Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The induction of prophage lambda by ultraviolet light has been measured in E. coli K12 lysogenic cells deficient in DNA polymerase I. The efficiency of the induction process was greater in polA1 polC(dnaE) double mutants incubated at the temperature that blocks DNA replication than in polA+ polC single mutants. Similarly, the polA1 mutation sensitized tif-promoted lysogenic induction in a polA1 tif strain at 42 degrees. In strains bearing the polA12 mutation, which growth normally at 30 degrees, induction of the prophage occurred after the shift to 42 degrees. It is concluded that dissapearance of the DNA polymerase I activity leads to changes in DNA replication that are able, per se, trigger the prophage induction process.
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PMID:Prophage induction in Escherichia coli K12 cells deficient in DNA polymerase I. 33 8

The RecA protein of Escherichia coli is required for SOS-induced mutagenesis in addition to its recombinational and regulatory roles. We have suggested that RecA might participate directly in targeted mutagenesis by binding preferentially to the site of the DNA damage (e.g. pyrimidine dimer) because of its partially unwound nature; DNA polymerase III will then encounter RecA-coated DNA at the lesion and might replicate across the damaged site more often but with reduced fidelity. In support of this proposal, we have found that the phenotype of wild-type and mutant RecA for mutagenesis correlates with capacity to bind to double-stranded DNA. Wild-type RecA binds more efficiently to ultraviolet (u.v.)-irradiated, duplex DNA than to non-irradiated DNA. The RecA441 (Tif) protein that is constitutive for mutagenesis binds extremely well to double-stranded DNA with no lesions, whereas the RecA430 protein that is defective in mutagenesis binds poorly even to u.v.-irradiated DNA. The RecA phenotype also correlates with capacity to use duplex DNA as a cofactor for cleavage of the LexA repressor protein for SOS-controlled operons. Wild-type RecA provides efficient cleavage of LexA only with u.v.-irradiated duplex DNA; RecA441 cleaves well with non-irradiated DNA; RecA430 gives very poor cleavage even with u.v.-irradiated DNA. We conclude that the interaction of RecA with damaged double-stranded DNA is likely to be a critical component of SOS mutagenesis and to define a pathway for the LexA cleavage reaction as well.
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PMID:RecA protein and SOS. Correlation of mutagenesis phenotype with binding of mutant RecA proteins to duplex DNA and LexA cleavage. 296 Aug 17

The dnaQ (mutD) gene product which encodes the epsilon-subunit of the DNA polymerase III holoenzyme has a central role in controlling the fidelity of DNA replication because both mutD5 and dnaQ49 mutations severely decrease the 3'-5' exonucleolytic editing capacity. It is shown in this paper that more than 95% of all dnaQ49-induced base pair substitutions are transversions of the types G:C-T:A and A:T-T:A. Not only is this unusual mutational specificity precisely that observed recently for a number of potent carcinogens such as benzo(a) pyrene diolepoxide (BPDE) and aflatoxin B1 (AFB1), which are dependent on the SOS system to mutagenize bacteria, but it is also seen for the constitutively expressed SOS mutator activity in E. coli tif-1 strains as well as for the SOS mutator activity mediated gap filling of apurinic sites. Because the G:C-T:A and A:T-T:A transversions can either result from the insertion of an adenine across from apurinic sites or arise due to the incorporation of syn-adenine opposite a purine base, we postulate that the DNA polymerase III holoenzyme also has a reduced discrimination ability in a dnaQ49 background. The introduction of a lexA (Ind-) allele, which prevents the expression of SOS functions, led to a significant reduction in the dnaQ49-caused mutator effect. Both, the mutational specificity observed and the partial lexA+ dependence of the mutator effect provoke a reanalysis of the hypothesis that the DNA polymerase III holoenzyme can be converted into the postulated but until now unidentified SOS polymerase.
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PMID:Mutational specificity of a proof-reading defective Escherichia coli dnaQ49 mutator. 351 28

A novel form of DNA polymerase I (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, DNA nucleotidyltransferase, EC 2.7.7.7) activity has been isolated from Escherichia coli cells that had been activated for expression of the DNA damage-inducible genes. Induction was by treatment of normal cells or cells carrying the spr-51 and tif-1 mutations with nalidixic acid. This activity, DNA polymerase I, seems to be a form of DNA polymerase I because it is insensitive to N-ethylmaleimide, is inhibited by antibody to DNA polymerase I, and does not appear in a polA1 strain. DNA polymerase I activity sediments through sucrose gradients as a broad peak with s20.w = 6.6--10.5, compared with an s20,w = 4.8--5.5 for DNA polymerase I. The fidelity during polymerization reactions of DNA polymerase I is relatively low with a variety of synthetic templates and deoxynucleoside triphosphates, although the enzyme appears to have a normal level of 3' greater than 5' exonuclease. Polymerase I has properties that might implicate it in some form of mutagenic DNA repair.
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PMID:Isolation of an altered form of DNA polymerase I from Escherichia coli cells induced for recA/lexA functions. 628 65