Replication Protein A (RPA): The Eukaryotic SSB

Replication protein A (RPA) is a heterotrimeric single-stranded DNA-binding protein that is highly conserved in eukaryotes. RPA plays essential roles in many aspects of nucleic acid metabolism, including DNA replication, nucleotide excision repair, and homologous recombination. In this review, we provide a comprehensive overview of RPA structure and function and highlight the more recent developments in these areas. The last few years have seen major advances in our understanding of the mechanism of RPA binding to DNA, including the structural characterization of the primary DNA-binding domains (DBD) and the identification of two secondary DBDs. Moreover, evidence indicates that RPA utilizes a multistep pathway to bind single-stranded DNA involving a particular molecular polarity of RPA, a mechanism that is apparently used to facilitate origin denaturation. In addition to its mechanistic roles, RPA interacts with many key factors in nucleic acid metabolism, and we discuss the critical nature of many of these interactions to DNA metabolism. RPA is a phosphorylation target for DNA-dependent protein kinase (DNA-PK) and likely the ataxia telangiectasia-mutated gene (ATM) protein kinase, and recent observations are described that suggest that RPA phosphorylation plays a significant modulatory role in the cellular response to DNA damage.