Structural and functional analysis of hypoxia-inducible factor 1

Abstract

Hypoxia-inducible factor 1 (HIF-1) is a basic helix-loop-helix protein that activates transcription of hypoxia-inducible genes, including those encoding: erythropoietin, vascular endothelial growth factor, heme oxygenase-1, inducible nitric oxide synthase, and the glycolytic enzymes aldolase A, enolase 1, lactate dehydrogenase A, phosphofructokinase I, and phosphoglycerate kinase 1. Hypoxia response elements from these genes consist of a HIF-1 binding site (that contains the core sequence 5'-CGTG-3') as well as additional DNA sequences that are required for function, which in some elements include a second HIF-1 binding site. HIF-1 is a heterodimer. The HIF-1 alpha subunit is unique to HIF-1, whereas HIF-1 beta (ARNT) can dimerize with other bHLH-PAS proteins. Structural analysis of HIF-1 alpha revealed that dimerization with HIF-1 beta (ARNT) requires the HLH and PAS domains, DNA binding is mediated by the basic domain, and that HIF-1 alpha contains a carboxyl-terminal transactivation domain. Co-transfection of HIF-1 alpha and HIF-1 beta (ARNT) expression vectors and a reporter gene containing a wild-type hypoxia response element resulted in increased transcription in non-hypoxic cells and a superinduction of transcription in hypoxic cells, whereas HIF-1 expression vectors had no effect on the transcription of reporter genes containing a mutation in the HIF-1 binding site. HIF-1 alpha and HIF-1 beta (ARNT) protein levels were induced by hypoxia in all primary and transformed cell lines examined. In HeLa cells, the levels of HIF-1 alpha and HIF-1 beta protein and HIF-1 DNA-binding activity increased exponentially as cellular oxygen tension decreased, with maximum values at 0.5% oxygen and half-maximal values at 1.5 to 2% oxygen. HIF-1 alpha and HIF-1 beta (ARNT) mRNAs were detected in all human, mouse, and rat organs assayed and mRNA expression was modestly induced in rodents subjected to hypoxia. HIF-1 alpha protein levels were induced in vivo when animals were subjected to anemia or hypoxia. The HIF1A gene was mapped to human chromosome 14q21-q24 and mouse chromosome 12.

Iron deficiency drives an autosomal dominant hypophosphatemic rickets (ADHR) phenotype in fibroblast growth factor-23 (Fgf23) knock-in mice

“…5A, Lower). To examine the molecular mechanisms for the elevated Fgf23 mRNA under low-iron conditions, cells were treated with L-mimosine (L-MIM; 50 μM), a specific egg-laying-defective nine (EGLN) prolyl hydroxylase inhibitor that activates the hypoxiainduced factor (HIF) transcription factors (24), key metabolic sensors that control genes in response to iron deficiency in bone and other tissues (25). Importantly, L-MIM produced a significant, time-dependent increase in Fgf23 mRNA (P < 0.01; Fig.…”

Vanadate-induced Expression of Hypoxia-inducible Factor 1α and Vascular Endothelial Growth Factor through Phosphatidylinositol 3-Kinase/Akt Pathway and Reactive Oxygen Species

“…HIF-1␣ is a unique subunit tightly regulated in response to hypoxia (2,3), whereas HIF-1␤ is identical to the aryl hydrocarbon nuclear translocator that forms heterodimers with the aryl hydrocarbon receptor in cells (2,4). HIF-1 regulates the expression of many genes including vascular endothelial growth factor (VEGF), erythropoietin, heme oxygenase 1, aldolase, enolase, and lactate dehydrogenase A (5)(6)(7)(8). The levels of HIF-1 activity in cells correlate with tumorigenicity and angiogenesis in nude mice (9,10).…”

Inhibition of Breast Cancer Angiogenesis and Metastasis ay Targeting Hypoxia-Inducible Factor-1α

“…[41]. It also supports the survival of tumor cell under hypoxic conditions by means of the expression of gene products that advance anaerobic ATP synthesis, such as glucose transporters [26,43,44].…”

“…HIF-1 binds to the HRE DNA center recognition sequence (5′-RCGTG-3′), and plays a central role in tumor progression through the initiation and regulation of the transcription of a number of genes essential for tumor adaptation to hypoxia and has been implicated in major aspects of cancer biology, including immortalization, cellular dedifferentiation, genetic instability, vascularization, etc [21,[26][27][28][29][30], making it a principal target for anti-cancer therapy. It has also been described as unique in its expression and function in various cells of the tumor microenvironment-another feature that makes it an attractive target for therapy [31][32][33].…”