Regulation of SOS mutagenesis by proteolysis
Regulation of SOS mutagenesis by proteolysis
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DOI：
10.1073/pnas.93.19.10291
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发表时间：
1996-09-17
影响因子：
11.1
通讯作者：
Woodgate, R
中科院分区：
文献类型：
--
作者：
Frank, EG;Ennis, DG;Woodgate, R
大肠杆菌中的DNA损伤诱导突变在很大程度上取决于UmuD（UmuD '）和UmuC蛋白的活性。这些蛋白质的细胞内水平在转录和翻译后水平都受到严格调控。这样的调节可能允许细胞在进入易错途径之前通过无错修复途径处理DNA损伤。我们最近发现，作为这种精心调控的一部分，UmuD和UmuC蛋白在体内迅速降解。我们在这里报告，负责其降解的酶是ATP依赖性丝氨酸蛋白酶，Lon。相比之下，UmuD'（UmuD的翻译后产物和诱变活性形式）被Lon以低得多的速率降解，但被另一种ATP依赖性蛋白酶ClpXP快速降解。有趣的是，只有当ClpXP与UmuD形成异二聚体复合物时，UmuD'才被ClpXP快速降解。UmnD/UmuD'异二聚体的形成优先于UmuD'同二聚体，因此靶向UmuD'蛋白进行蛋白水解。这种机制允许细胞降低致突变活性Umu蛋白的细胞内水平，从而一旦发生易错DNA修复，就返回到静息状态。异二聚体UmuD/D'复合物的表观半衰期在clpX：：Kan和clpP：：Kan菌株中大大增加，并且相应地使这些菌株实际上是UV不可突变的。我们认为这些表型与以下建议一致，即虽然UmuD/D'异二聚体是无诱变活性的，但它仍然保留与UmuC相互作用的能力，从而排除了诱变活性UmuD' C-2复合物的形成。
DNA damage-inducible mutagenesis in Escherichia coli is largely dependent upon the activity of the UmuD (UmuD') and UmuC proteins. The intracellular level of these proteins is tightly regulated at both the transcriptional and the posttranslational levels. Such regulation presumably allows cells to deal with DNA damage via error-free repair pathways before being committed to error-prone pathways. We have recently discovered that as part of this elaborate regulation, both the UmuD and the UmuC proteins are rapidly degraded in vivo. We report here that the enzyme responsible for their degradation is the ATP-dependent serine protease, Lon. In contrast, UmuD' (the posttranslational product and mutagenically active form of UmuD) is degraded at a much reduced rate by Lon, but is instead rapidly degraded by another ATP-dependent protease, ClpXP. Interestingly, UmuD' is rapidly degraded by ClpXP only when it is in a heterodimeric complex with UmuD. Formation of UmnD/UmuD' heterodimers in preference to UmuD' homodimers therefore targets UmuD' protein for proteolysis. Such a mechanism allows cells to reduce the intracellular levels of the mutagenically active Umu proteins and thereby return to a resting state once error-prone DNA repair has occurred. The apparent half-life of the heterodimeric UmuD/D' complex is greatly increased in the clpX::Kan and clpP::Kan strains and these strains are correspondingly rendered virtually UV non-mutable. We believe that these phenotypes are consistent with the suggestion that while the UmuD/D' heterodimer is mutagenically inactive, it still retains the ability to interact with UmuC, and thereby precludes the formation of the mutagenically active UmuD'C-2 complex.