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标题：Biochemical basis for the essential genetic requirements of RecA and the β-clamp in Pol V activation
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作者：Shingo Fujii ; Robert P. Fuchs
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：35
页码：14825-14830
DOI：10.1073/pnas.0905855106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In Escherichia coli, it is genetically well established that the {beta}-clamp and RecA are essential cofactors that endow DNA polymerase (Pol) V with lesion bypass activity. However, the biochemical basis for these requirements is still largely unknown. Because the process of translesion synthesis (TLS) requires that the specialized DNA polymerase synthesize in a single binding event a TLS patch that is long enough to resist external proofreading, it is critical to monitor Pol V burst synthesis. Here, we dissect the distinct roles that RecA and the {beta}-clamp perform during the Pol V activation process using physiologically relevant long single-stranded template DNA, similar to those used in genetic assays. Our data show that the {beta}-clamp endows the complex between Pol V and the template DNA with increased stability. Also, the RecA filament formed in cis on the single-stranded DNA produced downstream from the lesion stretches the template DNA to allow smooth elongation of the nascent strand by Pol V. The concurrent action of both cofactors is required for achieving productive TLS events. The present article presents an integrated view of TLS under physiologically relevant conditions in E. coli that may represent a paradigm for lesion bypass in other organisms.