A dominant-negative isoform lacking exons 11 and 12 of the human hypoxia-inducible factor-1alpha gene.
Hypoxia-inducible factor-1alpha (HIF-1alpha), a member of the transcription family characterized by a basic helix-loop-helix (bHLH) domain and a PAS domain, regulates the transcription of hypoxia-inducible genes involved in erythropoiesis, vascular remodelling and glucose/energy metabolism. It contains bHLH/PAS domains in the N-terminal half, and a nuclear localization signal (NLS) and two ... transactivation domains (TADs) in the C-terminal half. It also has an oxygen-dependent degradation (ODD) domain, which is required to degrade HIF-1alpha protein by the ubiquitin-proteasome pathway. In this study, we identified a new alternatively spliced variant of human HIF-1alpha mRNA, which lacked both exons 11 and 12, producing a frame shift and giving a shorter form of HIF-1alpha. In the corresponding protein, a part of the ODD domain, both TADs and the C-terminal NLS motif were missing. Expression of endogenous HIF-1alpha variant protein was identified using immunoprecipitation and immunoblotting methods. The expressed HIF-1alpha variant exhibited neither the activity of transactivation nor hypoxia-induced nuclear translocation. In contrast with HIF-1alpha, the variant was strikingly stable in normoxic conditions and not up-regulated to such an extent by hypoxia, cobalt ions or desferrioxamine. It was also demonstrated that the HIF-1alpha variant competed with endogenous HIF-1alpha and suppressed HIF-1 activity, resulting in the down-regulation of mRNA expression of hypoxia-inducible genes. The association of the variant and arylhydrocarbon receptor nuclear translocator in the cytoplasm may be related to the inhibition of HIF-1 activity. It is assumed that this isoform preserves the balance between aerobic and anaerobic metabolism by counteracting the overaction of HIF-1alpha.
Mesh Terms:
Alternative Splicing, Animals, Aryl Hydrocarbon Receptor Nuclear Translocator, Base Sequence, Blotting, Western, Cell Line, Cloning, Molecular, DNA Primers, DNA-Binding Proteins, Electrophoretic Mobility Shift Assay, Exons, Gene Expression Regulation, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Mice, Microscopy, Fluorescence, Precipitin Tests, Protein Isoforms, RNA, Messenger, Receptors, Aryl Hydrocarbon, Reverse Transcriptase Polymerase Chain Reaction, Transcription Factors
Alternative Splicing, Animals, Aryl Hydrocarbon Receptor Nuclear Translocator, Base Sequence, Blotting, Western, Cell Line, Cloning, Molecular, DNA Primers, DNA-Binding Proteins, Electrophoretic Mobility Shift Assay, Exons, Gene Expression Regulation, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Mice, Microscopy, Fluorescence, Precipitin Tests, Protein Isoforms, RNA, Messenger, Receptors, Aryl Hydrocarbon, Reverse Transcriptase Polymerase Chain Reaction, Transcription Factors
Biochem. J.
Date: Feb. 15, 2002
PubMed ID: 11829741
View in: Pubmed Google Scholar
Download Curated Data For This Publication
170783
Switch View:
- Interactions 1