As part of the alternative replication protein A complex, aRPA, binds single-stranded DNA and probably plays a role in DNA repair. Compared to the RPA2-containing, canonical RPA complex, may not support chromosomal DNA replication and cell cycle progression through S-phase. The aRPA may not promote efficient priming by DNA polymerase alpha but could support DNA polymerase delta synthesis in the presence of PCNA and replication factor C (RFC), the dual incision/excision reaction of nucleotide excision repair and RAD51-dependent strand exchange. Component of the aRPA, the alternative replication protein A complex, a trimeric complex similar to the replication protein A complex/RPA but where RPA1 and RPA3 are associated with RPA4 instead of RPA2. Interacts with RPA1 and RPA3. Localizes to DNA repair foci after DNA damage. Preferentially expressed in placental and colon mucosa. Widely expressed at intermediate or lower levels. Belongs to the replication factor A protein 2 family.