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Catalytic domain of the Serine/Threonine Kinase, Homeodomain-Interacting Protein Kinase 2 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. HIPK2, the most studied HIPK, is a coregulator of many transcription factors and cofactors including homeodomain proteins (Nkx and HOX families), Smad1-4, Pax6, c-Myb, AML1, the histone acetyltransferase p300, and the tumor repressor p53, among others. It regulates gene transcription during development and in DNA damage response (DDR), and mediates cell processes such as apoptosis, survival, differentiation, and proliferation. HIPK2 mediates apoptosis by phosphorylating and activating p53 during DDR, resulting in the activation of apoptotic genes. In the absence of p53, HIPK2 targets the anti-apoptotic corepressor C-terminal binding protein (CtBP), leading to CtBP's degradation and the promotion of apoptosis. HIPKs, originally identified by their ability to bind homeobox factors, are nuclear proteins containing catalytic kinase and homeobox-interacting domains as well as a PEST region overlapping with the speckle-retention signal (SRS). The HIPK2 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",