Lawrence Katherine S, Chau Thinh, Engebrecht JoAnne
Department of Molecular and Cellular Biology; Biochemistry, Molecular Cellular and Developmental Biology Graduate Group, University of California, Davis, Davis, California, United States of America.
PLoS Genet. 2015 Apr 21;11(4):e1005150. doi: 10.1371/journal.pgen.1005150. eCollection 2015 Apr.
Errors in replication or segregation lead to DNA damage, mutations, and aneuploidies. Consequently, cells monitor these events and delay progression through the cell cycle so repair precedes division. The DNA damage response (DDR), which monitors DNA integrity, and the spindle assembly checkpoint (SAC), which responds to defects in spindle attachment/tension during metaphase of mitosis and meiosis, are critical for preventing genome instability. Here we show that the DDR and SAC function together throughout the cell cycle to ensure genome integrity in C. elegans germ cells. Metaphase defects result in enrichment of SAC and DDR components to chromatin, and both SAC and DDR are required for metaphase delays. During persistent metaphase arrest following establishment of bi-oriented chromosomes, stability of the metaphase plate is compromised in the absence of DDR kinases ATR or CHK1 or SAC components, MAD1/MAD2, suggesting SAC functions in metaphase beyond its interactions with APC activator CDC20. In response to DNA damage, MAD2 and the histone variant CENPA become enriched at the nuclear periphery in a DDR-dependent manner. Further, depletion of either MAD1 or CENPA results in loss of peripherally associated damaged DNA. In contrast to a SAC-insensitive CDC20 mutant, germ cells deficient for SAC or CENPA cannot efficiently repair DNA damage, suggesting that SAC mediates DNA repair through CENPA interactions with the nuclear periphery. We also show that replication perturbations result in relocalization of MAD1/MAD2 in human cells, suggesting that the role of SAC in DNA repair is conserved.
复制或分离错误会导致DNA损伤、突变和非整倍体。因此，细胞会监测这些事件并延迟细胞周期进程，以便在分裂之前进行修复。监测DNA完整性的DNA损伤反应（DDR）以及在有丝分裂和减数分裂中期对纺锤体附着/张力缺陷作出反应的纺锤体组装检查点（SAC），对于防止基因组不稳定至关重要。在这里，我们表明DDR和SAC在整个细胞周期中共同发挥作用，以确保秀丽隐杆线虫生殖细胞中的基因组完整性。中期缺陷导致SAC和DDR成分富集到染色质上，并且中期延迟需要SAC和DDR两者。在双定向染色体建立后持续的中期停滞期间，在没有DDR激酶ATR或CHK1或SAC成分MAD1/MAD2的情况下，中期板的稳定性受到损害，这表明SAC在中期的功能超出了其与APC激活剂CDC20的相互作用。响应DNA损伤，MAD2和组蛋白变体CENPA以DDR依赖的方式在核周边富集。此外，MAD1或CENPA的缺失会导致周边相关的受损DNA丢失。与对SAC不敏感的CDC20突变体相反，缺乏SAC或CENPA的生殖细胞不能有效地修复DNA损伤，这表明SAC通过CENPA与核周边的相互作用介导DNA修复。我们还表明，复制扰动会导致人细胞中MAD1/MAD2重新定位，这表明SAC在DNA修复中的作用是保守的。
