小蛋白Meteor在DNA双链断裂损伤修复中的作用机制

基因组DNA不断受到细胞内外源的攻击而造成损伤,其中以双链断裂(DSB)最为严重。DSB可激活DNA损伤检验点,启动非同源末端连接(NHEJ)或同源重组(HR)等方式修复。当姐妹染色单体存在时,DSB会诱导两者的黏连,但具体机制在动物细胞中尚不明确,其在DSB修复通路选择中的作用也未明了。在与黏连因子Sororin的互作蛋白中,我们鉴定到一个小蛋白,因其在DSB位点快速聚集快速消失的特征,将其命名为Meteor。敲低Meteor导致HR频率降低、NHEJ修复增加。本立项将在此基础上,结合哺乳动物细胞系和小鼠模型,探究Meteor在损伤诱导的姐妹染色单体黏连及修复途径选择中的作用机制,阐述其异常表达在相关组织癌症发生发展中的作用,从而揭示小蛋白这类细胞内的“暗物质”在基因组稳定性中的重要作用,为癌症诊断和治疗新型靶标的研发提供理论依据。

The genome DNA is frequently attacked by both endogenous and exogenous stimuli, leading to various types of DNA lesions. Among them, DNA double-strand breaks (DSBs) are the most severe ones. DSBs activate the DNA damage checkpoint that triggers the downstream repair pathways, most frequently the non-homologous end joining (NHEJ) or homologous recombination (HR) repair. When sister chromatids exist, DSBs result in damage-induced cohesion (DI-cohesion), which is believed to help DSB repair. However, in animal cells, the underlying molecular mechanisms remain unclear. To address it, we conducted IP-MS to screen possible cohesin regulators interacting with Sororin, an essential cohesion establishment factor in metazoan. Interestingly, we identified an uncharacterized 14 kDa microprotein. Time-lapse imaging revealed that this microprotein accumulates at DSB sites within 5 seconds then leaves in 6 minutes. Therefore, we named it Meteor according to this phenomenon. Our preliminary data showed that knockdown of Meteor leads to a decreased HR and an increased NHEJ repair efficiency of DSBs. Based on these results, we propose to address the molecular mechanisms of Meteor in the DI-cohesion and in the DSB repair pathway choice. Besides that, data from the TCGA database indicate that Meteor expresses abnormally in a variety of cancers. Using mammalian cell lines and mice as working models, we will elucidate Meteor’s roles in tumorigenesis and metastasis. The outcome of this study will not only deepen our knowledge of microproteins, the “dark proteome”, in maintaining genome stability, but also help identify novel markers and targets for the diagnosis and therapy of the related cancers.