本项目申请内容对应的指南重点资助方向为生物大分子动态修饰的调控机制与功能解析，研究重点为阐明ADP核糖基化修饰对生物大分子凝集和相变过程的调控机制与生物功能。细胞基因组在内外环境诱变剂的作用下不断产生损伤，需依赖DNA损伤应答机制维持基因组稳定性，防止细胞癌变。近期研究发现PolII关闭基因转录以促进DNA修复，但细胞感知DNA损伤并阻滞PolII转录的分子机制尚不清楚。我们的前期工作发现DNA损伤应答激活时，PARP1结合并催化转录因子CycT1发生ADP核糖基化修饰。CycT1以相分离机制促进基因转录延伸，初步结果显示ADP核糖基化修饰对CycT1的相变过程具有调控作用，进而影响转录应答。拟进行的工作将深入探讨CycT1发生ADP核糖基化修饰调控相变的分子机制，揭示其对DNA修复和细胞应激响应的影响，从而加深我们对ADP核糖基化修饰的理解，为发现新药靶点提供科学依据。

Mammalian cells are constantly challenged by genotoxic stresses that cause DNA damage. Organisms have evolved a complex of signaling pathways, termed DNA damage response (DDR), to maintain genome integrity. DNA damage is known to trigger the genome-wide shutdown of transcription to prevent the fatal collisions between elongating RNA polymerase II (Pol II) and DNA repair machinery, but the molecular mechanisms through which cells transmit the DNA damage signal to halt the transcribing Pol II remain mostly unknown. Our preliminary data found that DNA damage-activated PARP1 directly binds and PARylates CycT1, a cyclin partner paired with CDK9 to promote transcription elongation via liquid-liquid phase separation mechanism. We further established the potential link between ADP-ribosylation and phase separation by CycT1. In this proposal, we aim to elucidate the mechanism by which PARP1 modulates CycT1 phase separation and transcription elongation through ADP-ribosylation, unraveling the unprecedented role of this regulation in DNA damage response. The successful outcome of this work will not only deepen our mechanistic understanding of protein ADP-ribosylation but also point the way toward a novel therapy strategy targeting this important PTM for disease treatment.