Anti-RPA2 monoclonal antibody, clone 10I9

Replication protein A (RPA) is a mammalian single-stranded DNA binding factor essential for DNA replication, repair, and recombination. It is composed of three subunits of 70, 34, and 13 kDa (Rpa1, Rpa2, and Rpa3, respectively), Deletion mapping of the Rpa2 subunit identified the domain required for interaction with Rpa1 and Rpa3 which does not include the N-terminal domain that is phosphorylated during S phase, Deletion mapping of Rpa1 defined three domains. The C-terminal third of the Rpa1 polypeptide binds Rpa2 which itself forms a bridge between Rpa1 and Rpa3, The N-terminal third of Rpa1 bound single-stranded DNA under low stringency conditions only (0.1 M NaCl), while a central domain binds to single-stranded DNA under both low and high stringency conditions (0.5 M NaCl), Binding to p53 requires the N-terminal third of Rpa1 with some contribution from the C-terminal third. The evolutionarily conserved putative zinc finger near the C terminus of Rpa1 was not required for binding to single-stranded DNA, Rpa2, or p53, However, all three subdomains of Rpa1 and the zinc finger were essential for supporting DNA replication in vitro. These experiments are a first step toward defining peptide components responsible for the many functions of the RPA protein complex.

Recent results suggest that potentially lethal DNA lesions may result when replication forks encounter trapped topoisomerase-DNA complexes or some other types of DNA damage. Such events produce what are called replication-encounter lesions. These lesions have the characteristic that they may allow single stranded DNA-associated replication protein A (RPA) to become juxtaposed to dsDNA end-associated DNA-protein kinase. Our results suggest that DNA-protein kinases may then hyperphosphorylate the RPA2 subunit. We discuss a possible pathway by which hyperphosphorylation of RPA2 could lead to the release of active p53. This could constitute a pathway for signaling the presence of replication-encounter lesions to the p53-dependent cell cycle arrest and/or apoptosis initiator systems.