Hepatitis B virus X protein enhances transcriptional activity of hypoxia-inducible factor-1alpha through activation of mitogen-activated protein kinase pathway.
Hepatitis B virus X protein (HBx) of the hepatitis B virus was strongly implicated in angiogenesis and metastasis during hepatocarcinogenesis. Here, we explored the possibility of cross-talk between HBx and hypoxia-inducible factor-1alpha (HIF-1alpha), a potent transcriptional inducer of angiogenic factors. First, we showed that stability of HIF-1alpha protein was increased by HBx in HBx-inducible Chang liver cells as well as in transient HBx expression system of non-hepatic cells. Immunofluorescence studies revealed that the HBx-induced HIF-1alpha was partially translocated into the nucleus in majority of cells while additional CoCl2-induced hypoxic condition caused complete nuclear translocation. Second, HBx induced both phosphorylation of HIF-1alpha and activation of p42/p44 mitogen-activated protein kinases (MAPKs), which were synergistically enhanced in the presence of CoCl2. Furthermore, HBx enhanced transcriptional activity of HIF-1alpha in the reporter genes encoding hypoxia response element or VEGF promoter. Either treatment of MEK inhibitor PD98059 or coexpression of dominant-negative MAPK mutants abolished the HBx-induced transcriptional activity and protein stability as well as nuclear translocation of HIF-1alpha, suggesting that HBx activates HIF-1alpha through MAPK pathway. Third, the association of HIF-1alpha with von Hippel-Lindau was decreased but the association with CREB-binding protein was enhanced in the presence of HBx, suggesting the molecular mechanism by which HBx enhances the protein stability and transactivation function of HIF-1alpha. Finally, we demonstrated that expression of HIF-1alpha and vascular endothelial growth factor was increased in the liver of HBx-transgenic mice, suggesting that the cross-talk between HIF-1alpha and HBx may lead to transcriptional activation of HIF-1alpha target genes, which play a critical role in hepatocarcinogenesis.
Yoo
Young-Gun
YG
Department of Bioscience and Biotechnology, Sejong University, Seoul 140-747, Korea.
Oh
Seung Hyun
SH
Park
Eun Sook
ES
Cho
Hyeseong
H
Lee
Naery
N
Park
Hyunsung
H
Kim
Dae Kyong
DK
Yu
Dae-Yeul
DY
Seong
Je Kyung
JK
Lee
Mi-Ock
MO
D021581:Active Transport, Cell Nucleus; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D016228:Endothelial Growth Factors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008025:Ligases / Q000378:metabolism; D008222:Lymphokines / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D054334:Viral Regulatory and Accessory Proteins; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000077191:Wortmannin
D000730:Androstadienes; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D005419:Flavonoids; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D003035:Cobalt; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D008025:Ligases; C497446:VHL protein, human; C018021:cobaltous chloride; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin