Probable serine/threonine-protein kinase that may be involved in ribosome biogenesis. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with ribosome biogenesis factors ARC1, CKA2 and GUS1. By the alkylating agent methyl methanesulfonate (MMS). Present with 861 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.