Structure of the single-stranded-DNA-binding domain of replication protein A bound to DNA

Abstract

THE single-stranded-DNA-binding proteins (SSBs) are essential for DNA function in prokaryotic and eukaryotic cells, mitochondria, phages and viruses^1,2. The structures of four SSBs have been solved^3–7, but the molecular details of the interaction of SSBs with DNA remain speculative. We report here the crystal structure at 2.4 Å resolution of the single-stranded-DNA-binding domain of human replication protein A (RPA) bound to DNA. Replication protein A is a heterotrimeric SSB that is highly conserved in eukaryotes. The largest subunit, RPA70, binds to single-stranded (ss)DNA^8,9 and mediates interactions with many cellular and viral proteins¹⁰. The DNA-binding domain, which lies in the middle of RPA70, comprises two structurally homologous sub-domains oriented in tandem. The ssDNA lies in a channel that extends from one subdomain to the other. The structure of each RPA70 subdomain is similar to those of the bacteriophage SSBs, indicating that the mechanism of ssDNA-binding is conserved.