Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
DNA Repair (Amst). 2010 Nov 10;9(11):1151-61. doi: 10.1016/j.dnarep.2010.08.003.
Deinococcus radiodurans is one of the most radiation-resistant organisms known. It can repair hundreds of radiation-induced double-strand DNA breaks without loss of viability. Genome reassembly in heavily irradiated D. radiodurans is considered to be an error-free process since no genome rearrangements were detected after post-irradiation repair. Here, we describe for the first time conditions that frequently cause erroneous chromosomal assemblies. Gross chromosomal rearrangements have been detected in recA mutant cells that survived exposure to 5kGy γ-radiation. The recA mutants are prone also to spontaneous DNA rearrangements during normal exponential growth. Some insertion sequences have been identified as dispersed genomic homology blocks that can mediate DNA rearrangements. Whereas the wild-type D. radiodurans appears to repair accurately its genome shattered by 5kGy γ-radiation, extremely high γ-doses, e.g., 25kGy, produce frequent genome rearrangements among survivors. Our results show that the RecA protein is quintessential for the fidelity of repair of both spontaneous and γ-radiation-induced DNA breaks and, consequently, for genome stability in D. radiodurans. The mechanisms of decreased genome stability in the absence of RecA are discussed.
耐辐射球菌是已知的抗辐射能力最强的生物之一。它可以在不丧失生存能力的情况下修复数百个由辐射引起的双链 DNA 断裂。在重辐射的耐辐射球菌中，基因组的重新组装被认为是一个无错误的过程，因为在辐照后修复后没有检测到基因组重排。在这里，我们首次描述了经常导致错误染色体组装的条件。在幸存于 5kGy γ 辐射的 recA 突变细胞中检测到了严重的染色体重排。recA 突变体在正常指数生长过程中也容易发生自发的 DNA 重排。一些插入序列已被鉴定为分散的基因组同源性块，可介导 DNA 重排。虽然野生型耐辐射球菌似乎能准确修复其被 5kGy γ 辐射破碎的基因组，但极高的 γ 剂量，例如 25kGy，会导致幸存者中频繁发生基因组重排。我们的结果表明，RecA 蛋白对于修复自发和 γ 辐射诱导的 DNA 断裂的准确性以及耐辐射球菌基因组的稳定性至关重要。讨论了在缺乏 RecA 的情况下基因组稳定性降低的机制。
