Genetic control of translesion synthesis on leading and lagging DNA strands in plasmids derived from Epstein-Barr virus in human cells.
Genetic control of translesion synthesis on leading and lagging DNA strands in plasmids derived from Epstein-Barr virus in human cells.
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作者：
Yoon JH;Prakash S;Prakash L
复制DNA聚合酶（Pols）在模板链块合成中的DNA损伤。真核细胞具有许多特殊的翻译合成（TLS） pol，具有通过DNA损伤复制的能力。爱泼斯坦-巴尔病毒（EBV）是疱疹病毒家族的一员，感染人类B细胞并作为染色体外复制子维持在那里，在S期每周期复制一次。除了需要病毒编码的起源结合蛋白EBNA1外，含有EBV复制起源（oriP）的质粒的复制受控制染色体复制的相同细胞过程的控制。由于EBV质粒的复制与人类染色体DNA的复制非常相似，在本研究中，我们研究了双质粒中TLS的遗传控制，其中双向复制始于EBV oriP原点，紫外线诱导的顺式同步TT二聚体位于前导链或滞后链DNA模板上。在这里，我们发现TLS在EBV质粒的两条DNA链上发生的频率相同，并且无论哪条DNA链携带病变，TLS pol的要求都是相同的。我们讨论了这些观察结果对染色体复制过程中作用于两条DNA链的TLS机制的影响，并得出结论，在人类细胞中前导和滞后DNA链的复制过程中，相同的遗传机制支配着TLS。由于EBV （Epstein-Barr病毒）起源质粒的复制利用了细胞机制来完成复制的所有步骤，我们观察到EBV质粒的两条DNA链上的翻译合成（TLS）的遗传机制相同，这意味着tlspol的需求不受复制pol或其他可能用于人类细胞中两条DNA链复制的蛋白质的任何差异的影响。这些发现对于评估我们之前报道的基于SV40起源的质粒的TLS研究结果的意义也具有重要意义，我们在其中表明TLS在两条DNA链上相似地发生。由于SV40质粒中TLS的遗传控制与EBV质粒相似，我们得出结论，SV40质粒的TLS研究与EBV质粒的TLS研究一样，可以提供细胞复制过程中TLS机制的信息。
DNA lesions in the template strand block synthesis by replicative DNA polymerases (Pols). Eukaryotic cells possess a number of specialized translesion synthesis (TLS) Pols with the ability to replicate through DNA lesions. The Epstein-Barr virus (EBV), a member of the herpesvirus family, infects human B cells and is maintained there as an extrachromosomal replicon, replicating once per cycle during S phase. Except for the requirement of the virus-encoded origin-binding protein EBNA1, replication of plasmids containing the EBV origin of replication (oriP) is controlled by the same cellular processes that govern chromosomal replication. Since replication of EBV plasmid closely mimics that of human chromosomal DNA, in this study we examined the genetic control of TLS in a duplex plasmid in which bidirectional replication initiates from an EBV oriP origin and a UV-induced cis-syn TT dimer is placed on the leading- or the lagging-strand DNA template. Here we show that TLS occurs equally frequently on both the DNA strands of EBV plasmid and that the requirements of TLS Pols are the same regardless of which DNA strand carries the lesion. We discuss the implications of these observations for TLS mechanisms that operate on the two DNA strands during chromosomal replication and conclude that the same genetic mechanisms govern TLS during the replication of the leading and the lagging DNA strands in human cells. Since replication of EBV (Epstein-Barr virus) origin-based plasmids appropriates the cellular machinery for all the steps of replication, our observations that the same genetic mechanisms govern translesion synthesis (TLS) on the two DNA strands of EBV plasmids imply that the requirements of TLS Pols are not affected by any of the differences in the replicative Pols or in other proteins that may be used for the replication of the two DNA strands in human cells. These findings also have important implications for evaluating the significance of results of TLS studies with the SV40 origin-based plasmids that we have reported previously, in which we showed that TLS occurs similarly on the two DNA strands. Since the genetic control of TLS in SV40 plasmids resembles that in EBV plasmids, we conclude that TLS studies with the SV40 plasmids are as informative of TLS mechanisms that operate during cellular replication as those with the EBV plasmids.