Replication protein A (RPA) is the major protein that binds to single-stranded DNA (ssDNA) in eukaryotic cells.[1][2] In vitro, RPA shows a much higher affinity for ssDNA than RNA or double-stranded DNA.[3] RPA is required in replication, recombination and repair processes such as nucleotide excision repair and homologous recombination.[2][4] It also plays roles in responding to damaged DNA.[4]