HTLV-1 Tax Disrupts DNA Damage Repair-Response Complexes

描述（申请人提供）：人类t细胞白血病病毒1型（HTLV-1）引起成人t细胞白血病（ATL）。虽然确切的机制尚不清楚，但细胞转化依赖于病毒蛋白Tax的表达。我们和其他人已经证明，Tax的表达导致基因组不稳定，我们假设基因组完整性的丧失促进了htlv -1介导的白血病发生。本应用程序的目的是揭示通过税收破坏正常细胞DNA损伤反应（DDR），从而导致基因组完整性损失的机制。我们假设Tax形成一种损伤独立的DDR复合物，竞争性地抑制正常细胞的DDR。受损的DDR有助于基因组的不稳定性，因此我们提出了ATL的发展模型。我们的假设是基于我们发表的研究结果和初步数据，即Tax可以将DDR蛋白招募到不与DNA损伤位点共定位的核病灶。我们发现，Tax与MDC1结合，并将这种DDR蛋白招募到损伤无关的病灶，我们之前将其确定为Tax斑点结构（TSS）。由于最近有研究表明，MDC1与DNA的人工拴系足以启动DDR，我们提出，通过招募MDC1等蛋白质，Tax启动了损伤无关的DDR。我们的假设将在三个具体目标中得到检验。1)鉴定驱动TSS和DNA损伤诱导的核病灶之间竞争的DDR蛋白2)TSS的结构表征和驱动TSS形成的税收特征3)确定竞争对DDR复合物招募到TSS的功能意义。这些研究的成功完成将有助于确定一种新的病毒-细胞相互作用策略，并为更好地理解DDR和细胞转化提供帮助。

DESCRIPTION (provided by applicant): Human T-cell Leukemia Virus type 1 (HTLV-1) causes Adult T-cell Leukemia (ATL). Although the precise mechanism is unknown, cellular transformation is dependent upon expression of the viral protein Tax. We and others have shown that expression of Tax results in genomic instability and we hypothesize that loss of genomic integrity facilitates HTLV-1-mediated leukemogenesis. The objective of this application is to uncover the mechanism by which Tax disrupts normal cellular DNA damage response (DDR) and thus results in loss of genomic integrity. We hypothesize that Tax forms a damage- independent DDR complex that competitively inhibits normal cellular DDR. The impaired DDR contributes to genomic instability and thus we present a model for development of ATL. Our hypothesis is based upon our published findings and preliminary data establishing that Tax can recruit DDR proteins to nuclear foci that do not colocalize with sites of DNA damage. We show that Tax binds to MDC1 and recruits this DDR protein to damage-independent foci that we have previously identified as Tax Speckled Structures (TSS). Since it has been recently shown that artificial tethering of MDC1 to DNA is sufficient to initiate DDR, we propose that Tax initiates damage-independent DDR by recruiting proteins like MDC1. Our hypothesis will be tested in three specific aims. 1) Identification of DDR Proteins that Drive Competition between TSS and DNA Damage Induced Nuclear Foci. 2) Structural Characterization of TSS and Features of Tax that Drive TSS Formation. 3) Determine the Functional Significance of Competition for Recruitment of DDR Complexes to TSS. Successful completion of these studies will help define a novel virus-cell interaction strategy and provide for a better understanding of DDR and cellular transformation.