Adapter protein involved in protein degradation by interacting with COP1 ubiquitin ligase (PubMed:27041596). The COP1-binding motif is masked by autoinhibitory interactions with the protein kinase domain (PubMed:26455797). Serves to alter COP1 substrate specificity by directing the activity of COP1 toward CEBPA (PubMed:27041596). Binds selectively the recognition sequence of CEBPA (PubMed:26455797). Regulates myeloid cell differentiation by altering the expression of CEBPA in a COP1-dependent manner (By similarity). Controls macrophage, eosinophil and neutrophil differentiation via the COP1-binding domain (By similarity). Interacts with MAPK kinases and regulates activation of MAP kinases, but has no kinase activity (PubMed:15299019, PubMed:26455797). Monomer (PubMed:26455797). Interacts (via protein kinase domain) with CEBPA (PubMed:20410507, PubMed:26455797). Interacts with COP1 (PubMed:20410507, PubMed:27041596). Expressed in most human tissues with the highest levels in skeletal muscle, thyroid gland, pancreas, peripheral blood leukocytes, and bone marrow. The protein kinase active site is incompatible with ATP binding and is inactive (PubMed:26455797). The C-terminus (351-372) is required for interaction with COP1 (PubMed:27041596). The COP1-binding motif (355-360) is required for regulation activity (By similarity). Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. Tribbles subfamily.