Molecular and Computational Biology Program, University of Southern California, Los Angeles, CA 90089, USA.
Genetics. 2010 May;185(1):39-53. doi: 10.1534/genetics.109.112284. Epub 2010 Feb 22.
Genome stability in fission yeast requires the conserved S-phase kinase Hsk1 (Cdc7) and its partner Dfp1 (Dbf4). In addition to their established function in the initiation of DNA replication, we show that these proteins are important in maintaining genome integrity later in S phase and G2. hsk1 cells suffer increased rates of mitotic recombination and require recombination proteins for survival. Both hsk1 and dfp1 mutants are acutely sensitive to alkylation damage yet defective in induced mutagenesis. Hsk1 and Dfp1 are associated with the chromatin even after S phase, and normal response to MMS damage correlates with the maintenance of intact Dfp1 on chromatin. A screen for MMS-sensitive mutants identified a novel truncation allele, rad35 (dfp1-(1-519)), as well as alleles of other damage-associated genes. Although Hsk1-Dfp1 functions with the Swi1-Swi3 fork protection complex, it also acts independently of the FPC to promote DNA repair. We conclude that Hsk1-Dfp1 kinase functions post-initiation to maintain replication fork stability, an activity potentially mediated by the C terminus of Dfp1.
裂殖酵母的基因组稳定性需要保守的 S 期激酶 Hsk1（Cdc7）及其伴侣 Dfp1（Dbf4）。除了它们在 DNA 复制起始中的既定功能外，我们还表明这些蛋白质在 S 期和 G2 后期对于维持基因组完整性很重要。hsk1 细胞的有丝分裂重组率增加，并且需要重组蛋白才能存活。hsk1 和 dfp1 突变体对烷化剂损伤非常敏感，但在诱导诱变中却有缺陷。即使在 S 期后，Hsk1 和 Dfp1 仍与染色质相关，并且对 MMS 损伤的正常反应与染色质上完整 Dfp1 的维持相关。对 MMS 敏感突变体的筛选鉴定出了一种新型截断等位基因 rad35（dfp1-(1-519)），以及其他与损伤相关基因的等位基因。尽管 Hsk1-Dfp1 与 Swi1-Swi3 叉保护复合物一起发挥作用，但它也独立于 FPC 发挥作用，以促进 DNA 修复。我们得出结论，Hsk1-Dfp1 激酶在起始后发挥作用以维持复制叉稳定性，这种活性可能由 Dfp1 的 C 末端介导。
