NATURE OF THE SOS MUTATOR ACTIVITY - GENETIC-CHARACTERIZATION OF UNTARGETED MUTAGENESIS IN ESCHERICHIA-COLI-猫眼课题宝

DOI：

10.1007/bf00339621

发表时间：

1988-08-01

期刊：

MOLECULAR AND GENERAL GENETICS

影响因子：

--

通讯作者：

中科院分区：

其他

文献类型：

--

作者：

CAILLETFAUQUET, P;MAENHAUTMICHEL, G

在大肠杆菌中，通过UV照射或通过recA基因突变诱导SOS功能促进SOS增变子活性，其在未受损的DNA中产生突变。recA 730突变对RecA蛋白的激活增加了细菌DNA中自发突变的水平。recA730诱导的突变的数量在其中复制错误未被纠正的错配修复缺陷型菌株中大大增加。这表明大多数recA730诱导的突变（90%）是通过可纠正的，即非靶向的复制错误产生的。这种recA730增变因子效应受到umuC基因突变的抑制。我们还发现，dam recA730双突变体是不稳定的，分离的克隆已经失去了dam或recA突变或已经获得了一个新的突变，可能在一个基因参与错配修复。我们认为，大坝recA730突变体的遗传不稳定性是由recA730突变引起的高水平的复制错误引起的，通过两条未甲基化的DNA链上的重合错配修复产生杀伤。recA730突变增加噬菌体的自发诱变。很糟糕recA730宿主细菌的UV照射将噬菌体非靶向诱变增加到在UV照射的recA+菌株中观察到的水平。recA730突变体中的这种UV诱导的增变因子效应不受umuC突变的抑制。因此，UV和recA730突变似乎诱导不同的SOS增变因子活性，两者都产生非靶向突变。

In Escherichia coli, induction of the SOS functions by UV irradiation or by mutation in the recA gene promotes an SOS mutator activity which generates mutations in undamaged DNA. Activation of RecA protein by the recA730 mutation increases the level of spontaneous mutation in the bacterial DNA. The number of recA730-induced mutations is greatly increased in mismatch repair deficient strains in which replication errors are not corrected. This suggests that the majority of recA730-induced mutations (90%) arise through correctable, i.e. non-targeted, replication errors. This recA730 mutator effect is suppressed by a mutation in the umuC gene. We also found that dam recA730 double mutants are unstable, segregating clones that have lost the dam or the recA mutations or that have acquired a new mutation, probably in one of the genes involved in mismatch repair. We suggest that the gentic instability of the dam recA730 mutants is provoked by the high level of replication errors induced by the recA730 mutation, generating killing by coincident mismatch repair on the two unmethylated DNA strands. The recA730 mutation increases spontaneous mutagenesis of phage .lambda. poorly. UV irradiation of recA730 host bacteria increases phage untargeted mutagenesis to the level observed in UV-irradiated recA+ strains. This UV-induced mutator effect in recA730 mutants is not suppressed by a umuC mutation. Therefore UV and the recA730 mutation seem to induce different SOS mutator activities, both generating untargeted mutations.