CITED2 mediates the paradoxical responses of HIF-1alpha to proteasome inhibition.
Hypoxia-inducible factor-1alpha (HIF-1alpha) is destabilized via the ubiquitin-proteasome system. Thus HIF-1alpha expression is robustly upregulated by proteasome inhibition, but paradoxically its activity is reduced. In the present study, we investigated the mechanism underlying the paradoxical response of HIF-1alpha to proteasome inhibition. In both Hep3B and HEK293 cells, a proteasome inhibitor MG132 noticeably attenuated hypoxic induction of erythropoietin and VEGF mRNAs. MG132 inactivated HIF-1alpha C-terminal transactivation domain (CAD), independently of factor inhibiting HIF-1 (FIH) and inhibited p300 recruitment by HIF-1alpha. We next tested the possibility that CITED2 is involved in the HIF-1 inactivation. CITED2 was found to be degraded via the ubiquitin-proteasome system and thus was stabilized by proteasome inhibition. Both the activity and the p300 binding of HIF-1alpha were inhibited by CITED2 expression and recovered by CITED2 siRNA in the presence of MG132. These results suggest that CITED2 is stabilized by proteasome inhibition and inactivates HIF-1 by interfering with the HIF-1alpha-p300 interaction. This may be an important mode-of-action for proteasome inhibition-based cancer therapy.
Shin
D H
DH
Department of Pharmacology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul, Korea.
Li
S H
SH
Chun
Y-S
YS
Huang
L E
LE
Kim
M-S
MS
Park
J-W
JW
D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050881:E1A-Associated p300 Protein / Q000235:genetics / Q000378:metabolism; D004921:Erythropoietin / Q000235:genetics; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008113:Liver Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D006899:Mixed Function Oxygenases; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
C486381:CITED2 protein, human; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007976:Leupeptins; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D025801:Ubiquitin; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D004921:Erythropoietin; D006899:Mixed Function Oxygenases; C439790:HIF1AN protein, human; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde