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)

Restriction endonuclease Bgl II cleaves T7 DNA at a unique site (28.76% on the standard T7 map), yielding two fragments of molecular weights 18.9 x 10(6) (A) and 7.6 x 10(6) (B). Fragment B, representing the leftmost portion of the genome, has been purified by zone sedimentation. Transcription of fragment B by T7-specific RNA polymerase gives only r-strand-specific RNA. Analysis of the products by polyacrylamide gel electrophoresis reveals four major RNA species which have apparent molecular weights of 2.1 x 10(6), 1.36 x 10(6), 0.85 x 10(6) and 0.125 x 10(6), respectively. Each of these RNAs is reduced in size when transcription is carried out with fragment B, which has been shortened by treatment with Escherichia coli exonuclease III. Therefore, each of the transcripts must be terminated at the right end of fragment B. Analysis of the molecular weights of the four transcripts produced from whole and from exonucleolytically shortened fragment B suggests that these transcripts are read from promoters located at 13.5, 18.9, 22.6, and 27.9%, respectively, on the standard T7 map. Hence, there are at least four promoters governing the transcription of the class II region. Transcripts initiated at these promoters on intact T7 DNA appear to read through the class II and part of the class III genetic region and terminate at the strong terminator for T7-specific RNA polymerase near 61%. Transcription of fragment B which has been cleaved with the restriction endonuclease Hpa I seems to activate a fifth promoter for T7-specific RNA polymerase. This promoter appears to be identical to the promoter previously described by Oakley and Coleman (Proc. Natl. Acad. Sci. U.S.A. 74:4266-4270, 1977) that maps near 15% on the standard T7 map. Little or no RNA is read from T7 Bgl II fragment B, which has a mobility expected for a transcript read from this promoter. However, upon cleavage with Hpa I, this promoter is utilized approximately 10-fold more efficiently than the other class II promoters. The mechanism of this activation is not yet known.
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PMID:Mapping of class II promoter sites utilized in vitro by T7-specific RNA polymerase on bacteriophage T7 DNA. 43 May 92

We have developed a novel technique to map restriction sites on large duplex DNAs by electron microscopy. In this method, the sample DNA is first cut with a restriction enzyme. The resulting fragments are briefly digested with Escherichia coli exonuclease III, and treated with wheat germ RNA polymerase II to fill-in with RNA the resulting gaps. These small RNAs, complementary to sequences immediately adjacent to either side of the restriction site, are isolated from the DNA template and R-looped to the full-length DNA. When this material is prepared by the formamide-cytochrome spreading technique, small bubbles are visible wherever there is a restriction site on the DNA. Improved methods of mapping are outlined.
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PMID:Mapping restriction sites on large DNAs by electron microscopy. 631 36

Drosophila Rrp1 protein has four tightly associated enzymatic activities: DNA strand transfer, ssDNA renaturation, dsDNA 3'-exonuclease and apurinic/apyrimidinic (AP) endonuclease. The carboxy-terminal region of Rrp1 is homologous to Escherichia coli exonuclease III and several eukaryotic AP endonucleases. All members of this protein family cleave abasic sites. Rrp1 protein was expressed under the control of the E. coli RNA polymerase tac promoter (pRrp1-tac) in two repair deficient E. coli strains (BW528 and LG101) lacking both exonuclease III (xth) and endonuclease IV (nfo). Rrp1 confers resistance to killing by oxidative, antitumor and alkylating agents that damage DNA (hydrogen peroxide, t-butylhydroperoxide, bleomycin, methyl methanesulfonate, and mitomycin C). Complementation of the repair deficiency by Rrp1 provides up to a two log increase in survival and requires the C-terminal nuclease region of Rrp1, but not its N-terminal region. The AP endonuclease activity in extracts from the repair deficient strain LG101 is increased up to 12-fold when the strain contains pRrp1-tac. These results indicate that pRrp1-tac directs the synthesis of active enzyme, and that the nuclease activities of Rrp1 are likely to be the cause of the increased resistance to DNA damage of the mutant cells.
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PMID:Drosophila Rrp1 complements E. coli xth nfo mutants: protection against both oxidative and alkylation-induced DNA damage. 769 34