Has a role in the repair of UV-induced DNA damage in G2 via recombination-mediated repair. Also has a role in the repair of infrared-induced double DNA strand breaks. Exhibits an ATP-dependent DNA-helicase activity that unwinds single- and double-stranded DNA in a 3'-5' direction. ATP + H2O = ADP + H(+) + phosphate Interacts with top3. Belongs to the helicase family. RecQ subfamily.