Key enzyme involved in DNA replication and DNA repair. Involved in Okazaki fragments processing by cleaving long flaps that escape FEN1: flaps that are longer than 27 nucleotides are coated by replication protein A complex (RPA), leading to recruit DNA2 which cleaves the flap until it is too short to bind RPA and becomes a substrate for FEN1. Also involved in 5'-end resection of DNA during double-strand break (DSB) repair by mediating the cleavage of 5'-ssDNA. Possesses different enzymatic activities, such as single-stranded DNA (ssDNA)-dependent ATPase, 5'-3' helicase and endonuclease activities. While the ATPase and endonuclease activities are well-defined and play a key role in Okazaki fragments processing and DSB repair, the 5'-3' DNA helicase activity is atypical: it cannot load onto its tracking strand internally and has an absolute free 5'-end requirement. Helicase activity may promote the motion of DNA2 on the flap, helping the nuclease function. ATP + H2O = ADP + H(+) + phosphate Binds 1 [4Fe-4S] cluster. Recruited to double-strand. break (DSB) sites following phosphorylation at Ser-17 and Ser-237. Phosphorylated at Ser-17 and Ser-237 by CDK1 in response to DNA damage, leading to promote recruitment to double-strand break (DSB) sites and DNA resection. Belongs to the DNA2/NAM7 helicase family.