DNA helicase that may play a role in the repair of DNA that is damaged by ultraviolet light or other mutagens. Exhibits a magnesium-dependent ATP-dependent DNA-helicase activity that unwinds single- and double-stranded DNA in a 3'-5' direction. ATP + H2O = ADP + H(+) + phosphate dATP + H2O = dADP + H(+) + phosphate Interacts with EXO1 (PubMed:15886194). Interacts with MLH1. High expression in heart, lung, skeletal muscle and kidney, low expression in brain. Belongs to the helicase family. RecQ subfamily.