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New recA mutations that dissociate the various RecA protein activities in Escherichia coli provide evidence for an additional role for RecA protein in UV mutagenesis.

Abstract：

:To isolate strains with new recA mutations that differentially affect RecA protein functions, we mutagenized in vitro the recA gene carried by plasmid mini-F and then introduced the mini-F-recA plasmid into a delta recA host that was lysogenic for prophage phi 80 and carried a lac duplication. By scoring prophage induction and recombination of the lac duplication, we isolated new recA mutations. A strain carrying mutation recA1734 (Arg-243 changed to Leu) was found to be deficient in phi 80 induction but proficient in recombination. The mutation rendered the host not mutable by UV, even in a lexA(Def) background. Yet, the recA1734 host became mutable upon introduction of a plasmid encoding UmuD*, the active carboxyl-terminal fragment of UmuD. Although the recA1734 mutation permits cleavage of lambda and LexA repressors, it renders the host deficient in the cleavage of phi 80 repressor and UmuD protein. Another strain carrying mutation recA1730 (Ser-117 changed to Phe) was found to be proficient in phi 80 induction but deficient in recombination. The recombination defect conferred by the mutation was partly alleviated in a cell devoid of LexA repressor, suggesting that, when amplified, RecA1730 protein is active in recombination. Since LexA protein was poorly cleaved in the recA1730 strain while phage lambda was induced, we conclude that RecA1730 protein cannot specifically mediate LexA protein cleavage. Our results show that the recA1734 and recA1730 mutations differentially affect cleavage of various substrates. The recA1730 mutation prevented UV mutagenesis, even upon introduction into the host of a plasmid encoding UmuD* and was dominant over recA+. With respect to other RecA functions, recA1730 was recessive to recA+. This demonstrates that RecA protein has an additional role in mutagenesis beside mediating the cleavage of LexA and UmuD proteins.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Dutreix M,Moreau PL,Bailone A,Galibert F,Battista JR,Walker GC,Devoret R

doi

10.1128/jb.171.5.2415-2423.1989

subject

Has Abstract

pub_date

1989-05-01 00:00:00

pages

2415-23

issue

eissn

0021-9193

issn

1098-5530

journal_volume

171

pub_type

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New recA mutations that dissociate the various RecA protein activities in Escherichia coli provide evidence for an additional role for RecA protein in UV mutagenesis.