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
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
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DOI：
10.1128/jb.171.5.2415-2423.1989
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发表时间：
1989-05-01
影响因子：
3.2
通讯作者：
DEVORET, R
中科院分区：
文献类型：
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作者：
DUTREIX, M;MOREAU, PL;DEVORET, R
为了分离出对recA蛋白功能有不同影响的recA突变菌株，我们在体外诱变了由mini-F质粒携带的recA基因，然后将mini-F-recA质粒导入到。delta中。对噬菌体具有溶原性的宿主。80岁，携带一个lac副本。通过对原噬菌体诱导和lac复制的重组进行评分，我们分离出了新的recA突变。发现携带突变株recA1734 （Arg-243变为Leu）的菌株缺乏.vphi。80感应，但精通重组。这种突变使得宿主即使在lexA（Def）背景下也不会被紫外线改变。然而，在引入编码UmuD* （UmuD的活性羧基末端片段）的质粒后，recA13734宿主变得可变。虽然recA1734突变允许切割。和LexA抑制因子，它使宿主缺乏。vphi的切割。80抑制因子和UmuD蛋白。另一株携带突变recA1730 （Ser-117变为Phe）的菌株被发现精通。vphi。80诱导，但缺乏重组。突变导致的重组缺陷在缺乏LexA抑制因子的细胞中得到部分缓解，这表明，当扩增时，RecA1730蛋白在重组中是活跃的。由于在recA1730菌株中，LexA蛋白被切割得很差，而噬菌体.lambda。结果表明，RecA1730蛋白不能特异性介导LexA蛋白的裂解。我们的研究结果表明，recA1734和recA1730突变对不同底物的裂解有不同的影响。recA1730突变阻止了紫外线诱变，即使在将编码UmuD*的质粒引入宿主后也是如此，并且优于recA+。相对于其他RecA函数，recA1730对RecA +是隐性的。这表明RecA蛋白除了介导LexA和UmuD蛋白的裂解外，还在诱变中起着额外的作用。
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 prohage .vphi. 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 .vphi.80 induction but proficient in recombination. The mutation rendered the host not mutable by UV, even in a lexA(Def) background. Yet, the recA13734 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 .vphi.80 repressor and UmuD protein. Another strain carrying mutation recA1730 (Ser-117 changed to Phe) was found to be proficient in .vphi. 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 besides mediating the cleavage of LexA and UmuD proteins.