Induction of endothelial PAS domain protein-1 by hypoxia: characterization and comparison with hypoxia-inducible factor-1alpha.
TL;DR: Functional studies in a mutant cell line expressing neither HIF-1alpha nor EPAS-1 confirmed that both proteins interact with hypoxically responsive targets, but suggest target specificity with greater EPas-1 transactivation of the VEGF promoter than the LDH-A promoter.
About: This article is published in Blood.The article was published on 1998-10-01 and is currently open access. It has received 661 citations till now. The article focuses on the topics: Aryl hydrocarbon receptor nuclear translocator & Transactivation.
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TL;DR: It is shown that the interaction between human pVHL and a specific domain of the HIF-1α subunit is regulated through hydroxylation of a proline residue by an enzyme the authors have termed Hif-α prolyl-hydroxylase (HIF-PH).
Abstract: Hypoxia-inducible factor (HIF) is a transcriptional complex that plays a central role in the regulation of gene expression by oxygen. In oxygenated and iron replete cells, HIF-alpha subunits are rapidly destroyed by a mechanism that involves ubiquitylation by the von Hippel-Lindau tumor suppressor (pVHL) E3 ligase complex. This process is suppressed by hypoxia and iron chelation, allowing transcriptional activation. Here we show that the interaction between human pVHL and a specific domain of the HIF-1alpha subunit is regulated through hydroxylation of a proline residue (HIF-1alpha P564) by an enzyme we have termed HIF-alpha prolyl-hydroxylase (HIF-PH). An absolute requirement for dioxygen as a cosubstrate and iron as cofactor suggests that HIF-PH functions directly as a cellular oxygen sensor.
5,186 citations
TL;DR: It is indicated that the interaction between HIF-1 and pVHL is iron dependent, and that it is necessary for the oxygen-dependent degradation of HIF α-subunits, which may underlie the angiogenic phenotype of VHL-associated tumours.
Abstract: Hypoxia-inducible factor-1 (HIF-1) has a key role in cellular responses to hypoxia, including the regulation of genes involved in energy metabolism, angiogenesis and apoptosis. The alpha subunits of HIF are rapidly degraded by the proteasome under normal conditions, but are stabilized by hypoxia. Cobaltous ions or iron chelators mimic hypoxia, indicating that the stimuli may interact through effects on a ferroprotein oxygen sensor. Here we demonstrate a critical role for the von Hippel-Lindau (VHL) tumour suppressor gene product pVHL in HIF-1 regulation. In VHL-defective cells, HIF alpha-subunits are constitutively stabilized and HIF-1 is activated. Re-expression of pVHL restored oxygen-dependent instability. pVHL and HIF alpha-subunits co-immunoprecipitate, and pVHL is present in the hypoxic HIF-1 DNA-binding complex. In cells exposed to iron chelation or cobaltous ions, HIF-1 is dissociated from pVHL. These findings indicate that the interaction between HIF-1 and pVHL is iron dependent, and that it is necessary for the oxygen-dependent degradation of HIF alpha-subunits. Thus, constitutive HIF-1 activation may underlie the angiogenic phenotype of VHL-associated tumours. The pVHL/HIF-1 interaction provides a new focus for understanding cellular oxygen sensing.
4,845 citations
TL;DR: The role of HIF in developmental, adaptive and neoplastic angiogenesis, and the implications of oncogenic activation of extensive, physiologically interconnected hypoxia pathways for the tumor phenotype are discussed.
Abstract: The regulation of angiogenesis by hypoxia is an important component of homeostatic mechanisms that link vascular oxygen supply to metabolic demand. Molecular characterization of angiogenic pathways, identification of hypoxia-inducible factor (HIF) as a key transcriptional regulator of these molecules, and the definition of the HIF hydoxylases as a family of dioxygenases that regulate HIF in accordance with oxygen availability have provided new insights into this process. Here we review these findings, and the role of HIF in developmental, adaptive and neoplastic angiogenesis. We also discuss the implications of oncogenic activation of extensive, physiologically interconnected hypoxia pathways for the tumor phenotype.
2,328 citations
TL;DR: HIF-1 appears to function as a master regulator of O2 homeostasis that plays essential roles in cellular and systemic physiology, development, and pathophysiology.
