Plays an important role in the control of DNA replication and the maintenance of replication fork stability. Important for cell survival after DNA damage or replication stress. May be specifically required for the ATR-CHEK1 pathway in the replication checkpoint induced by hydroxyurea or ultraviolet light. Forms a complex with TIMELESS and this complex regulates DNA replication processes under both normal and stress conditions, stabilizes replication forks and influences both CHEK1 phosphorylation and the intra-S phase checkpoint in response to genotoxic stress. Interacts with MCM6 and MCM7 (By similarity). Interacts with TIMELESS, which impairs TIMELESS self-association. Interacts with RPA2 and PRDX2. Expressed in brain. Expression peaks between 11 dpc and 15 dpc. At 7.5 dpc, expressed in germ cell layers. At 14.5 dpc, expressed at highest levels in thymus, liver, gastrointestinal tract, lung and the rapidly proliferating ventricular zone of the brain. Belongs to the CSM3 family.