Suppression of hypoxia-inducible factor 1alpha (HIF-1alpha) transcriptional activity by the HIF prolyl hydroxylase EGLN1

J Biol Chem. 2005 Nov 11;280(45):38102-7. doi: 10.1074/jbc.M504342200. Epub 2005 Sep 12.

Abstract

The cellular response to hypoxia is, at least in part, mediated by the transcriptional regulation of hypoxia-responsive genes involved in balancing the intracellular ATP production and consumption. Recent evidence suggests that the transcription factor, HIF-1alpha, functions as a master regulator of oxygen homeostasis by controlling a broad range of cellular events in hypoxia. In normoxia, HIF-1alpha is targeted for destruction via prolyl hydroxylation, an oxygen-dependent modification that signals for recognition by the ubiquitin ligase complex containing the von Hippel-Lindau tumor suppressor. Three HIF prolyl hydroxylases (EGLN1, EGLN2, and EGLN3) have been identified in mammals, among which EGLN1 and EGLN3 are hypoxia-inducible at their mRNA levels in an HIF-1alpha-dependent manner. In this study, we demonstrated that apart from promoting HIF-1alpha proteolysis in normoxia, EGLN1 specifically represses HIF-1alpha transcriptional activity in hypoxia. Ectopic expression of EGLN1 inhibited HIF-1alpha transcriptional activity without altering its protein levels in a von Hippel-Lindau-deficient cell line, indicating a discrete activity of EGLN1 in transcriptional repression. Conversely, silencing of EGLN1 expression augmented HIF-1alpha transcriptional activity and its target gene expression in hypoxia. Thus, we proposed that the accumulated EGLN1 in hypoxia acts as a negative-feedback mechanism to modulate HIF-1alpha target gene expression. Our finding also provided new insight into the pharmacological manipulation of the HIF prolyl hydroxylase for ischemic diseases.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Cell Line
  • Gene Silencing*
  • Genes, Reporter / genetics
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / antagonists & inhibitors*
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Hypoxia-Inducible Factor-Proline Dioxygenases
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / metabolism*
  • Oxygen / metabolism
  • Oxygen / pharmacology
  • Procollagen-Proline Dioxygenase / genetics
  • Procollagen-Proline Dioxygenase / metabolism*
  • Protein Binding / drug effects
  • Transcription, Genetic*

Substances

  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Immediate-Early Proteins
  • EGLN1 protein, human
  • Procollagen-Proline Dioxygenase
  • Hypoxia-Inducible Factor-Proline Dioxygenases
  • Oxygen