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Mol. Cell. Biol., 09 1996, 4604-4613, Vol 16, No. 9
JA Forsythe, BH Jiang, NV Iyer, F Agani, SW Leung, RD Koos and GL Semenza
Expression of vascular endothelial growth factor (VEGF) is induced in cells
exposed to hypoxia or ischemia. Neovascularization stimulated by VEGF
occurs in several important clinical contexts, including myocardial
ischemia, retinal disease, and tumor growth. Hypoxia- inducible factor 1
(HIF-1) is a heterodimeric basic helix-loop-helix protein that activates
transcription of the human erythropoietin gene in hypoxic cells. Here we
demonstrate the involvement of HIF-1 in the activation of VEGF
transcription. VEGF 5'-flanking sequences mediated transcriptional
activation of reporter gene expression in hypoxic Hep3B cells. A 47-bp
sequence located 985 to 939 bp 5' to the VEGF transcription initiation site
mediated hypoxia-inducible reporter gene expression directed by a simian
virus 40 promoter element that was otherwise minimally responsive to
hypoxia. When reporters containing VEGF sequences, in the context of the
native VEGF or heterologous simian virus 40 promoter, were cotransfected
with expression vectors encoding HIF-1alpha and HIF-1beta (ARNT [aryl
hydrocarbon receptor nuclear translocator]), reporter gene transcription
was much greater in both hypoxic and nonhypoxic cells than in cells
transfected with the reporter alone. A HIF-1 binding site was demonstrated
in the 47-bp hypoxia response element, and a 3-bp substitution eliminated
the ability of the element to bind HIF-1 and to activate transcription in
response to hypoxia and/or recombinant HIF-1. Cotransfection of cells with
an expression vector encoding a dominant negative form of HIF- 1alpha
inhibited the activation of reporter transcription in hypoxic cells in a
dose-dependent manner. VEGF mRNA was not induced by hypoxia in mutant cells
that do not express the HIF-1beta (ARNT) subunit. These findings implicate
HIF-1 in the activation of VEGF transcription in hypoxic cells.
Copyright © 1996, American Society for Microbiology
Activation of vascular endothelial growth factor gene transcription by hypoxia-inducible factor 1
Department of Physiology, University of Maryland School of Medicine, Baltimore, 21201, USA.
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