XRCC3 deficiency results in a defect in recombination and increased endoreduplication in human cells
XRCC3 deficiency results in a defect in recombination and increased endoreduplication in human cells
复制标题
DOI：
10.1038/sj.emboj.7600087
复制
发表时间：
2004-02
期刊：
影响因子：
--
通讯作者：
Takashi Yoshihara;M. Ishida;A. Kinomura;M. Katsura;Takanori Tsuruga;S. Tashiro;T. Asahara;K. Miyagawa
中科院分区：
文献类型：
--
作者：
Takashi Yoshihara;M. Ishida;A. Kinomura;M. Katsura;Takanori Tsuruga;S. Tashiro;T. Asahara;K. Miyagawa
通过基因靶向在人细胞中灭活XRCC 3。与其在同源重组中的作用一致，XRCC 3 −/−细胞对DNA交联剂的敏感性增加了一倍，姐妹染色单体交换轻度减少，Rad 51病灶形成受损，染色体畸变增加。此外，核内复制在突变体中增加了5 - 7倍。XRCC 3的T241 M变体与癌症风险增加有关。野生型cDNA的表达恢复了这种表型，而变体的表达恢复了有缺陷的重组修复，但没有增加核内复制。RPA是同源重组和DNA复制所必需的蛋白质，与XRCC 3和Rad 52相关。RPA的过表达促进了核内复制，这部分地被野生型XRCC 3蛋白的过表达所补充，但不被变体蛋白的过表达所补充。Rad 52的过表达阻止了RPA过表达细胞、XRCC 3 −/−细胞和变体表达细胞中的核内复制，这表明RPA失调是导致核内复制增加的原因。这些观察结果为同源重组和复制起始之间的关联提供了第一个遗传学证据，在癌症易感性中起作用。
XRCC3 was inactivated in human cells by gene targeting. Consistent with its role in homologous recombination,XRCC3−/−cells showed a two‐fold sensitivity to DNA cross‐linking agents, a mild reduction in sister chromatid exchange, impaired Rad51 focus formation and elevated chromosome aberrations. Furthermore, endoreduplication was increased five‐ seven‐fold in the mutants. The T241M variant of XRCC3 has been associated with an increased cancer risk. Expression of the wild‐type cDNA restored this phenotype, while expression of the variant restored the defective recombinational repair, but not the increased endoreduplication. RPA, a protein essential for homologous recombination and DNA replication, is associated with XRCC3 and Rad52. Overexpression of RPA promoted endoreduplication, which was partially complemented by overexpression of the wild‐type XRCC3 protein, but not by overexpression of the variant protein. Overexpression of Rad52 prevented endoreduplication in RPA‐overexpressing cells, inXRCC3−/−cells and in the variant‐expressing cells, suggesting that deregulated RPA was responsible for the increased endoreduplication. These observations offer the first genetic evidence for the association between homologous recombination and replication initiation having a role in cancer susceptibility.