Roles of Brahma and Brahma/SWI2-related gene 1 in hypoxic induction of the erythropoietin gene

J Biol Chem. 2004 Nov 5;279(45):46733-41. doi: 10.1074/jbc.M409002200. Epub 2004 Sep 3.

Abstract

Upon hypoxia, the human erythropoietin (EPO) gene is transactivated by the heterodimeric hypoxia-inducible factor 1 (HIF-1). Mammalian SWI/SNF is a chromatin-remodeling complex involved in the modulation of gene expression. We demonstrate that Brahma (Brm) and Brahma/SWI2-related gene 1 (Brg-1), alternative ATPase subunits of SWI/SNF, potentiate reporter gene activation mediated by HIF-1 in an ATPase-dependent manner. Brm was more potent than Brg-1 in the reporter gene assays. Simultaneous depletion of both Brm and Brg-1 by small interfering RNAs significantly compromised the transcription of the endogenous EPO gene triggered by hypoxia. Whereas knocking down Brm alone resulted in a moderate reduction in transcription of the EPO gene, depletion of Brg-1 resulted in an augmentation of transcription of both the EPO gene and the Brm gene, indicating that Brm can compensate for loss of Brg-1. Chromatin immunoprecipitation (ChIP) and sequential ChIP (re-ChIP) analysis showed that both Brm and Brg-1 associate with the enhancer region of the EPO gene in vivo in a hypoxia-dependent fashion and that each is present in a complex with HIF-1. Brm and Brg-1 were also recruited to the promoter of the vascular endothelial growth factor (VEGF) gene in a hypoxia-dependent fashion, although hypoxic induction of VEGF transcription was not affected by depletions of either or both Brm and Brg-1. Together these studies reveal a novel role for SWI/SNF in the activation of transcription of the EPO gene, indicate an important communication and compensation between Brm and Brg-1, and suggest that the requirement for SWI/SNF during hypoxic induction is gene-specific.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3' Untranslated Regions
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • Cell Line
  • Cell Line, Tumor
  • Chromatin / metabolism
  • Cross-Linking Reagents / pharmacology
  • DNA Helicases
  • Dimerization
  • Drosophila Proteins
  • Enhancer Elements, Genetic
  • Erythropoietin / biosynthesis*
  • Erythropoietin / genetics
  • Genes, Reporter
  • Genetic Vectors
  • Histones / chemistry
  • Histones / metabolism
  • Humans
  • Hypoxia*
  • Immunoprecipitation
  • Luciferases / metabolism
  • Models, Genetic
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Oxygen / metabolism
  • Plasmids / metabolism
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Trans-Activators / metabolism
  • Trans-Activators / physiology*
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*
  • Transcription, Genetic
  • Transcriptional Activation
  • Transfection
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • 3' Untranslated Regions
  • Cell Cycle Proteins
  • Chromatin
  • Cross-Linking Reagents
  • Drosophila Proteins
  • Histones
  • Nuclear Proteins
  • RNA, Small Interfering
  • Trans-Activators
  • Transcription Factors
  • Vascular Endothelial Growth Factor A
  • brm protein, Drosophila
  • Erythropoietin
  • Luciferases
  • SMARCA4 protein, human
  • DNA Helicases
  • Oxygen