Abstract: Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic-helix-loop-helix-PAS transcription factor consisting of HIF-1 alpha and HIF-1 beta subunits. HIF-1 alpha expression and HIF-1 transcriptional activity increase exponentially as cellular O2 concentration is decreased. Several dozen target genes that are transactivated by HIF-1 have been identified, including those encoding erythropoietin, glucose transporters, glycolytic enzymes, and vascular endothelial growth factor. The products of these genes either increase O2 delivery or allow metabolic adaptation to reduced O2 availability. HIF-1 is required for cardiac and vascular development and embryonic survival. In fetal and postnatal life, HIF-1 is required for a variety of physiological responses to chronic hypoxia. HIF-1 expression is increased in tumor cells by multiple mechanisms and may mediate adaptation to hypoxia that is critical for tumor progression. HIF-1 thus appears to function as a master regulator of O2 homeostasis that plays essential roles in cellular and systemic physiology, development, and pathophysiology.
1,912 citations
TL;DR: HIF-1 appears to play a key role in the pathophysiology of cancer, cardiovascular disease, and chronic lung disease, which represent the major causes of mortality among industrialized societies.
Abstract: All organisms can sense O2 concentration and respond to hypoxia with adaptive changes in gene expression. The large body size of mammals necessitates the development of multiple complex physiological systems to ensure adequate O2 delivery to all cells under normal conditions. The transcriptional regulator hypoxia-inducible factor 1 (HIF-1) is an essential mediator of O2homeostasis. HIF-1 is required for the establishment of key physiological systems during development and their subsequent utilization in fetal and postnatal life. HIF-1 also appears to play a key role in the pathophysiology of cancer, cardiovascular disease, and chronic lung disease, which represent the major causes of mortality among industrialized societies. Genetic or pharmacological modulation of HIF-1 activity in vivo may represent a novel therapeutic approach to these disorders.
1,711 citations
Cites background from "Induction of endothelial PAS domain..."
...Despite the prominent expression of HIF-2a in the vascular endothelium of wild-type mice, Epas12/2 mice have no obvious vascular defects, suggesting that HIF-1a expression in these cells (75) may be sufficient for normal development....
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...1) are highly conserved in HIF-2a (49, 67, 73)....
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...However, the role of HIF-2a in vascular development within specific organs, such as the lung (11), warrants further study....
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...Together, these findings suggest the possibility that HIF-1a (as well as HIF-2a, HIF-3a, and other class II bHLH-PAS proteins) may bind a cofactor through which the biological activity of the transcription factor could be modulated....
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...Renal carcinoma cell lines, which lack expression of the von Hipple-Lindau (VHL) tumor suppressor protein, maximally express HIF-1a and HIF-2a under nonhypoxic conditions and O2-regulated expression is restored in cells that have been transfected with a VHL expression vector (47)....
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TL;DR: Hypoxia-inducible factor 1 (HIF-1) is found in mammalian cells cultured under reduced O2 tension and is necessary for transcriptional activation mediated by the erythropoietin gene enhancer in hypoxic cells.
Abstract: Hypoxia-inducible factor 1 (HIF-1) is found in mammalian cells cultured under reduced O2 tension and is necessary for transcriptional activation mediated by the erythropoietin gene enhancer in hypoxic cells. We show that both HIF-1 subunits are basic-helix-loop-helix proteins containing a PAS domain, defined by its presence in the Drosophila Per and Sim proteins and in the mammalian ARNT and AHR proteins. HIF-1 alpha is most closely related to Sim. HIF-1 beta is a series of ARNT gene products, which can thus heterodimerize with either HIF-1 alpha or AHR. HIF-1 alpha and HIF-1 beta (ARNT) RNA and protein levels were induced in cells exposed to 1% O2 and decayed rapidly upon return of the cells to 20% O2, consistent with the role of HIF-1 as a mediator of transcriptional responses to hypoxia.
5,729 citations
TL;DR: A functionally tripartite, 50-nt hypoxia-inducible enhancer which binds several nuclear factors, one of which is induced by Hypoxia via de novo protein synthesis.
