Miyoshi Tomoichiro, Makino Takeshi, Moran John V
Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Stress Response, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109-5618, USA.
Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Stress Response, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
Mol Cell. 2019 Sep 19;75(6):1286-1298.e12. doi: 10.1016/j.molcel.2019.07.018. Epub 2019 Aug 28.
Long interspersed element-1 (LINE-1 or L1) retrotransposition poses a threat to genome integrity, and cells have evolved mechanisms to restrict retrotransposition. However, how cellular proteins facilitate L1 retrotransposition requires elucidation. Here, we demonstrate that single-strand DNA breaks induced by the L1 endonuclease trigger the recruitment of poly(ADP-ribose) polymerase 2 (PARP2) to L1 integration sites and that PARP2 activation leads to the subsequent recruitment of the replication protein A (RPA) complex to facilitate retrotransposition. We further demonstrate that RPA directly binds activated PARP2 through poly(ADP-ribosyl)ation and can protect single-strand L1 integration intermediates from APOBEC3-mediated cytidine deamination in vitro. Paradoxically, we provide evidence that RPA can guide APOBEC3A, and perhaps other APOBEC3 proteins, to sites of L1 integration. Thus, the interplay of L1-encoded and evolutionarily conserved cellular proteins is required for efficient retrotransposition; however, these interactions also may be exploited to restrict L1 retrotransposition in the human genome.
长散在核元件1（LINE-1或L1）逆转录转座对基因组完整性构成威胁，细胞已进化出限制逆转录转座的机制。然而，细胞蛋白如何促进L1逆转录转座尚需阐明。在此，我们证明L1核酸内切酶诱导的单链DNA断裂会触发聚（ADP-核糖）聚合酶2（PARP2）募集至L1整合位点，且PARP2激活会导致随后复制蛋白A（RPA）复合物的募集，以促进逆转录转座。我们进一步证明，RPA通过聚（ADP-核糖基）化直接结合活化的PARP2，并且在体外可保护单链L1整合中间体免受载脂蛋白B mRNA编辑酶催化多肽样3（APOBEC3）介导的胞嘧啶脱氨作用。矛盾的是，我们提供的证据表明，RPA可将APOBEC3A以及可能的其他APOBEC3蛋白引导至L1整合位点。因此，高效逆转录转座需要L1编码的细胞蛋白与进化上保守的细胞蛋白之间的相互作用；然而，这些相互作用也可能被用于限制人类基因组中的L1逆转录转座。
