U) chains of varying length. Because the mutation creates a run of four T: A base-pairs from - 1 to +3 (TGTT----TTTT), we propose that synthesis of poly(U) is pseudo-templated by the A4 stretch on the template strand. G----A and G----C mutations at position +1 do not cause pseudo-templated transcription. Several molecules of poly(U) are produced and released per sar+1T promoter-polymerase complex without dissociation of RNAP from the template DNA. The exponential relationship between yield and size of individual poly(U) species indicates that there is a constant probability that another U residue will be added to the nascent chain. Presumably, pseudo-templated transcription occurs by a slippage (stuttering) mechanism like that proposed to explain certain kinds of RNA editing in eukaryotic viral mRNAs.
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PMID:Pseudo-templated transcription by Escherichia coli RNA polymerase at a mutant promoter. 170 Nov 52

A sequence of 163 amino acids was derived from the nucleotide sequence of a DNA fragment bearing the colitis phage lytic enzyme gene. The molecular weight, basicity and the sequence of the three N-terminal amino acids agreed with those of the phage lytic enzyme. The amino acids at the N-terminal of the colitis phage enzyme are homologous with those of T4, P22 and phi 29 phage lysozymes, to the extent of 18-34%. The transcription initiation site was mapped at 166 nucleotides upstream to the translation initiation codon, ATG. The Shine-Dalgarno sequence, the Pribnow box and the RNA polymerase recognition site were at 5.10 and 35 nucleotdies respectively, upstream to the transcription initiation site. The transcription termination signal, (the inverted repeat) and the termination site (the oligo TS) were at 7 and 28 nucleotides respectively, downstream to the translation termination site, TAA.
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PMID:Structure of colitis phage lytic enzyme gene. 208 Sep 17

Ordered development of lambdoid phages relies on systems of transcription termination and antitermination. The phage-encoded N early regulatory proteins, acting with the Nus proteins of Escherichia coli, modify RNA polymerase to a form that overrides many transcription termination signals. These modifications require cis-acting sites, nut, located downstream of the early phage promoters. The nut sites in phages lambda, 21, and P22, which share similarities but are not identical, contain two signals, boxA and boxB. We demonstrate that although a consensus sequence for the boxA signal (boxAcon), 5'CGCTCTTTA, is found only in P22, changes to consensus in the nutR sites of lambda and 21 create more effective antitermination signals than the wild-type signals. An in vivo competition assay demonstrates that a lambda nut region with boxAcon outcompetes nut regions with wild-type, as well as other variations of the boxA sequence, for the host NusB protein. This suggests that boxA influences NusB activity in N-mediated antitermination. Successful competition by boxAcon requires transcription of the nut site as well as N activation. Nucleotide replacement further demonstrates that bases at both ends of boxA are important for antitermination.
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PMID:Transcription-dependent competition for a host factor: the function and optimal sequence of the phage lambda boxA transcription antitermination signal. 214 36

Two-dimensional crystals of yeast RNA polymerase A (I) were obtained by interaction with positively charged lipid layers. The analysis of single molecular images of lipid-bound RNA polymerases showed that the enzyme was preferentially oriented by the lipid phase, which probably facilitated crystallization. Electron micrographs of the crystals revealed a rectangular unit cell 25.8 nm by 45.6 nm in size containing four RNA polymerase dimers related by P22(1)2(1) symmetry. The projection map showed, at about 2.5 nm resolution, two different views of the enzyme characterized by two bent arms, which appeared to cross at one end. These arms are likely to contain the A190 and A135 subunits and delimit a 3 to 4 nm wide groove. Additional structural features were observed and compared to the Escherichia coli enzyme.
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PMID:Structural study of the yeast RNA polymerase A. Electron microscopy of lipid-bound molecules and two-dimensional crystals. 225 34

We have dissected the protein and nucleic acid determinants that direct a group of transcriptional antiterminators to their specific target operons. These antiterminators, the N gene products of phages lambda, 21, and P22, function solely with their respective recognition sites, nut, to modify RNA polymerase to a termination-resistant form. We demonstrate that a unique hairpin sequence within each nut site, called boxB, confers genome specificity by interacting with a small amino-terminal domain of the cognate N protein. This interaction is dependent upon an arginine-rich subdomain, which is conserved not only among the N proteins but also in many RNA binding proteins from ribosomes and RNA virus capsids. Notably, this motif constitutes an essential domain of the HIV protein Tat whose function as a trans-activator requires a specific hairpin sequence.
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PMID:Sequence-specific recognition of RNA hairpins by bacteriophage antiterminators requires a conserved arginine-rich motif. 247 56


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