5'-3' DNA helicase involved in DNA damage response by acting as an inhibitor of DNA end resection (PubMed:26774285). Recruitment to single-stranded DNA (ssDNA) following DNA damage leads to inhibit the nucleases catalyzing resection, such as EXO1, BLM and DNA2, possibly via the 5'-3' ssDNA translocase activity of HELB (PubMed:26774285). As cells approach S phase, DNA end resection is promoted by the nuclear export of HELB following phosphorylation (PubMed:26774285). Acts independently of TP53BP1 (PubMed:26774285). Unwinds duplex DNA with 5'-3' polarity. Has single-strand DNA-dependent ATPase and DNA helicase activities. Prefers ATP and dATP as substrates. During S phase, may facilitate cellular recovery from replication stress (PubMed:11557815, PubMed:7596831, PubMed:7794903). ATP + H2O = ADP + H(+) + phosphate Binds to RPA1; this interaction promotes HELB recruitment to chromatin following DNA damage. Interacts with at least two subunits of the DNA polymerase alpha complex. Interacts with CDC45. Interacts with TOPB1. Predominantly nuclear. Phosphorylation at Ser-942 by CDK2 during the G1/S transition results in its nuclear export into the cytoplasm as cells approach and progress through S phase. Following DNA damage, recruited to sites of double-strand breaks by the RPA complex. Phosphorylated at Ser-942 by CDK2 during the G1/S transition, resulting in its nuclear export into the cytoplasm. As S phase progresses, its exclusion from the nucleus promotes the activation of long-range resection. Belongs to the RecD family. HELB subfamily.