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 synthetic gene of yeast aspartic acid tRNA with a promoter for phage T7 RNA polymerase was cloned in Escherichia coli. The in vitro transcribed tRNA(Asp) molecules are deprived of modified nucleotides and retain their aspartylation capacity. The solution conformation of these molecules was mapped with chemical structural probes and compared to that of fully modified molecules. Significant differences in reactivities were observed in Pb2+ cleavage of the RNAs and in modification of the bases with dimethyl sulphate. The most striking result concerns C56, which becomes reactive in unmodified tRNA(Asp), indicating the disruption of the C56-G19 base pair involved in the D- and T-loop interaction. The chemical data indicate that unmodified tRNA(Asp) transcripts possess a relaxed conformation compared to that of the native tRNA. This conclusion is confirmed by thermal melting experiments. Thus it can be proposed that post-transcriptional modifications of nucleotides in tRNA stabilize the biologically active conformations in these molecules.
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PMID:Conformation in solution of yeast tRNA(Asp) transcripts deprived of modified nucleotides. 207 90

The effects of 14 metal ions (chlorides) on the transcription of calf thymus DNA and phage T4 DNA with Escherichia coli RNA polymerase were tested. These assays were conducted under improved conditions of lower pH and in the absence of 2-mercaptoethanol to permit greater stability of the metal ions in solution. Among the divalent metal ions tested, the concentration-dependent order of inhibition of overall transcription is Pb2+ greater than Zn2+ greater than Cu2+ greater than Be2+ greater than Cd2+ greater than Ni2+ greater than Ca2+ greater than Co2+ greater than Mn2+ greater than Mg2+ greater than Sr2+ and is the same with either template. At pH 7.4 and in the absence of 2-mercaptoethanol, considerably lower concentrations of several of the divalent metal ions are needed for inhibition of overall transcription than at pH 8.1 and in the presence of 2-mercaptoethanol. Ca2+, Mg2+, Sr2+, Zn2+, Li+, Na+, and K+--considered to be non-mutagenic and non-carcinogenic--decrease chain initiation (measured with T4 DNA) at concentrations that inhibit overall transcription. Pb2+, Cd2+, Co2+, Be2+, and Mn2+--all mutagenic or carcinogenic--stimulate chain initiation (although at widely different rates) at concentrations that inhibit overall transcription. Cu2+ and Ni2+--both carcinogenic--stimulate initiation only at very low concentrations, followed by a progressive decrease in initiation at concentrations that inhibit overall transcription.
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PMID:Selective effects of metal ions on RNA synthesis rates. 617 51

The Pb2+ and Zn2+ ions are efficient catalysts for the polycytidylic acid-directed polymerization of an activated guanylic acid derivative, guanosine 5'-phosphorimidazolide. The products include oligomers of 30 to 40 units in length. The nucleotide residues are predominantly 2'-5' linked when Pb2+ is the catalyst, and predominantly 3'-5' linked in the presence of Zn2+. The significance of these results in the context of the prebiotic evolution of RNA polymerase is discussed.
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PMID:Efficient metal-ion catalyzed template-directed oligonucleotide synthesis. 624 62

Both calf and Drosophila contain a type II casein kinase with similar molecular structure and catalytic activity. Purified calf thymus casein kinase II is composed of three subunits of Mr = 44,000 (alpha), 40,000 (alpha'), and 26,000 (beta) (Dahmus, M.E. (1981) J. Biol. Chem. 256, 3319-3325), whereas the Drosophila enzyme is composed of two subunits of Mr = 36,700 (alpha) and 28,200 (beta) (Glover, C. V. C., Shelton, E. R., and Brutlag, D. L. (1983) J. Biol. Chem. 258, 3258-3265). The native form of the enzyme is an alpha 2 beta 2 tetramer. Polyclonal antibodies prepared against each enzyme react with both the alpha and beta subunits of the homologous enzyme and cross-react with both subunits of the heterologous enzyme. Reaction of polyclonal antibodies with proteins resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis establishes that no significant difference in subunit molecular weight exists between the purified enzymes and the enzyme present in initial cell extracts. Each antibody effectively inhibits the in vitro activity of the homologous enzyme and causes a slight inhibition in the activity of the heterologous enzyme. Peptide maps derived from purified subunits indicate that the alpha and beta subunits are unique and that there is extensive primary sequence homology between the corresponding subunits of the calf and Drosophila enzyme. Casein kinase II from both sources phosphorylates the same subunits of calf thymus RNA polymerase II and an identical set of proteins in a complex mixture of acid-soluble proteins from Drosophila tissue culture cells. The striking similarity in molecular structure and catalytic activity between the calf and Drosophila enzyme suggests that casein kinase II has been highly conserved in evolution.
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PMID:Similarities in structure and function of calf thymus and Drosophila casein kinase II. 658 23

The CadC protein from the cadA cadmium resistance operon of Staphylococcus aureus plasmid pI258 regulates transcription of this system in vitro. The CadC protein was overproduced in Escherichia coli cells and partially purified. Gel shift assays of the proposed cadA operator/promoter region DNA showed specific association with the CadC protein. Control arsenic resistance operator/promoter DNA from the same plasmid was not shifted by the CadC protein. Cd2+, Bi3+, and Pb2+ caused the release of CadC from DNA in gel retardation assays. DNase I footprinting measurements showed that the CadC protein specifically associated with and protected a region of operator/promoter DNA from nucleotide positions -7 to +14 relative to the start point of mRNA synthesis. Runoff transcription assays with the operator/promoter region of DNA (plus the first 69 nucleotides of the cadC gene) and purified E. coli RNA polymerase gave an mRNA product of the predicted size. Added CadC protein inhibited transcription in vitro.
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PMID:CadC, the transcriptional regulatory protein of the cadmium resistance system of Staphylococcus aureus plasmid pI258. 754 76

Humans are exposed occupationally and environmentally to metal aerosols including lead (Pb2+) and cadmium (Cd2+). These toxicants accumulate in male reproductive organs. Epidemiological studies have been equivocal about effects of Pb2+ and Cd2+ on hormone concentrations, male fertility and sperm parameters. Comparison of Pb2+ and Cd2+ concentrations in fertile and infertile men are problematic. Problem areas include failure to control confounding variables, but genetic polymorphisms as in somatic diseases may modulate Pb2+ and Cd2+ damage. Multiple calcium (Ca2+) and potassium (K+) channel isoforms have been identified in human testes and spermatozoa. These Ca2+ and K+ channels are involved in early events of acrosome reactions. Ca2+ channel are susceptible to Cd2+ poisoning and K+ channels to Pb2+. These channels offer entry paths for metallic toxicants into mature spermatozoa. Ion channel polymorphisms may cause differential sensitivities to Cd2+ and Pb2+, explaining in part prospective blinded studies showing high Cd2+ in varicocele-related human infertility and high Pb2+ in unexplained infertility. In both forms of male infertility the ability to undergo an acrosome reaction decreases. Reverse transcriptase-polymerase chain reaction assays for Ca2+ and K+ channel isoforms may identify susceptibility subgroups with lower resistance to environmental exposures.
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PMID:Male infertility and environmental exposure to lead and cadmium. 1078 69