The HUNK (hormonally upregulated Neu-associated kinase) protein, also designated MAK-V in mouse, has been identified as a novel SNF1-related serine/threonine kinase. The human HUNK gene localizes to chromosome 21q22 and encodes a protein with nucleocytoplasmic distribution and localizes to the centrosome. Overexpression of the HUNK protein associates with approximately 50% of breast carcinomas, and may provide diagnostic-prognostic value as a molecular marker. Serine/threonine-protein kinase SNF1-like kinase 2 (SIK) phosphorylates Ser-794 of IRS1 in insulin-stimulated adipocytes, which may modulate the efficiency of insulin signal transduction. SIK is activated by phosphorylation on Thr-175 by STK11 in complex with STE20-related adapter-α and CAB39.