Abstract: We have identified a 50-nucleotide enhancer from the human erythropoietin gene 3'-flanking sequence which can mediate a sevenfold transcriptional induction in response to hypoxia when cloned 3' to a simian virus 40 promoter-chloramphenicol acetyltransferase reporter gene and transiently expressed in Hep3B cells Nucleotides (nt) 1 to 33 of this sequence mediate sevenfold induction of reporter gene expression when present in two tandem copies compared with threefold induction when present in a single copy, suggesting that nt 34 to 50 bind a factor which amplifies the induction signal DNase I footprinting demonstrated binding of a constitutive nuclear factor to nt 26 to 48 Mutagenesis studies revealed that nt 4 to 12 and 19 to 23 are essential for induction, as substitutions at either site eliminated hypoxia-induced expression Electrophoretic mobility shift assays identified a nuclear factor which bound to a probe spanning nt 1 to 18 but not to a probe containing a mutation which eliminated enhancer function Factor binding was induced by hypoxia, and its induction was sensitive to cycloheximide treatment We have thus defined a functionally tripartite, 50-nt hypoxia-inducible enhancer which binds several nuclear factors, one of which is induced by hypoxia via de novo protein synthesis
2,523 citations
TL;DR: The identification of an oxygen-dependent degradation (ODD) domain within HIF-1alpha that controls its degradation by the ubiquitin-proteasome pathway is reported and may provide a means of controlling gene expression by changes in oxygen tension.
Abstract: Hypoxia induces a group of physiologically important genes such as erythropoietin and vascular endothelial growth factor. These genes are transcriptionally up-regulated by hypoxia-inducible factor 1 (HIF-1), a global regulator that belongs to the basic helix-loop-helix PAS family. Although HIF-1 is a heterodimer composed of α and β subunits, its activity is primarily determined by hypoxia-induced stabilization of HIF-1α, which is otherwise rapidly degraded in oxygenated cells. We report the identification of an oxygen-dependent degradation (ODD) domain within HIF-1α that controls its degradation by the ubiquitin-proteasome pathway. The ODD domain consists of ≈200 amino acid residues, located in the central region of HIF-1α. Because portions of the domain independently confer degradation of HIF-1α, deletion of this entire region is required to give rise to a stable HIF-1α, capable of heterodimerization, DNA-binding, and transactivation in the absence of hypoxic signaling. Conversely, the ODD domain alone confers oxygen-dependent instability when fused to a stable protein, Gal4. Hence, the ODD domain plays a pivotal role for regulating HIF-1 activity and thereby may provide a means of controlling gene expression by changes in oxygen tension.
2,113 citations
TL;DR: Findings strongly suggest that the hypoxia induced changes in HIF-1alpha stability and subsequent gene activation are mediated by redox-induced changes.
1,600 citations
TL;DR: EPAS1 expression is limited to the endothelium of mouse embryos and is capable of specifically activating the transcription of the endothelial tyrosine kinase gene Tie-2, raising the possibility that EPAS1 may represent an important regulator of vascularization, perhaps involving the regulation of endothelial cell gene expression in response to hypoxia.
Abstract: Here we describe the cloning and characterization of a PAS domain transcription factor termed endothelial PAS-1 (EPAS1). This protein shares 48% sequence identity with hypoxia inducible factor (HIF-1alpha) and lesser similarity with other members of the basic helix-loop-helix/PAS domain family of transcription factors. Like HIF-1alpha, EPAS1 binds to and activates transcription from a DNA element originally isolated from the erythropoietin gene and containing the sequence 5'-GCCCTACGTGCTGTCTCA-3'. Activation by both HIF-1alpha and EPAS1 is stimulated by hypoxic conditions. EPAS1 forms a heterodimeric complex with the aryl hydrocarbon nuclear transporter prior to transcriptional activation of target genes. EPAS1 expression is limited to the endothelium of mouse embryos and, in agreement with its cell type-specific expression pattern, is capable of specifically activating the transcription of the endothelial tyrosine kinase gene Tie-2. These observations raise the possibility that EPAS1 may represent an important regulator of vascularization, perhaps involving the regulation of endothelial cell gene expression in response to hypoxia.
1,325 citations