RPA has been referred to by multiple names in the literature including replication protein A, replication factor A (RFA), and human or HeLa single stranded DNA-binding protein (HSSB). It is a protein of heterotrimer composed of three tightly associated subunits of ~70, 32, and 14 kDa (referred as to RPA70, RPA32, and RPA14, respectively) that binds nonspecifically to ssDNA and interacts with and/or modifies the activities of multiple proteins. It is required for multiple processes in eukaryotic DNA metabolism, including DNA replication, DNA repair, and recombination. RPA is found to be potentially involved in cell cycle checkpoints and DNA damage checkpoints, and may have a role in modulating gene expression[1]. In cells, RPA is phosphorylated by DNA-dependent protein kinase when RPA is bound to single-stranded DNA (during S phase and after DNA damage)[2].