Hypoxia-inducible factor-1 mediates transcriptional activation of the heme oxygenase-1 gene in response to hypoxia.
Exposure of rats to hypoxia (7% O2) markedly increased the level of heme oxygenase-1 (HO-1) mRNA in several tissues. Accumulation of HO-1 transcripts was also observed after exposure of rat aortic vascular smooth muscle (VSM) cells to 1% O2, and this induction was dependent on gene transcription. Activation of the mouse HO-1 gene by all agents thus far tested is mediated by two 5'-enhancer sequences, SX2 and AB1, but neither fragment was responsive to hypoxia in VSM cells. Hypoxia-dependent induction of the chloramphenicol acetyltransferase (CAT) reporter gene was mediated by a 163-bp fragment located approximately 9.5 kilobases upstream of the transcription start site. This fragment contains two potential binding sites for hypoxia-inducible factor 1 (HIF-1). A role for HIF-1 in HO-1 gene regulation was established by the following observations: 1) HIF-1 specifically bound to an oligonucleotide spanning these sequences, 2) mutation of these sequences abolished HIF-1 binding and hypoxia-dependent gene activation in VSM cells, 3) hypoxia increased HIF-1alpha and HIF-1beta protein levels in VSM cells, and 4) hypoxia-dependent HO-1 mRNA accumulation was not observed in mutant hepatoma cells lacking HIF-1 DNA-binding activity. Taken together, these data demonstrate that hypoxia induces HO-1 expression in animal tissues and cell cultures and implicate HIF-1 in this response.
Lee
P J
PJ
Division of Pulmonary and Critical Care, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Jiang
B H
BH
Chin
B Y
BY
Iyer
N V
NV
Alam
J
J
Semenza
G L
GL
Choi
A M
AM
D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D003609:Dactinomycin / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D018257:Helix-Loop-Helix Motifs; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D000860:Hypoxia / Q000201:enzymology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051379:Mice; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D009687:Nuclear Proteins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015183:Restriction Mapping; D014157:Transcription Factors / Q000494:pharmacology*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C497443:Hif1a protein, mouse; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D003609:Dactinomycin; D006419:Heme Oxygenase (Decyclizing)