DNA解旋酶Shr1在维持异染色质稳定性中的作用

DNA damage is repaired by different mechanisms, but it is still unknown that how it is repaired under chromatin environment with specific histone modifications. DNA helicase plays important role in DNA repair and the maintenance of genome integrity. Shr1 is a DNA helicase in Schizosaccharomyces pombe that forms DNA damage-induced nuclear foci at DSB and is colocalized with Rad52, which indicates that it is involved in DNA damage repair. By synthetic genetic array screening for the enhancer of shr1 mutant, we got several heterochromatin regulators that decrease histone H3K9 methylation. The double mutants have less stable genome and more relaxed heterochromatin, but have no effect on the activation of DNA damage checkpoint. The preliminary data shows that double mutant has more unrepaired damage in heterochromatin than wild and single mutants, indicating that there are defects in heterochromatin repair. We will dissect the functions of Shr1 in DNA damage repair by molecular biological and genetic methods and elucidate how Shr1 and H3K9 methylation work together to maintain the genome stability by regulating the DNA damage repair in heterochromatin.

DNA损伤的修复过程已有较为深入的研究，但真核生物中具有不同组蛋白修饰的染色质环境下，DNA损伤修复的特异性机制还有待深入探索。DNA解旋酶在DNA损伤修复中发挥重要作用。我们从裂殖酵母突变体库中筛选DNA解旋酶Shr1缺失突变体的增强子，得到多个影响组蛋白H3第九位赖氨酸（H3K9）甲基化的异染色质调节基因突变体。Shr1与这些基因的双突变体内源DNA损伤增加、对DNA损伤试剂敏感、异染色质结构松散，但不影响DNA损伤检验点的激活，双突变体中发生在异染色质区的未修复DNA损伤明显多于野生型和单突变体，推测异染色质修复有缺陷，但机理还不清楚。在本项目中，我们将通过Shr1复合物功能和生化活性研究、全基因组分析，以及杂交和表型分析等遗传学方法，研究Shr1的功能，阐明Shr1和组蛋白H3K9甲基化是如何协同作用，通过调节异染色质区的DNA损伤修复来维持基因组稳定性的机制。