Serine/threonine-protein kinase involved in transcription regulation, p53/TP53-mediated cellular apoptosis and regulation of the cell cycle. Acts as a corepressor of several transcription factors, including SMAD1 and POU4F1/Brn3a and probably NK homeodomain transcription factors. Phosphorylates PDX1, ATF1, PML, p53/TP53, CREB1, CTBP1, CBX4, RUNX1, EP300, CTNNB1, HMGA1 and ZBTB4. Inhibits cell growth and promotes apoptosis through the activation of p53/TP53 both at the transcription level and at the protein level (by phosphorylation and indirect acetylation). The phosphorylation of p53/TP53 may be mediated by a p53/TP53-HIPK2-AXIN1 complex. Involved in the response to hypoxia by acting as a transcriptional co-suppressor of HIF1A. Mediates transcriptional activation of TP73. In response to TGFB, cooperates with DAXX to activate JNK. Negative regulator through phosphorylation and subsequent proteasomal degradation of CTNNB1 and the antiapoptotic factor CTBP1. In the Wnt/beta-catenin signaling pathway acts as an intermediate kinase between MAP3K7/TAK1 and NLK to promote the proteasomal degradation of MYB. Phosphorylates CBX4 upon DNA damage and promotes its E3 SUMO-protein ligase activity. Activates CREB1 and ATF1 transcription factors by phosphorylation in response to genotoxic stress. In response to DNA damage, stabilizes PML by phosphorylation. PML, HIPK2 and FBXO3 may act synergically to activate p53/TP53-dependent transactivation. Promotes angiogenesis, and is involved in erythroid differentiation, especially during fetal liver erythropoiesis. Phosphorylation of RUNX1 and EP300 stimulates EP300 transcription regulation activity. Triggers ZBTB4 protein degradation in response to DNA damage. Modulates HMGA1 DNA-binding affinity. In response to high glucose, triggers phosphorylation-mediated subnuclear localization shifting of PDX1. Involved in the regulation of eye size, lens formation and retinal lamination during late embryogenesis. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with CREB1, SIAH1, WSB1, CBX4, TRADD, p53/TP53, TP73, TP63, CREBBP, DAXX, P53DINP1, SKI, SMAD1, SMAD2 and SMAD3, but not SMAD4. Interacts with ATF1, PML, RUNX1, EP300, NKX1-2, NKX2-5, UBE2I, HMGA1, CTBP1, AXIN1, NLK, MYB, POU4F1, POU4F2, POU4F3, UBE2I, UBL1 and ZBTB4. Probably part of a complex consisting of p53/TP53, HIPK2 and AXIN1. Interacts with SP100; positively regulates TP53-dependent transcription. Interacts with SUMO1P1/SUMO5 (PubMed:27211601). (Microbial infection) Interacts with Hantaan hantavirus nucleoprotein. (Microbial infection) Interacts with Seoul hantavirus nucleoprotein. Concentrated in PML/POD/ND10 nuclear bodies. Small amounts are cytoplasmic. Experimental confirmation may be lacking for some isoforms. Highly expressed in heart, muscle and kidney. Weakly expressed in a ubiquitous way. Down-regulated in several thyroid and breast tumors. Unstable in unstressed cells but stabilized upon DNA damage. Induced by UV irradiation and other genotoxic agents (adriamycin ADR, cisplatin CDDP, etoposide, IR, roscovitin), thus triggering p53/TP53 apoptotic response. Consistutively negatively regulated by SIAH1 and WSB1 through proteasomal degradation. This negative regulation is impaired upon genotoxic stress. Repressed upon hypoxia (often associated with tumors), through MDM2- (an E3 ubiquitin ligases) mediated proteasomal degradation, thus inactivating p53/TP53 apoptotic response. This hypoxia repression is reversed by zinc. The stabilization mediated by DNA damage requires the damage checkpoint kinases ATM and ATR. Autophosphorylation at Tyr-361 in the activation loop activates the kinase and promotes nuclear localization. Sumoylated. When conjugated it is directed to nuclear speckles. Desumoylated by SENP1 (By similarity). Sumoylation on Lys-32 is promoted by the E3 SUMO-protein ligase CBX4. Ubiquitinated by FBXO3, WSB1 and SIAH1, leading to rapid proteasome-dependent degradation. The degradation mediated by FBXO3, but not ubiquitination, is prevented in the presence of PML. The degradation mediated by WSB1 and SIAH1 is reversibly reduced upon DNA damage. Cleaved at Asp-923 and Asp-984 by CASP6 in a p53/TP53-dependent manner. The cleaved form lacks the autoinhibitory C-terminal domain (AID), resulting in a hyperactive kinase, which potentiates p53/TP53 Ser-46 phosphorylation and subsequent activation of the cell death machinery. Interesting targets for cancer therapy. HIPK2 deregulation would end up in a multifactorial response leading to tumor chemoresistance by affecting p53/TP53 activity on one hand and to angiogenesis and cell proliferation by affecting HIF1A activity on the other hand. May provide important insights in the process of tumor progression, and may also serve as the crucial point in the diagnostic and therapeutical aspects of cancer. Tumor treatment may potential be improved by zinc supplementation in combination with chemotherapy to address hypoxia (PubMed:20514025). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. HIPK subfamily.