BoHV-1感染抑制53BP1依赖的对DNA损伤进行修复的分子机理研究

牛呼吸道综合征（BRDC）对养牛业危害巨大，BoHV-1感染牛对呼吸道黏膜造成损伤是引起BRDC发生的重要诱因；该病毒复制致呼吸道黏膜损伤的分子机制并不清楚。病毒感染牛肾细胞和牛胚气管细胞均诱导DNA损伤；已知53BP1/RIF1信号主导对损伤DNA中断裂双链的修复。初步研究首次发现，HMGA1与53BP1及其下游效应分子RIF1结合形成复合物、该病毒感染影响该复合物中多个组分的表达水平、53BP1核转运及53BP1与RIF1的结合；在此提出假设：病毒感染经HMGA1和/或特定病毒蛋白扰乱53BP1/RIF1信号网络中多组分的功能而抑制该信号对损伤DNA的修复，另外DNA损伤是病毒复制致黏膜损伤的重要因素。如果假设被证实，将首次揭示HMGA1分子调节DNA损伤这一新的生物学功能，并深入揭示该病毒诱导DNA损伤产生的分子机理；对于该病毒的致病机制和DNA损伤修复机制的理论研究均具有重要意义。

Due to the mucosal lesion and immune depression developed during bovine herpesvirus 1 (BoHV-1) acute infection, a secondary infection by diverse bacteria or viruses tends to occur, which consequently causes bovine respiratory disease complex (BRDC), the costliest disease for cattle industry. Thus, airway mucosal lesion caused by the virus replication is a primary reason for BRDC development. DNA double-strand breaks (DSBs) pose serious threat to the genome integrity and cell viability. We have recently revealed that BoHV-1 replication in multiple cells, such as MDBK cells (a bovine kidney cell line) and EBTr cells (a bovine trachea cell line) unanimously leads to DNA damage identified by comet assay. We therefore proposed that DNA damage induced by virus replication is potentially associated with the mucosal lesion. 53BP1 (P53-binding protein 1)-dependent end-joining pathway plays a critical role in double strand break repair. 53BP1 is functionally dependent on the association with the downstream effector RIF1 (RAP1-interacting factor 1) which are recruited to the sites around DSBs in response to DDR (DNA damage response) signaling. Recently, our preliminary research for the first time indicated that the molecule HMGA1 (high mobility group AT-hook 1 protein) is associated with both 53BP1 and RIF1 and potentially form an HMGA1/53BP1/RIF1complex. BoHV-1 infection at late stage increased the protein levels of both 53BP1 and HMGA1 but decreased RIF1 expression. In addition, the virus infection inhibited 53BP1 nuclues localization and foci formation, and disrupted the association between 53BP1 and RIF1, which all suggested a potential dysfunction of 53BP1-dependent DNA damage repair. Based on these preliminary data and pertinent publications, we raised a proposal that HMGA1 together with certain virus-encoded proteins interrupted the 53BP1/RIF1 signaling pathways by diverse approaches, which consequently inhibited 53BP1-mediated DNA damage repair. If the involvement of HMGA1 in 53BP1-dependnet DNA damage repair is confirmed in the following study, a novel function of this molecule would be revealed. In addition, we would dissect the viral proteins which are associated with the HGMA1/53BP1/RIF1 complex and corresponding effects on DNA damage repair, and thereby mechanistically characterize how the virus infection induce DNA damage, which would benefit of understanding of how BRDC occurred attributed to the virus infection. In summary, if this application get approved, the following study would not only contribute to understanding of the virus pathogenesis but also be implicated in the field of DNA damage repair in molecular biology.