Replication-dependent and -independent responses of RAD18 to DNA damage in human cells
Replication-dependent and -independent responses of RAD18 to DNA damage in human cells
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DOI：
10.1074/jbc.m605545200
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发表时间：
2006-11-10
影响因子：
4.8
通讯作者：
Yasui, Akira
中科院分区：
文献类型：
--
作者：
Nakajima, Satoshi;Lan, Li;Yasui, Akira
复制后修复促进了复制过程中DNA损伤的耐受性，克服了DNA损伤位点的复制终止。哺乳动物细胞复制后修复的一个主要途径是翻译合成，这是由特殊的聚合酶（如聚合酶eta）进行的，并通过UVC光照射后聚合酶形成的焦点来识别。这些病灶的形成依赖于RAD18，它使PCNA泛素化以交换聚合酶。为了了解翻译合成的初始过程，我们在这里分析了RAD18在人类细胞中对损伤的反应。我们发现，人类RAD18以细胞周期无关的方式，在不同类型的DNA损伤位点（包括UVC光诱导的损伤、x射线微束和激光诱导的单链断裂）积累得非常快，并持续很长一段时间。即使DNA复制受到抑制，也可以观察到RAD18在DNA损伤处的积累，并且位于RAD18中间的一个含有锌指基序的小区域对于不依赖复制的损伤积累是必要和充分的。uv诱导的聚合酶eta焦点形成不需要RAD18的锌指基序，但锌指附近需要另一个SAP基序（SAF-A/B、Acinus和PIAS）。这些数据表明RAD18以两种不同的方式响应DNA损伤，一种依赖复制，另一种不依赖复制，分别涉及SAP和锌指基序。
Postreplication repair facilitates tolerance of DNA damage during replication, overcoming termination of replication at sites of DNA damage. A major post-replication repair pathway in mammalian cells is translesion synthesis, which is carried out by specialized polymerase(s), such as polymerase eta, and is identified by focus formation by the polymerase after irradiation with UVC light. The formation of these foci depends on RAD18, which ubiquitinates PCNA for the exchange of polymerases. To understand the initial processes in translesion synthesis, we have here analyzed the response to damage of RAD18 in human cells. We find that human RAD18 accumulates very rapidly and remains for a long period of time at sites of different types of DNA damage, including UVC light-induced lesions, and x-ray microbeam- and laser-induced single-strand breaks, in a cell cycle-independent manner. The accumulation of RAD18 at DNA damage is observed even when DNA replication is inhibited, and a small region containing a zinc finger motif located in the middle of RAD18 is essential and sufficient for the replication-independent damage accumulation. The zinc finger motif of RAD18 is not necessary for UV-induced polymerase eta focus formation, but another SAP (SAF-A/B, Acinus and PIAS) motif near the zinc finger is required. These data indicate that RAD18 responds to DNA damage in two distinct ways, one replication-dependent and one replication-independent, involving the SAP and zinc finger motifs, respectively.