The Role of Mono-ADP-Ribosylation by PARP14 in Radioresistance

 描述（由申请人提供）：电离辐射通过产生DNA损伤杀死癌细胞。对电离辐射的抵抗力通常由DNA修复机制决定，该机制可以修复辐射诱导的DNA损伤。辐射的最大毒性作用表现为形成双链DNA断裂。这些断裂可以通过同源末端连接和非同源末端连接DNA修复机制来修复。这些机制的抑制导致辐射敏感性增加，因为辐射诱导的双链断裂的修复被阻断。因此，了解双链断裂修复的分子机制对于设计新的放射增敏疗法至关重要。 我们最近发现了一种调节辐射抗性的新机制，以蛋白质PARP 14为中心。PARP 14是一种单ADP核糖基转移酶，与其众所周知的表亲PARP 1不同，PARP 14不能催化聚ADP核糖链的形成，但只能将单个ADP核糖分子转移到底物上。单ADP核糖基化是一种神秘的翻译后修饰，其在细胞中的功能还不清楚。或者，本文提供的初步结果表明，PARP 14通过激活同源重组DNA修复来促进双链断裂的修复。此外，我们的初步结果表明，这种激活的机制：PARP 14单ADP核糖基化的重组因子RAD 51，以促进RAD 51从D-环，从而允许D-环延伸过去的断裂和完成重组反应。因此，我们的工作表明，PARP 14抑制通过下调辐射诱导的双链DNA断裂的Homoprotein依赖性修复而导致辐射敏感性。 在这个建议中，我们测试的假设，PARP 14促进修复辐射诱导的双链DNA断裂的Homoproteination，通过RAD 51单ADP核糖基化。我们将采用全面、综合的方法来研究：1）PARP 14对通过同源重组和其他DNA修复机制修复辐射诱导的DNA损伤的影响，以及2）PARP 14对RAD 51单ADP核糖基化在修复辐射诱导的双链断裂中的作用。 我们的研究是高度创新的，因为它解决了一个新的，以前未被认识到的功能的单ADP核糖基化的辐射抗性。我们的工作将揭示PARP 14的单ADP核糖基化如何促进辐射抗性，并描述基于PARP 14抑制的新型放射增敏方法。

 DESCRIPTION (provided by applicant): Ionizing Radiation kills cancer cells by generating DNA damage. Resistance to Ionizing Radiation is generally determined by DNA repair mechanisms that can repair radiation-induced DNA damage. The most toxic effect of radiation is represented by the formation of double stranded DNA breaks. These breaks can be repaired by Homologous Recombination, and Non-Homologous End Joining DNA repair mechanisms. Inhibition of these mechanisms results in increased radiosensitivity since repair of radiation-induced double strand breaks is blocked. Thus, understanding the molecular mechanisms of double strand break repair is essential for designing novel radiosensitization therapies. We have recently uncovered a novel mechanism that regulates radioresistance, centered on the protein PARP14. PARP14 is a mono-ADP-ribosyltransferase, which unlike its well-known cousin PARP1 is unable to catalyze poly-ADP-ribose chain formation but can only transfer a single molecule of ADP-ribose to substrates. Mono-ADP-ribosylation is a still mysterious post-translational modification, and its functions in the cell are poorly characterized. Or preliminary results presented here show that PARP14 promotes repair of double strand breaks by activating Homologous Recombination DNA repair. Moreover, our preliminary results presented here indicate a mechanism for this activation: PARP14 mono-ADP-ribosylates the recombination factor RAD51 to promote RAD51 removal from D-loops thus allowing D-loop extension past the break and complete the recombination reaction. Thus, our work shows that PARP14 inhibition results in radiosensitivity by downregulating Homologous Recombination-dependent repair of radiation-induced double strand DNA breaks. In this proposal, we test the hypothesis that PARP14 promotes the repair of radiation-induced double strand DNA breaks by Homologous Recombination, through RAD51 mono-ADP-ribosylation. We will employ a comprehensive, integrative approach to study: 1) the impact of PARP14 on the repair of radiation-induced DNA damage by Homologous Recombination and other DNA repair mechanisms, and 2) the role of RAD51 mono- ADP-ribosylation by PARP14 in repair of radiation-induced double strand breaks. Our study is highly innovative since it addresses a novel, previously unrecognized function of mono- ADP-ribosylation in radioresistance. Our work will unravel how mono-ADP-ribosylation by PARP14 promotes radiation resistance, and describe novel radiosensitization approaches, based on PARP14 inhibition.