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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)

In a rifS/rifR heterodiploid strain of E. coli, a 4 minute pulse of rifampicin can induce a prolonged (greater than 60 min) increase in the rate of synthesis of the RNA polymerase subunits, beta and beta'. The application of a constraint on the fidelity of protein synthesis during, but not after, the rifampicin pulse partially arrests the development of this capacity for subunit synthesis. I discuss the implications of these findings in relation to the control of the BB' operon in E. coli.
Mol Gen Genet 1976 Jul 05
PMID:Rifampicin-induced protein synthesis: A pre-requisite for increased expression of the beta beta' operon in Escherichia coli. 78 12

Bacteria with specific temperature sensitive lethal mutations in the gene for the beta' subunit of RNA polymerase synthesize both the beta and beta' subunits at a several fold higher rate at 42 degrees C than wild-type cells relative to total protein. Synthesis of the alpha and sigma subunits proceeds at essentially the wild-type rates under these conditions. In contrast, a mutant with a temperature sensitive lethal mutation in the beta subunit gene synthesizes beta and beta' at 42 degrees C at slightly lower rates than wild-type, while alpha and sigma synthesis is not significantly altered. In all of the mutants at 42 degrees C, newly synthesized alpha subunits are stable, while the beta, beta' and sigma subunits are rapidly degraded. The apparent uncoupling of betabeta' and alpha subunit synthesis seen in the beta' mutants at 42 degrees C might suggest that the synthesis of these subunits is at least in part controlled by different mechanisms.
Mol Gen Genet 1976 Aug 19
PMID:Altered synthesis and stability of RNA polymerase holoenzyme subunits in mutants of Escherichia coli with mutations in the beta or beta' subunit genes. 78 54

ppGpp alters the initiation specificity of RNA polymerase holoenzyme in vitro in a direction which mimics the stringent response in vivo. The transition temperature for opening rRNA promoters is increased by the nucleotide, that for opening phi80 promoters is unaffected. This implies that RNA polymerase can discriminate between different types of promoter. ppGpp may act by effecting a structural change in the enzyme.
Mol Gen Genet 1976 Aug 19
PMID:Modulation of RNA polymerase specificity by ppGpp. 78 60

RNA polymerase from T4 infected cells supplemented with E. coli sigma polypeptide has a lower affinity for rRNA promoters than RNA polymerase from uninfected cells. The pattern of transcription by the phage modified polymerase is qualitatively similar to that of the vegetative polymerase in the presence of ppGpp. We suggest that E. coli polymerase holoenzyme normally exists in at least two conformational states, one with a high affinity for rRNA promoters and another with a low affinity, and that T4 infection stabilises the low affinity form.
Mol Gen Genet 1976 Sep 23
PMID:Phage T4 infection restricts rRNA synthesis by E. coli RNA polymerase. 78 64

RNA polymerase isolated from ts XH56, a conditional lethal mutant unable to grow and synthesize RNA at 42 degrees, was found to be temperature sensitive in vitro. The mutation affects the beta' subunit as determined by mixed reconstitution of isolated subunits from wild-type and mutant enzyme. The mutant RNA polymerase is unstable; addition of glycerol stabilizes the enzyme and increases its activity on native DNA. In addition, the mutant enzymes is sensitive to high ionic strength. Both high temperature and high ionic strength do not affect chain elongation; thus, the mutation renders the enzyme unable either to bind to or melt out promotor sites. From these data we conclude that the beta' subunit plays an important role in promotor selection.
Mol Gen Genet 1976 Sep 23
PMID:Characterization of a ts beta' mutant RNA polymerase of Escherichia coli. 78 68

A specialized transducing bacteriophage lambdadpolCdap D-9 has been isolated that carries the structural gene for EF-Ts1 (tsf). The presence of EF-Ts among the proteins synthesized under the direction of this phage in UVL-inactivated cells has been detected by two-dimensional gel electrophoresis and has been verified by antibody precipitation. In an induced lysogen of this phage the relative rate of synthesis of EF-Ts is increased 4-fold. Evidence is presented which suggest that the structural genes for ribosomal protein S2 (rpsB) and RNA polymerase sigma factor (sit) also lies on lambdadpolCdap D-9.
Mol Gen Genet 1976 Oct 18
PMID:A transducing bacteriophage lambda carrying the structural gene for elongation factor Ts. 79 84

