Serine/threonine-protein kinase which is required for checkpoint-mediated cell cycle arrest and activation of DNA repair in response to the presence of DNA damage or unreplicated DNA. May also negatively regulate cell cycle progression during unperturbed cell cycles. Controls phosphorylation and abundance of PDS1 to prevent anaphase entry. Also helps prevent mitotic exit. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Present with 2530 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. NIM1 subfamily.