The RPA2 gene is contained within 24.5 kb of chromosome 1. The coding sequence is contained within nine exons. There is no confirmed alternative splicing of the RPA2 gene, or differential promoter usage.

The RPA2 mRNA transcript is 1.5 kb. The RPA2 promoter contains four E2F consensus sequences within the region about 400 bp upstream of the mRNA start site, and putative binding sites for ATF-1 and SP-1 transcription factors. Expression is upregulated 2 to 3-fold by E2F, with mutation of the three start site-proximal E2F sites causing a loss of E2F responsiveness (Kalma et al., 2001).

RPA2 does not have known pseudogenes.

RPA2 is the middle subunit of the heterotrimeric Replication Protein A (RPA; (reviewed in Binz et al., 2004)). The subunit is composed of 270 residues, and has a nominal molecular weight of 29.2 kDa. RPA2 contains an N-terminal phosphorylation region with 7 phosphorylation sites, a central DNA-binding domain (termed DBD-D), and a C-terminal region that can form a three-helix bundle. One helix of the three helix bundle is contributed by each RPA subunit, with this structure responsible for supporting heterotrimerization of the RPA complex (Bochkareva et al., 2002). At least in the non-phosphorylated state, the N-terminal region is unstructured. DBD-D is constructed from an oligonucleotide/oligosaccharide binding (OB) fold (Bochkarev et al., 1999), one of six OB folds found with the RPA heterotrimer (four OB folds are located in RPA1, and one within RPA3).

RPA is an essential factor for DNA replication and repair, and hence is expressed in all tissues.

Nuclear.

General function: RPA is a heterotrimeric single-stranded DNA (ssDNA) binding protein that is essential for chromosomal DNA replication, homologous recombination, and particular DNA repair reactions (nucleotide excision repair). The apparent association constant of the RPA: ssDNA complex is 10⁹ - 10¹¹ M^-1 (Kim et al., 1992). While RPA2 contains a central DBD (Philipova et al., 1996), the major effect of mutating DBD-D is to decrease the size of the ssDNA occluded by RPA binding, with only minor effects on RPA: ssDNA affinity (Bastin-Shanower and Brill, 2001). A key function of the RPA2 subunit is to regulate RPA activity in DNA replication and repair reactions, through the RPA2 phosphorylation state (see below).

1) RPA2 phosphorylation. The N-terminal 33 residues of RPA2 contain seven phosphorylation sites. In interphase cells, genotoxic stress (e.g., caused by chromosomal double-strand DNA breaks or DNA replication stress) induces RPA2 phosphorylation by members of the phosphatidylinositol 3-kinase-like kinase (PIKK; ATM, ATR, and DNA-PK) and cyclin-dependent kinases (CDK) families (reviewed in Binz et al., 2004). Mutation of particular RPA2 phosphorylation sites causes defects in homologous recombination (Lee et al., 2010), and Rad51 recruitment to nuclear repair foci (Anantha et al., 2008; Lee et al., 2010). Mutation of these sites also causes genomic instability in response to DNA replication stress induced by cellular treatment with hydroxyurea (Vassin et al., 2009). RPA phosphorylation also increases cell viability in response to DNA damage arising during mitosis (Anantha et al., 2008). Modification of sites in the phosphorylation region of RPA2 proceeds in a favored order in response to genotoxic stress (Anantha et al., 2007). The phosphorylation of individual RPA2 residues is dependent on the type of DNA damage or replication stress encountered (Anantha et al., 2007; Vassin et al., 2009). RPA2 is a substrate both for PP2A and PP4 phosphatases (Feng et al., 2009; Lee et al., 2010).

2) Involvement of RPA2 in protein-protein interactions. RPA2 interacts with the nucleotide excision repair factor XPA (He et al., 1995), base excision repair enzyme UNG2 (Mer et al., 2000), homologous recombination (HR) factor Rad52 (Mer et al., 2000), replication checkpoint protein Tipin (Unsal-Kacmaz et al., 2007), and the annealing helicase HARP/SMARCAL1 (Bansbach et al., 2009; Ciccia et al., 2009; Yuan et al., 2009). These interactions likely aid the multiple roles of RPA in facilitating DNA repair.

A close homolog of RPA2, termed RPA4, is located on Xq21.33 (Haring et al., 2010).

Naturally-occurring mutations of human RPA2 have not yet been described. A small number of genetic polymorphisms have been described in SNP datasets (Y14S, G15R, and N203S), but these have not yet been reported to have any biological effects (NIEHS SNPs program).