Serine/threonine-protein kinase involved in transcription regulation, apoptosis and steroidogenic gene expression. Phosphorylates JUN and RUNX2. Seems to negatively regulate apoptosis by promoting FADD phosphorylation. Enhances androgen receptor-mediated transcription. May act as a transcriptional corepressor for NK homeodomain transcription factors. The phosphorylation of NR5A1 activates SF1 leading to increased steroidogenic gene expression upon cAMP signaling pathway stimulation. In osteoblasts, supports transcription activation: phosphorylates RUNX2 that synergizes with SPEN/MINT to enhance FGFR2-mediated activation of the osteocalcin FGF-responsive element (OCFRE). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with Nkx1-2. Interacts with FAS and DAXX. Probably part of a complex consisting of HIPK3, FAS and FADD. Interacts with and stabilizes ligand-bound androgen receptor (AR) (By similarity). Interacts with UBL1/SUMO-1. Binds to NR5A1/SF1, SPEN/MINT and RUNX2. Overexpressed in multidrug resistant cells. Highly expressed in heart and skeletal muscle, and at lower levels in placenta, pancreas, brain, spleen, prostate, thymus, testis, small intestine, colon and leukocytes. Not found in liver and lung. Autophosphorylated, but autophosphorylation is not required for catalytic activity. May be sumoylated. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. HIPK subfamily.