Casein kinases are operationally defined by their preferential utilization of acidic proteins such as caseins as substrates (Probable). Participates in Wnt signaling (PubMed:12556519, PubMed:23413191). Phosphorylates DVL1 (PubMed:12556519). Phosphorylates DVL2 (PubMed:23413191). Phosphorylates NEDD9/HEF1 (By similarity). Central component of the circadian clock (PubMed:16790549). In balance with PP1, determines the circadian period length, through the regulation of the speed and rhythmicity of PER1 and PER2 phosphorylation (PubMed:15917222, PubMed:16790549). Controls PER1 and PER2 nuclear transport and degradation (By similarity). Inhibits cytokine-induced granuloytic differentiation (PubMed:15070676). {ECO:0000250|UniProtKB:Q9JMK2, ECO:0000269|PubMed:12556519, ECO:0000269|PubMed:15070676, ECO:0000269|PubMed:15917222, ECO:0000269|PubMed:16790549, ECO:0000269|PubMed:23413191, ECO:0000305|PubMed:7797465}. This is the function of CSNK1E (casein kinase 1 epsilon, ENSG00000213923).