Required for normal progression of S-phase. Involved in the circadian rhythm autoregulatory loop. Negatively regulates CLOCK-NPAS2/BMAL1-induced transactivation of PER1 possibly via translocation of PER1 into the nucleus. Promotes TIPIN nuclear localiZation. Involved in cell survival after DNA damage or replication stress. May be specifically required for the ATR-CHK1 pathway in the replication checkpoint induced by hydroxyurea or ultraviolet light. May also play an important role in epithelial cell morphogenesis and formation of branching tubules.