An SOS-regulated operon involved in damage-inducible mutagenesis in Caulobacter crescentus
An SOS-regulated operon involved in damage-inducible mutagenesis in Caulobacter crescentus
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DOI：
10.1093/nar/gki551
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发表时间：
2005-01-01
影响因子：
14.9
通讯作者：
Menck, CFM
中科院分区：
文献类型：
--
作者：
Galhardo, RS;Rocha, RP;Menck, CFM
Y家族的DNA聚合酶，如大肠杆菌UmuC和DinB，是由SOS反应诱导的特异性酶，其绕过病变，允许DNA复制的继续。umuDC直向同源物在新月柄杆菌和其他细菌中不存在，提出了关于这些生物体中SOS诱变存在的问题。在这里，我们报告说，C。crescentus dinB直系同源物不参与损伤诱导的诱变。然而，由两个假设的基因和dnaE2组成的操纵子，编码Pol III催化亚基的第二个拷贝，是以recA依赖的方式损伤诱导的，并且负责大多数紫外线（UV）和丝裂霉素C诱导的C突变。crescentus。结果表明，这三个基因是DNA损伤的易错处理所必需的。这两个假设的基因在诱导突变后被命名为imuA和imuB。ImuB类似于聚合酶Y家族的蛋白质，并且可能在病变旁路中与DnaE2合作。由于imuAB dnaE2操纵子的活性而产生的突变对于UV照射是相当不寻常的，包括G：C至C：G颠换。
DNA polymerases of the Y-family, such as Escherichia coli UmuC and DinB, are specialized enzymes induced by the SOS response, which bypass lesions allowing the continuation of DNA replication. umuDC orthologs are absent in Caulobacter crescentus and other bacteria, raising the question about the existence of SOS mutagenesis in these organisms. Here, we report that the C. crescentus dinB ortholog is not involved in damage-induced mutagenesis. However, an operon composed of two hypothetical genes and dnaE2, encoding a second copy of the catalytic subunit of Pol III, is damage inducible in a recA-dependent manner, and is responsible for most ultraviolet (UV) and mitomycin C-induced mutations in C. crescentus. The results demonstrate that the three genes are required for the error-prone processing of DNA lesions. The two hypothetical genes were named imuA and imuB, after inducible mutagenesis. ImuB is similar to proteins of the Y- family of polymerases, and possibly cooperates with DnaE2 in lesion bypass. The mutations arising as a consequence of the activity of the imuAB dnaE2 operon are rather unusual for UV irradiation, including G: C to C: G transversions.