半胱氨酸富含蛋白CCN1调控同源重组修复的分子机制及在乳腺癌放化疗中的功能研究

DNA损伤应答对于真核生物维持基因组的稳定性十分重要，ATM作为DNA损伤通路中的重要激酶，在损伤应答过程中发挥中枢调控作用，然而其作用机制仍不十分明确。在前期研究中，我们发现：在DNA损伤情况下， CCN1第237位丝氨酸发生显著磷酸化修饰，抑制ATM的活性显著降低其磷酸化水平，提示CCN1可能是ATM激酶新的作用底物；进一步又发现CCN1促进同源重组修复(HR)过程，而对非同源末端连接修复(NHEJ)没有影响，提示CCN1新的功能是促进同源重组修复；机制上发现CCN1通过促进末端切割蛋白CtIP的募集到DNA断裂处，发起DNA末端切割过程。本项目将深入研究ATM磷酸化CCN1促进募集CtIP蛋白参与同源重组修复的分子机制，通过体内与体外实验探讨ATM-CCN1-CtIP通路在乳腺癌中的功能，并检测CCN1与放化疗及PARP1抑制剂敏感性的关系，为乳腺癌的诊断与靶向治疗提供新的思路。

The DNA damage response signaling is critical for the maintenance of organism genome integrity. During the process of DNA damage, ATM kinase plays a pivotal role in DNA damage pathway. However, how this process occurs within the context of chromatin is still not well understood. Using ATM/ATR substrate antibody, we have found that CCN family protein CCN1 is a direct subtrate of ATM. In response to DNA damage, ATM phosphorylates CCN1 at serine 237 to recruit it to DNA double-strand break(DSB) sites. Further more, we also observed that the depletion of CCN1 resulted in defective HR repair efficiency; however, we observed no different in NHEJ frequency upon CCN1 depletion. These findings suggest that CCN1 promotes DSB repair by HR. Moreover, we reveal that CCN1 forms a complex with CtIP and promotes accumulation of CtIP at DSBs.Taken together, our aims of this study are further clarifying the molecular mechanism and significance of CCN1-mediated regulation of HR repair in response to DNA damage, and providing strong theoretical basis for reasonable selection of PARP inhibitors in breast cancer therapy.