Cell cycle and genetic requirements of two pathways of nonhomologous end-joining repair of double-strand breaks in Saccharomyces cerevisiae
Cell cycle and genetic requirements of two pathways of nonhomologous end-joining repair of double-strand breaks in Saccharomyces cerevisiae
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DOI：
10.1128/mcb.16.5.2164
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发表时间：
1996-05-01
影响因子：
5.3
通讯作者：
Haber, JE
中科院分区：
文献类型：
--
作者：
Moore, JK;Haber, JE
在酿酒酵母中，HO核酸内切酶诱导的双链断裂可以通过至少两种与哺乳动物细胞中的事件非常相似的非同源末端连接（NHEJ）途径来修复。在一种途径中，染色体末端被降解以产生具有不同大小的缺失，其末端具有1至6 bp的同源性。（5 ′-AACA-3 ′）不被降解，但可以在错配中碱基配对以产生+CA和+ACA插入。当HO在整个细胞周期中表达时，NHEJ的修复效率比仅在G（1）中表达HO时高30倍。当HO在整个细胞周期中表达时，修复事件的类型也非常不同; 78%的存活者有小的插入，而几乎没有大的缺失。当HO表达局限于G1期时，只有21%是插入，38%有大的缺失，这些结果表明，有不同的机制，NHEJ修复产生插入或缺失，这两个途径受到不同的影响到HO表达的细胞周期中的时间，NHEJ的频率在缺失了RLDI、RAD 2、RAD 51、RAD 52、RAD 54或RAD 57的菌株中没有改变;然而，当HO不受细胞周期调节时，RAD 50、XRS 2或MRE 11的缺失使NHEJ减少超过70倍。此外，这三个基因中的突变显著减少+CA插入，同时显著增加了小（-ACA）和大缺失事件的比例。相反，rad 50突变对G（1）诱导的细胞的存活率几乎没有影响，但显著降低了+CA插入和-ACA缺失的频率，有利于更大的缺失。RAD 50（以及扩展XRS 2和MRE 11）在S和/或G（2）中发现的NHEJ修复的插入产生途径中发挥的作用比在HO仅在G（1）中表达时占主导地位的较不常见的缺失事件中发挥的作用重要得多。
In Saccharomyces cerevisiae, an HO endonuclease-induced double-strand break can be repaired by at least two pathways of nonhomologous end joining (NHEJ) that closely resemble events in mammalian cells. In one pathway the chromosome ends are degraded to yield deletions with different sizes whose endpoints have 1 to 6 bp of homology, Alternatively, the 4-bp overhanging 3' ends of HO-cut DNA (5'-AACA-3') are not degraded but can be base paired in misalignment to produce +CA and +ACA insertions, When HO was expressed throughout the cell cycle, the efficiency of NHEJ repair was 30 times higher than when HO was expressed only in G(1). The types of repair events were also very different when HO was expressed throughout the cell cycle; 78% of survivors had small insertions, while almost none had large deletions, When HO expression was confined to the G, phase, only 21% were insertions and 38% had large deletions, These results suggest that there are distinct mechanisms of NHEJ repair producing either insertions or deletions and that these two pathways are differently affected by the time in the cell cycle when HO is expressed, The frequency of NHEJ is unaltered in strains from which R LDI, RAD2, RAD51, RAD52, RAD54, or RAD57 is deleted; however, deletions of RAD50, XRS2, or MRE11 reduced NHEJ by more than 70-fold when HO was not cell cycle regulated, Moreover, mutations in these three genes markedly reduced +CA insertions, while significantly increasing the proportion of both small (-ACA) and larger deletion events, In contrast, the rad50 mutation had little effect on the viability of G(1)-induced cells but significantly reduced the frequency of both +CA insertions and -ACA deletions in favor of larger deletions, Thus, RAD50 (and by extension XRS2 and MRE11) exerts a much more important role in the insertion-producing pathway of NHEJ repair found in S and/or G(2) than in the less frequent deletion events that predominate when HO is expressed only in G(1).