Department of Biochemistry, Ludwig-Maximilians-University, 81377 Munich, Germany; Gene Center, Ludwig-Maximilians-University, 81377 Munich, Germany.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Mol Cell. 2023 Jan 5;83(1):43-56.e10. doi: 10.1016/j.molcel.2022.12.005.
Endogenous and exogenous agents generate DNA-protein crosslinks (DPCs), whose replication-dependent degradation by the SPRTN protease suppresses aging and liver cancer. SPRTN is activated after the replicative CMG helicase bypasses a DPC and polymerase extends the nascent strand to the adduct. Here, we identify a role for the 5'-to-3' helicase FANCJ in DPC repair. In addition to supporting CMG bypass, FANCJ is essential for SPRTN activation. FANCJ binds ssDNA downstream of the DPC and uses its ATPase activity to unfold the protein adduct, which exposes the underlying DNA and enables cleavage of the adduct. FANCJ-dependent DPC unfolding is also essential for translesion DNA synthesis past DPCs that cannot be degraded. In summary, our results show that helicase-mediated protein unfolding enables multiple events in DPC repair.
内源性和外源性因子会产生 DNA-蛋白质交联（DPCs），这些交联物的复制依赖性降解由 SPRTN 蛋白酶来抑制衰老和肝癌。当复制性 CMG 解旋酶绕过 DPC 时，SPRTN 被激活，然后聚合酶将新生链延伸到加合物上。在这里，我们发现 FANCJ 解旋酶在 DPC 修复中起着作用。除了支持 CMG 绕过之外，FANCJ 对于 SPRTN 的激活也是必不可少的。FANCJ 结合在 DPC 下游的单链 DNA 上，并利用其 ATP 酶活性展开蛋白质加合物，从而暴露潜在的 DNA，并能够切割加合物。FANCJ 依赖性 DPC 展开对于不能降解的 DPC 处的跨损伤 DNA 合成也是必不可少的。总之，我们的研究结果表明，解旋酶介导的蛋白质展开使 DPC 修复中的多个事件成为可能。
