HIPK4 (Homeodomain-interacting protein kinase 4) is a 616 amino acid protein that localizes to the cytoplasm and exists as two isoforms that are produced by alternative splicing events. Like other members of the HIPK family, HIPK4 functions as a protein kinase that catalyzes the ATP-dependent phosphorylation of target proteins and is thought to act as a corepressor of target transcription factors.