酵母溴结构域蛋白Bdf1在DNA双链断裂修复中的作用与机制研究

DNA double-strand break poses a serious threat to genome stability and is closely related to human cancers. Histone acetylation plays important roles in modulating DSB repair, and this modification is primarily recognized and bound by a group of proteins harboring bromodomains. Currently, the roles of bromodomain-containing proteins in DSB repair remain largely unclear. To this end, we systematically screened this groups of proteins in Saccharomyces cerevisiae, and found that: 1) the bromodomain-containing protein Bdf1 plays a critical role in resistance to multiple DNA damaging agents; 2) Bdf1 promotes checkpoint activation and signaling induced by DSBs, and 3) Bdf1 promotes the tethering of repair proteins at breaks and facilitates DSB repair. Given that DNA repair is highly conserved in evolution, in this study, we will use budding yeast as a model to investigate the function and mechanism of Bdf1 in regulating DSB repair. Our goal is to reveal that: 1) the role and the underlying mechanism of Bdf1 in repair of DSB by homologous recombination or 2) by non-homologous end joining, and 3) the potential function of CK2-dependent Bdf1 phosphorylation in DSB repair. This study will provide deep insights into the molecular details of DSB repair and how histone acetylation may influence DSB repair, and will likely have implications in understanding how human genome stability is preserved.

DNA双链断裂(DSB)对基因组稳定性构成严重威胁，与人类癌症密切关联。组蛋白乙酰化修饰在DSB修复中起重要调控作用，该修饰主要由一类含溴结构域的蛋白进行识别。目前，该类蛋白在DSB修复中的作用仍有许多未知之处。鉴于此，我们系统筛选了酵母中含溴结构域蛋白，发现：1）溴结构域蛋白Bdf1在应对致DNA损伤药物的抗性中起重要作用；2）Bdf1促进DSB引起的检查点激活和信号转导；3）Bdf1促进修复蛋白在损伤位点募集及修复。鉴于DNA修复机制的保守性，本课题以模式生物酵母为材料，研究Bdf1在DSB修复中的作用及机制，以期阐明：1）Bdf1在同源重组中的作用及机制；2）Bdf1在非同源末端链接中的作用及机理；3）CK2依赖的Bdf1磷酸化在DSB中的潜在功能。本研究将有助于深入理解DSB修复的分子机制及组蛋白乙酰化修饰如何调控DSB修复，并为研究人类基因组稳定性提供理论借鉴。

DNA双链断裂(DSB)对基因组稳定性构成严重威胁，与人类癌症密切关联。组蛋白乙酰化修饰在DSB修复中起重要调控作用，该修饰主要由一类含溴结构域的蛋白进行识别。目前，该类蛋白在DSB修复中的作用仍有许多不清楚之处。鉴于此，我们系统筛选了酵母中含溴结构域蛋白。结合遗传学、生化及细胞生物学等多种方法与手段，我们研究发现：1）酵母溴结构域蛋白Bdf1能够促进DNA损伤应答和检查点激活；2）Bdf1通过其溴结构域促进DNA断裂末端剪切、ssDNA结合蛋白RPA和Rad51在损伤位点募集及同源重组修复；3）Bdf1通过其溴结构域结合乙酰化的组蛋白H4和 RPA，从而促进RPA的招募和重组修复；4）进一步，我们发现Bdf1的人类同源蛋白TAF1也通过其溴结构域促进DNA损伤应答、末端剪切及同源重组修复；5）TAF1通过其溴结构域结合乙酰化的H4和RPA促进RPA和RAD51募集。这样，我们揭示了Bdf1和其人类同源蛋白TAF1在同源重组中的保守功能及分子机制。此外，我们发现了泛素E3连接酶Bre1在同源重组中的功能并揭示其作用机制。我们的研究为深入阐明表观遗传修饰如何调控同源重组奠定了基础，将有利于揭示维持人类基因组稳定性的分子机制。