Transcriptional regulation of hypoxia-inducible factor 1alpha by HIPK2 suggests a novel mechanism to restrain tumor growth.
HIPK2 has been implicated in restraining tumor progression by more than one mechanism, involving both its catalytic and transcriptional co-repressor functions. Starting from the finding that HIPK2 knockdown by RNA-interference (HIPK2i) induced significant up-regulation of HIF-1alpha mRNA and of its target VEGF in tumor cells, we evaluated the role of HIPK2 in transcriptional regulation of HIF-1alpha. We found that HIPK2 overexpression downmodulated both HIF-1alpha reporter activity and mRNA levels and showed that HIPK2 was bound in vivo to the HIF-1alpha promoter likely in a multiprotein co-repressor complex with histone deacetylase 1 (HDAC1). Thus, the HIF-1alpha promoter was strongly acetylated following HIPK2 knockdown. The HIF-1alpha-dependent VEGF transcription was evaluated by co-transfection of a dominant negative (DN) construct of HIF-1alpha that inhibited VEGF reporter activity induced by HIPK2 knockdown. HIF-1alpha and VEGF up-regulation in HIPK2i cells correlated with increased vascularity of tumor xenografts in vivo and tube formation in HUVEC in vitro. These findings provide the first evidence of HIPK2-mediated transcriptional regulation of HIF-1alpha that might play a critical role in VEGF expression.
Nardinocchi
Lavinia
L
Molecular Oncogenesis Laboratory, Regina Elena Cancer Institute, (00158) Rome, Italy.
Puca
Rosa
R
Guidolin
Diego
D
Belloni
Anna S
AS
Bossi
Gianluca
G
Michiels
Carine
C
Sacchi
Ada
A
Onisto
Maurizio
M
D'Orazi
Gabriella
G
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D042002:Chromatin Assembly and Disassembly / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D009369:Neoplasms / Q000098:blood supply / Q000201:enzymology / Q000235:genetics* / Q000473:pathology*; D009389:Neovascularization, Pathologic / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
D002352:Carrier Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012097:Repressor Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C115114:HIPK2 protein, human; D017346:Protein Serine-Threonine Kinases