Chiolo Irene, Saponaro Marco, Baryshnikova Anastasia, Kim Jeong-Hoon, Seo Yeon-Soo, Liberi Giordano
FIRC Institute of Molecular Oncology Foundation, Via Adamello 16, 20139 Milan, Italy.
Mol Cell Biol. 2007 Nov;27(21):7439-50. doi: 10.1128/MCB.00963-07. Epub 2007 Aug 27.
The Saccharomyces cerevisiae Srs2 UvrD DNA helicase controls genome integrity by preventing unscheduled recombination events. While Srs2 orthologues have been identified in prokaryotic and lower eukaryotic organisms, human orthologues of Srs2 have not been described so far. We found that the human F-box DNA helicase hFBH1 suppresses specific recombination defects of S. cerevisiae srs2 mutants, consistent with the finding that the helicase domain of hFBH1 is highly conserved with that of Srs2. Surprisingly, hFBH1 in the absence of SRS2 also suppresses the DNA damage sensitivity caused by inactivation of postreplication repair-dependent functions leading to PCNA ubiquitylation. The F-box domain of hFBH1, which is not present in Srs2, is crucial for hFBH1 functions in substituting for Srs2 and postreplication repair factors. Furthermore, our findings indicate that an intact F-box domain, acting as an SCF ubiquitin ligase, is required for the DNA damage-induced degradation of hFBH1 itself. Overall, our findings suggest that the hFBH1 helicase is a functional human orthologue of budding yeast Srs2 that also possesses self-regulation properties necessary to execute its recombination functions.
酿酒酵母Srs2 UvrD DNA解旋酶通过防止意外的重组事件来控制基因组完整性。虽然已在原核生物和低等真核生物中鉴定出Srs2的直系同源物,但迄今为止尚未描述Srs2的人类直系同源物。我们发现人类F-box DNA解旋酶hFBH1可抑制酿酒酵母srs2突变体的特定重组缺陷,这与hFBH1的解旋酶结构域与Srs2的高度保守这一发现一致。令人惊讶的是,在没有SRS2的情况下,hFBH1还可抑制由导致PCNA泛素化的复制后修复依赖性功能失活所引起的DNA损伤敏感性。hFBH1的F-box结构域(Srs2中不存在)对于hFBH1替代Srs2和复制后修复因子的功能至关重要。此外,我们的研究结果表明,作为SCF泛素连接酶的完整F-box结构域是DNA损伤诱导的hFBH1自身降解所必需的。总体而言,我们的研究结果表明,hFBH1解旋酶是芽殖酵母Srs2的功能性人类直系同源物,它还具有执行其重组功能所必需的自我调节特性。