title: HIPK2 regulates transforming growth factor-beta-induced c-Jun NH(2)-terminal kinase activation and apoptosis in human hepatoma cells.
abstract: Homeodomain-interacting protein kinase 2 (HIPK2) is a serine/threonine kinase involved in transcriptional regulation and apoptosis. Here we demonstrate that HIPK2 regulates transforming growth factor (TGF) beta-induced c-Jun NH(2)-terminal kinase (JNK) activation and apoptosis. HIPK2 colocalizes with Daxx, a protein acting in TGF-beta-induced JNK activation and apoptosis, in promyelocytic leukemia (PML) nuclear bodies, and triggers PML-nuclear body disruption and release of Daxx. HIPK2 interacts in vitro and in vivo via its kinase domain with Daxx, and a fraction of Daxx coprecipitates with HIPK2 under physiological conditions. Moreover, overexpression of HIPK2 leads to Daxx phosphorylation, and ectopic expression of HIPK2 activates the JNK signaling pathway, which is enhanced by coexpression of Daxx. HIPK2 signals to JNK via a pathway using Daxx and the mitogen-activated protein kinase kinases MKK4/SEK1 and MKK7. Ectopic expression of HIPK2 and Daxx potentiates TGF-beta-induced apoptosis in human p53-deficient hepatocellular carcinoma cells. Finally, we demonstrate that knockdown of endogenous HIPK2 using RNA interference inhibits TGF-beta-induced JNK activation and apoptosis. Taken together, our findings indicate that HIPK2 participates in the TGF-beta signaling pathway leading to JNK activation and apoptosis.
authors.affiliation: Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie an der Universität Hamburg, Hamburg, Germany. thomas.hoffmann@hpi.uni-hamburg.de
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Hofmann
authors.forename: Nicole
authors.initials: N
authors.lastname: Stollberg
authors.forename: M Lienhard
authors.initials: ML
authors.lastname: Schmitz
authors.forename: Hans
authors.initials: H
authors.lastname: Will
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D056970:Co-Repressor Proteins; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism; D008113:Liver Neoplasms / Q000201:enzymology* / Q000473:pathology; D048669:MAP Kinase Kinase 6; D048688:MAP Kinase Kinase 7; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D016212:Transforming Growth Factor beta; C115114:HIPK2 protein, human; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048669:MAP Kinase Kinase 6; D048688:MAP Kinase Kinase 7; C482566:MAP2K6 protein, human; C482569:MAP2K7 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases