Ultraviolet-Sensitive Mutator mutU4 of Escherichia coli Inviable with polA

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The Escherichia coli mutator genes mutU4, mutS3, and mut-25 (a possible allele of mutL), previously known to induce transitional base changes, increased significantly the frequencies of reversion of lacZ frameshift mutations. mutTI, previously shown to induce only the transversion of adenine-thymine to cytosine-guanine, had no effect on the reversion of lacZ frameshift mutations. With mutator genes other than mutTi, small increases were found in the frequencies of reversion of trpA frameshift mutations. 994 on July 31, 2020 by guest

Section: Discussionmentioning

confidence: 99%

Reversion of Frameshift Mutations by Mutator Genes in Escherichia coli

Siegel

Kamel

1974

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“…The search for lethal mutant combinations like those involving rho-15 provides a straightforward genetic approach for revealing the existence of functional relationships between proteins without first requiring a detailed biochemical understanding of the functions. If we include the lethal pair polA uvrD (29,31) with the mutant combinations uvrD rep, rep ssb, rep rho, ssb rho, and rho rpoB, then we have six proteins involved in the replication and transcription of DNA that are linked by a chain of genetic evidence suggesting intricate interrelationships among these proteins which remain to be explored biochemically.…”

Section: Resultsmentioning

confidence: 99%

Lethality of the double mutations rho rep and rho ssb in Escherichia coli

Fassler¹,

Tessman²,

Tessman³

1985

The similarity of rho mutants to rep and ssb mutants in sensitivity to UV light and in recombination deficiency suggested that the function of the Rho protein might be related to that of Rep and Ssb. In support of that idea, we found that rho rep and rho ssb double mutants are either nonviable, or at best only marginally viable. Viability could be restored by suppressor mutations, one of which mapped either in the rho gene or close to its 5'-end. Rho may thus share a role with Rep and Ssb in replication and the structural maintenance of DNA; a multifunctional Rho protein could account for the diversity of the defects seen in rho mutants, some of which appear to have no relation to the defect in transcription termination.

“…One difference between the recL and uvrD gene products may reside in the resynthesis step of the excision repair process. This is of special interest in view of the numerous suggestions (12,16,18,21,25,26,35,37,39,42) that mutations in the uvrD cistron are closely involved with maintaining full function of DNA polymerase I. The notion that these mutations are involved with the resynthesis step of excision repair is partly due to extrapolation from phenotypic imilarities with polA mutants (26) and from the observation that at the restrictive temperature combinations of polA12 (temperature sensitive for DNA polymerase I) with mutations in the uvrD cistron are inviable (16).…”

Section: Resultsmentioning

confidence: 99%

“…The notion that these mutations are involved with the resynthesis step of excision repair is partly due to extrapolation from phenotypic imilarities with polA mutants (26) and from the observation that at the restrictive temperature combinations of polA12 (temperature sensitive for DNA polymerase I) with mutations in the uvrD cistron are inviable (16). The mutator phenotype of uvrE (16,34,37) and its inviability in combination withpolA (16,18,35) are compatible with an involvement with DNA synthesis. The speculation that incision breaks in uvrE strains lack a 3'-OH terminus suitable for DNA polymerase I has also been offered (39).…”

Section: Resultsmentioning

confidence: 99%

Effect of the uvrD mutation on excision repair

Kuemmerle¹,

Masker²

1980

A pair of related Escherichia coli K-12 strains, one of which contains the uvrD101 mutation, were constructed and compared for ability to perform various steps in the excision repair of deoxyribonucleic acid damage inflicted by ultraviolet radiation. The results of this study indicated: (i) ultraviolet sensitivity in the uvrD101 mutant was greater than that of wild type but less than that measured in an incision-deficient uvrA mutant; (ii) host cell reactivation paralleled the survival data; (iii) postirradiation deoxyribonucleic acid degradation was virtually identical in the two strains; (iv) incision, presumably at the sites of pyrimidine dimers, proceeded normally in the uvrD101 strain; (v) excision of pyrimidine dimers was markedly reduced in both rate and extent in the uvrD101 mutant; (vi) the amount of repair resynthesis was the same in both strains, and there was no evidence of abnormally long repair patches in the uvrD mutant; and (vii) rejoining of incision breaks was slow and incomplete in the uvrD strain. These data suggest that the ultraviolet sensitivity conferred by the uvrD mutation arises from inefficient removal of pyrimidine dimers or from failure to close incision breaks. The data are compatible with the notion that the uvrD+ gene produce affects the conformation of incised deoxyribonucleic acid molecules.