Distinct functions of human RECQ helicases WRN and BLM in replication fork recovery and progression after hydroxyurea-induced stalling

► WRN and BLM human RECQ helicases contribute additively to fork progression during normal replication. ► After short-term HU block, fork restart requires non-additive contributions of BLM, WRN, and RAD51 that do not involve protection from DSBs. ► BLM but not WRN is required for timely G2/M transition after short-term HU block. ► Human fibroblasts appear to replace or degrade some of the DNA synthesized by recovering forks during the first hour after release from HU.