Required for G1/S transition. Plays a role in DNA replication checkpoint signaling through regulating rad3 and cds1. Involved in the maintenance of mitotic chromosome structures during S phase through regulating the function of rad21. Required for initiation of mitotic DNA replication through phosphorylating mcm2/cdc19. Required for genome integrity. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Phosphorylation of exogenous substrates activated by Dfp1. Heterodimer with the regulatory subunit him1/dfp1. May form homooligomeric complexes. Interacts with mcm10. Nuclear throughout the cell cycle. Autophosphorylated. Phosphorylated by cds1 in vitro. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CDC7 subfamily.