Regulation of ferrochelatase gene expression by hypoxia.
Ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, catalyzes the insertion of iron into protoporphyrin to form heme. This pathway provides heme for hemoglobin and other essential hemoproteins. The regulatory role of oxygen in the pathway has not been clearly established. In this study, we examined whether FECH gene expression is upregulated during hypoxia by a mechanism which involves the hypoxia-inducible factor 1 (HIF-1). Two HIF-1 binding motifs were identified within the -150 bp FECH minimal promoter sequence. Exposure of HEL, K562, and Hep-G2 cells to hypoxia for 18 hours resulted in a significant increase in FECH mRNA expression (p < 0.05). Hypoxia also transactivated the minimal promoter for the FECH gene in the cells. Transient co-expression of wild-type HIF-1alpha or a dominant negative HIF-1alpha with the FECH minimal promoter luciferase construct stimulated or blocked FECH promoter activity, respectively. Expression of the von Hippel-Lindau (VHL) tumor suppressor factor blocked the expression of both FECH mRNA and HIF-1alpha protein during normoxic culture of renal carcinoma cell line (RCC4). The results suggest that the FECH gene is a target for HIF-1 during hypoxia.
Department of Medicine, Liver Center, University of Alabama at Birmingham, 35294-0005, USA.
Yunying L
YL
Liu
Sonny O
SO
Ang
Douglas A
DA
Weigent
Josef T
JT
Prchal
Joseph R
JR
Bloomer
D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005294:Ferrochelatase / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000503:physiopathology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D051794:Von Hippel-Lindau Tumor Suppressor Protein
D017931:DNA Primers; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D008156:Luciferases; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D005294:Ferrochelatase; C497446:VHL protein, human