Yang Qin, Zhang Ran, Wang Xin W, Linke Steven P, Sengupta Sagar, Hickson Ian D, Pedrazzi Graziella, Perrera Claudia, Stagljar Igor, Littman Susan J, Modrich Paul, Harris Curtis C
Laboratory of Human Carcinogenesis, National Cancer Institute, NIH, Bldg 37, Rm 3068, 37 Convent Drive, Bethesda, MD 20892-4255, USA.
Oncogene. 2004 May 6;23(21):3749-56. doi: 10.1038/sj.onc.1207462.
The human MSH2/6 complex is essential for mismatch recognition during the repair of replication errors. Although mismatch repair components have been implicated in DNA homologous recombination repair, the exact function of hMSH2/6 in this pathway is unclear. Here, we show that the recombinant hMSH2/6 protein complex stimulated the ability of the Bloom's syndrome gene product, BLM, to process Holliday junctions in vitro, an activity that could also be regulated by p53. Consistent with these observations, hMSH6 colocalized with BLM and phospho-ser15-p53 in hydroxyurea-induced RAD51 nuclear foci that may correspond to the sites of presumed stalled DNA replication forks and more likely the resultant DNA double-stranded breaks. In addition, we show that hMSH2 and hMSH6 coimmunoprecipitated with BLM, p53, and RAD51. Both the number of RAD51 foci and the amount of the BLM-p53-RAD51 complex are increased in hMSH2- or hMSH6-deficient cells. These data suggest that hMSH2/6 formed a complex with BLM-p53-RAD51 in response to the damaged DNA forks during double-stranded break repair.
人源MSH2/6复合物对于复制错误修复过程中的错配识别至关重要。尽管错配修复成分已被认为参与DNA同源重组修复，但hMSH2/6在此途径中的具体功能尚不清楚。在此，我们表明重组hMSH2/6蛋白复合物在体外刺激了布卢姆综合征基因产物BLM处理霍利迪连接体的能力，这种活性也可由p53调节。与这些观察结果一致，hMSH6与BLM以及磷酸化丝氨酸15的p53在羟基脲诱导的RAD51核灶中共定位，这些核灶可能对应于推测的停滞DNA复制叉位点，更可能对应于由此产生的DNA双链断裂位点。此外，我们表明hMSH2和hMSH6与BLM、p53和RAD51共同免疫沉淀。在hMSH2或hMSH6缺陷细胞中，RAD51灶的数量以及BLM-p53-RAD51复合物的量均增加。这些数据表明，在双链断裂修复过程中，hMSH2/6与BLM-p53-RAD51形成复合物以应对受损的DNA叉。
