Mankouri Hocine W, Craig Tim J, Morgan Alan
Department of Physiology, PO Box 147, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
Nucleic Acids Res. 2002 Mar 1;30(5):1103-13. doi: 10.1093/nar/30.5.1103.
Sgs1 is a member of the RecQ family of DNA helicases, which have been implicated in genomic stability, cancer and ageing. Srs2 is another DNA helicase that shares several phenotypic features with Sgs1 and double sgs1srs2 mutants have a severe synthetic growth phenotype. This suggests that there may be functional overlap between these two DNA helicases. Consistent with this idea, we found the srs2Delta mutant to have a similar genotoxin sensitivity profile and replicative lifespan to the sgs1Delta mutant. In order to directly test if Sgs1 and Srs2 are functionally interchangeable, the ability of high-copy SGS1 and SRS2 plasmids to complement the srs2Delta and sgs1Delta mutants was assessed. We report here that SGS1 is a multicopy suppressor of the methyl methanesulphonate (MMS) and hydroxyurea sensitivity of the srs2Delta mutant, whereas SRS2 overexpression had no complementing ability in the sgs1Delta mutant. Domains of Sgs1 directly required for processing MMS-induced DNA damage, most notably the helicase domain, are also required for complementation of the srs2Delta mutant. Although SGS1 overexpression was unable to rescue the shortened mean replicative lifespan of the srs2Delta mutant, maximum lifespan was significantly increased by multicopy SGS1. We conclude that Sgs1 is able to partially compensate for the loss of Srs2.
Sgs1是DNA解旋酶RecQ家族的成员，该家族与基因组稳定性、癌症和衰老有关。Srs2是另一种DNA解旋酶，与Sgs1具有若干表型特征，双突变体sgs1srs2具有严重的合成生长表型。这表明这两种DNA解旋酶之间可能存在功能重叠。与此观点一致，我们发现srs2Delta突变体与sgs1Delta突变体具有相似的基因毒素敏感性谱和复制寿命。为了直接测试Sgs1和Srs2在功能上是否可互换，评估了高拷贝SGS1和SRS2质粒对srs2Delta和sgs1Delta突变体的互补能力。我们在此报告，SGS1是srs2Delta突变体对甲磺酸甲酯（MMS）和羟基脲敏感性的多拷贝抑制因子，而SRS2过表达在sgs1Delta突变体中没有互补能力。处理MMS诱导的DNA损伤直接需要的Sgs1结构域，最显著的是解旋酶结构域，也是srs2Delta突变体互补所必需的。虽然SGS1过表达无法挽救srs2Delta突变体缩短的平均复制寿命，但多拷贝SGS1显著延长了最大寿命。我们得出结论，Sgs1能够部分补偿Srs2的缺失。
