Single-stranded 3'-5' DNA helicase that plays a key role in homology-driven double-strand break (DSB) repair (   ). Involved in different DSB repair mechanisms that are guided by annealing of extensive stretches of complementary bases at break ends, such as microhomology-mediated end-joining (MMEJ), single-strand annealing (SSA) or synthesis-dependent strand annealing (SDSA) . Possesses both DNA unwinding and annealing activities . Forms a complex with RAD51, stimulating HELQ DNA helicase activity and ability to unwing DNA . Efficiently unwinds substrates containing 3' overhangs or a D-loop (, ). In contrast, interaction with the replication protein A (RPA/RP-A) complex inhibits DNA unwinding by HELQ but strongly stimulates DNA strand annealing . Triggers displacement of RPA from single-stranded DNA to facilitate annealing of complementary sequences (, ).
Subcellular locations: Nucleus, Chromosome
Localizes to sites of DNA damage; localizes to damaged replication forks.