Casein kinases are operationally defined by their preferential utilization of acidic proteins such as caseins as substrates. Can phosphorylate a large number of proteins. Negative regulator of wg signaling (PubMed:22095083). Phosphorylates arm directly or indirectly and stimulates its degradation which prevents inappropriate wg signaling (PubMed:11955436, PubMed:11927557, PubMed:22095083). Phosphorylates smo which promotes its accumulation at the cell surface and its signaling activity in response to hh (PubMed:15616566). Together with dco, regulates proteolytic processing of ci by phosphorylating it which promotes its binding to slmb, the F-box recognition component of the SCF(slmb) E3 ubiquitin-protein ligase required for ci processing (PubMed:16326393). Inhibits condensin II interphase activity by promoting degradation of the Cap-H2 regulatory subunit and limiting the levels of chromatin-bound Cap-H2 which regulates interphase chromosome organization (PubMed:25723539). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activity increases following DNA damage. Interacts with cos. Levels in the nucleus are significantly increased after DNA damage. Expressed during early embryogenesis and in adult females (at protein level). Phosphorylated. The dephosphorylated kinase is active in the cytoplasm while the active kinase in the nucleus is phosphorylated. Belongs to the protein kinase superfamily. CK1 Ser/Thr protein kinase family. Casein kinase I subfamily. Truncated N-terminus.