Genetic evidence for the requirement of RecA loading activity in SOS induction after UV irradiation in Escherichia coli
Genetic evidence for the requirement of RecA loading activity in SOS induction after UV irradiation in Escherichia coli
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DOI：
10.1128/jb.00130-06
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发表时间：
2006-07-01
影响因子：
3.2
通讯作者：
Brcic-Kostic, Krunoslav
中科院分区：
文献类型：
--
作者：
Ivancic-Bace, Ivana;Vlasic, Ignacija;Brcic-Kostic, Krunoslav
在大肠杆菌中的SOS反应导致40多个基因的协同诱导表达，这发生在细胞被DNA损伤剂处理时。这种反应依赖于RecA(辅酶)、LexA(抑制子)和单链DNA(SsDNA)的存在。SOS诱导的先决条件是形成RecA-ssDNA细丝。根据DNA底物的不同，RecA-ssDNA细丝可以通过RecBCD、RecFOR或具有特定酶活性的混合重组机制产生，包括解旋酶、核酸外切酶和RecA负载。在这项研究中，我们研究了RecA负载活性在紫外线照射后SOS诱导中的作用。我们在带有RecBCD酶(recB1080等位基因)RecA加载活性突变的菌株中进行了SOS诱导的遗传分析。我们发现RecA的负载活性对于SOS的诱导是必不可少的。在recB1080中，突变的RecQ解旋酶并不重要，而RecJ核酸酶则略微降低了LJV照射后SOS的诱导。此外，我们还发现，recB1080突变体表现出SOS调节子的结构性表达。令人惊讶的是，这种结构性SOS表达依赖于RecJ蛋白，而不依赖于RecFOR，这意味着存在不同的RecA负载机制来表达结构性SOS。
The SOS response in Escherichia coli results in the coordinately induced expression of more than 40 genes which occurs when cells are treated with DNA-damaging agents. This response is dependent on RecA (coprotease), LexA (repressor), and the presence of single-stranded DNA (ssDNA). A prerequisite for SOS induction is the formation of a RecA-ssDNA filament. Depending on the DNA substrate, the RecA-ssDNA filament is produced by either RecBCD, RecFOR, or a hybrid recombination mechansim with specific enzyme activities, including helicase, exonuclease, and RecA loading. In this study we examined the role of RecA loading activity in SOS induction after UV irradiation. We performed a genetic analysis of SOS induction in strains with a mutation which eliminates RecA loading activity in the RecBCD enzyme (recB1080 allele). We found that RecA loading activity is essential for SOS induction. In the recB1080 mutant RecQ helicase is not important, whereas RecJ nuclease slightly decreases SOS induction after LJV irradiation. In addition, we found that the recB1080 mutant exhibited constitutive expression of the SOS regulon. Surprisingly, this constitutive SOS expression was dependent on the Recj protein but not on RecFOR, implying that there is a different mechanism of RecA loading for constitutive SOS expression.