Roles of SGS1, MUS81, and RAD51 in the repair of lagging-strand replication defects in Saccharomyces cerevisiae
Roles of SGS1, MUS81, and RAD51 in the repair of lagging-strand replication defects in Saccharomyces cerevisiae
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DOI：
10.1007/s00294-005-0014-5
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发表时间：
2005-10-01
期刊：
影响因子：
2.5
通讯作者：
Brill, SJ
中科院分区：
文献类型：
--
作者：
Ii, M;Brill, SJ
缺乏 SGS1 DNA 解旋酶和 MUS81 结构特异性核酸内切酶的酵母细胞表现出合成致死性，这种致死性会因 RAD51 重组酶的缺失而受到抑制。这种上位相互作用表明 SGS1 或 MUS81 或这两个基因的主要功能位于 RAD51 的下游。为了鉴定 SGS1 和 MUS81 的 RAD51 独立功能，对 sgs1 mus81 rad51 三重突变体进行了合成致死筛选。我们发现，编码异源三聚体 RNase H2 亚基的 RNH202 突变在这种背景下产生了严重的合成疾病。 RNase H2 被认为在冈崎片段成熟中起非必需作用。当单独与 mus81 或 sgs1 结合时，缺乏 RNH202 的细胞表现出合成生长缺陷。但是，虽然RAD51的缺失对rnh202 sgs1双突变体影响不大，但它强烈抑制了rnh202 mus81细胞的生长。这些数据表明，SGS1（而非 MUS81）的主要功能是 RAD51 的下游。然而，SGS1 必须具有一些独立于 RAD51 的功能，因为 rnh202 mus81 rad51 细胞的生长因 SGS1 的缺失而进一步受到损害。与这些结果一致，我们表明 rnh202 细胞表现出对 DNA 损伤剂的敏感性，在 RAD51 或 MUS81 不存在的情况下这种敏感性会加剧。这些数据支持一个模型，其中滞后链复制中的缺陷由 Mus81 核酸内切酶或通过依赖于 Rad51 和 Sgs1 的途径修复。
Yeast cells lacking the SGS1 DNA helicase and the MUS81 structure-specific endonuclease display a synthetic lethality that is suppressed by loss of the RAD51 recombinase. This epistatic interaction suggests that the primary function of SGS1 or MUS81, or both genes, is downstream of RAD51. To identify RAD51-independent functions of SGS1 and MUS81, a synthetic-lethal screen was performed on the sgs1 mus81 rad51triple mutant. We found that mutation of RNH202, which encodes a subunit of the hetero-trimeric RNase H2, generates a profound synthetic-sickness in this background. RNase H2 is thought to play a non-essential role in Okazaki fragment maturation. Cells lacking RNH202 showed synthetic growth defects when combined with either mus81 or sgs1 alone. But, whereas the loss of RAD51 had little effect on rnh202 sgs1 double mutants, it strongly inhibited the growth of rnh202 mus81 cells. These data indicate that the primary function of SGS1, but not MUS81, is downstream of RAD51. SGS1 must have some RAD51-independent function, however, since the growth of rnh202 mus81 rad51cells was further compromised by the loss of SGS1. Consistent with these results, we show that rnh202 cells display a sensitivity to DNA-damaging agents that is exacerbated in the absence of RAD51 or MUS81. These data support a model in which defects in lagging-strand replication are repaired by the Mus81 endonuclease or through a pathway dependent on Rad51 and Sgs1.