Functions of Alternative Replication Protein A in Initiation and Elongation

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• 作者：Aaron C. Mason ; Rupa Roy ; Daniel T. Simmons ; Marc S. Wold
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：July 20, 2010
• 年：2010
• 卷：49
• 期：28
• 页码：5919-5928
• 全文大小：1064K
• 年卷期：v.49,no.28(July 20, 2010)
• ISSN：1520-4995

文摘

Replication protein A (RPA) is a single-stranded DNA-binding complex that is essential for DNA replication, repair, and recombination in eukaryotic cells. In addition to this canonical complex, we have recently characterized an alternative replication protein A complex (aRPA) that is unique to primates. aRPA is composed of three subunits: RPA1 and RPA3, also present in canonical RPA, and a primate-specific subunit RPA4, homologous to canonical RPA2. aRPA has biochemical properties similar to those of the canonical RPA complex but does not support DNA replication. We describe studies that aimed to identify what properties of aRPA prevent it from functioning in DNA replication. We show aRPA has weakened interaction with DNA polymerase α (pol α) and that aRPA is not able to efficiently stimulate DNA synthesis by pol α on aRPA-coated DNA. Additionally, we show that aRPA is unable to support de novo priming by pol α. Because pol α activity is essential for both initiation and Okazaki strand synthesis, we conclude that the inability of aRPA to support pol α loading causes aRPA to be defective in DNA replication. We also show that aRPA stimulates synthesis by DNA polymerase α in the presence of PCNA and RFC. This indicates that aRPA can support extension of DNA strands by DNA polymerase ∂. This finding along with the previous observation that aRPA supports early steps of nucleotide excision repair and recombination indicates that aRPA can support DNA repair synthesis that requires polymerase δ, PCNA, and RFC and support a role for aRPA in DNA repair.