In vitro transcription of the trp operon in isolated nucleoids from Escherichia coli was studied. RNA synthesis in this system occurred primarily as a continuation of transcription which had been initiated in vivo; little or no initiation of new RNA chains was observed. Transcription of the trp operon in nucleoids by endogenous RNA polymerase procedded efficiently and ceases sequentially in the order of the gene sequence within the operon. Under these conditions, no appreciable exonuccleolytic digestion of nascent 3H-RNA was found, though some endonucleolytic cleavage was generally seen. Little or no incorporation of 14C-leucine into polypeptides was observed, inspite of tha fact that considerable number of ribosomes and nascent RNA chains were found attached to the isolated nucleoids. The synthesis of trp mRNA continued in the presence of chloramphenicol or fusidic acid, or under conditions where the rebosomal translocation factor G was inactivated. From these and other kinetic studies of trp mRNA synthesis in nucleoids obtained from nonsense strong polar mutants of the trp operon, it was shown that transcription in nucleoids was not connected functionally with transloational processes and thus unable to exhibit polarity effected by a nonsense mutation or by general translational blockage. In studies employing nucleoids from nonsense strong polar mutants of the trp operon, it was demonstrated that RNA polymerase are scantily distributed over the region downstream from the nonsense mutation site of the operon, thereby supporting a notion that in vivo transcription is eventually terminated near the nonsense mutation.
Mol Gen Genet 1976 Nov 17
PMID:In vitro transcription of the tryptophan operon in isolated bacterial nucleoids. 79 65

The 1400 base pair repeat produced by digestion of calf satellite I DNA (phi = 1.714 g/cm3) with EcoRI, was cloned in E. coli. The hybrid plasmid (pGM 214) which contains the ColE1-Ap vector (pSF 2124) and the 1400 base pair fragment replicates stably in E. coli and can be amplified by chloramphenicol treatment. No clone was found in which more than one "repeat unit" of the satellite I DNA was present in the chimaera plasmid. Digestion of the original satellite I and the plasmid pGM 214 with R-SmaI shows that the satellite DNA replicated in E. coli is cleaved by the restriction endonuclease SmaI whereas the original satellite I DNA from calf thymus is not, suggesting that the satellite I contains a large amount of modified cytosine or guanosine, probably 5-methyl-cytosine. R-EcoRI* produces a number of fragments with the satellite I in the range of 300 base pairs to 1400 base pairs. A physical map of pGM 214 (and pSF 2124) with R-EcoRI, R-HincII, R-HindIII, R-SmaI, R-BamI and R-EclI was constructed. The 1400 base pair "repeat unit" in the pGM 214 is efficiently transcribed in vitro by purified RNA polymerase, starting from a pSF 2124 promoter. The restriction enzyme EclI produces a 350 base pair repeat with calf satellite II (phi = 1,722 g/cm3), whereas the satellite I is not cut by this enzyme.
Mol Gen Genet 1976 Nov 24
PMID:Cloning of calf thymus satellite I DNA in Escherichia coli. 79 69

A speculative model based on published sequences to explain the specific binding of RNA polymerase of E. coli to promoters is suggested: (see article). A fragment 24 base pairs long to the left of the initiation site must not contain the G's in the positions indicated by the circles and must contain T's (or G's) in the positions marked by the squares. In most known cases mutual disposition of the circle and square patterns is as shown above. In one case (the fd G3 promoter) the pattern of squares is shifted by 4 base pairs to the right relative to the pattern of universal non-G's (circles).
Mol Biol Rep 1976 Nov
PMID:A model of promoter recognition along the two helical grooves of DNA. 79 87

The effects of a partial restriction of valyl-tRNA aminoacylation on the synthesis of aminoacyl-tRNA synthetases, ribosomal proteins, and other translation and transcription proteins were examined in otherwise isogenic stringent (relA+) and relaxed (relA1) derivatives of E. coli B. The synthesis of individual ribosomal proteins, elongation factor G, and to a lesser extent elongation factors Tu and Ts, and the valyl- and arginyl-tRNA synthetases was found to be subject to the influence of the stringent control system. The synthesis of the alpha and beta subunits of RNA polymerase and several of the aminoacyl-tRNA synthetases, in contrast, is either not subject to the influence of the stringent control system, or is subject to additional regulatory constraints.
Mol Gen Genet 1976 Dec 22
PMID:The effects of the relA gene on the synthesis of aminoacyl-tRNA synthetases and other transcription and translation proteins in Escherichia coli A. 79 47


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