Hypoxia-inducible factor 1 is a basic-helix-loop-helix-PAS heterodimer regulated by cellular O2 tension.

We show that both Hypoxia-inducible factor 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 aryl hydrocarbon receptor nuclear translocator and aryl hydrocarbon receptor proteins

G L Wang; B H Jiang; E A Rue; G L Semenza

2006

Scholarcy highlights

  • Hypoxia-inducible factor 1 is found in mammalian cells cultured under reduced 02 tension and is necessary for transcriptional activation mediated by the erythropoietin gene enhancer in hypoxic cells
  • Cis-acting DNA sequences required for transcriptional activation in response to hypoxia were identified in the EPO 3' flanking region, and a trans-acting factor that binds to the enhancer, hypoxia-inducible factor 1, fulfilled criteria for a physiological regulator of EPO transcription: inducers of EPO expression induced HIF-1 DNA-binding activity with similar kinetics, inhibitors of EPO expression blocked induction of HIF-1 activity, and mutations in the EPO 3' flanking region that eliminated HIF-1 binding eliminated enhancer function
  • Purified HIF-1 subunits were fractionated by SDS/PAGE, and the 120- and 94-kDa polypeptides were transferred to poly(vinylidene difluoride) membranes and individually digested with trypsin in situ, and peptides were fractionated by reverse-phase HPLC
  • The purified 120-kDa HIF-la polypeptide was digested with trypsin, peptides were fractionated by reverse-phase HPLC, and fractions 87 and 92 were subjected to microsequencing
  • Together with our previous studies of HIF-1, the results presented here indicate that HIF-1 is a heterodimeric bHLHPAS transcription factor consisting of a 120-kDa HIF-la subunit complexed with a 91- to 94-kDa HIF-1f3 isoform
  • The observation that the HIF-1, dioxin receptor, and Sim binding sites share the sequence 5'-CGTG-3' supports the hypothesis that aryl hydrocarbon receptor nuclear translocator is capable of combinatorial association with HIF-la, aryl hydrocarbon receptor, and Sim, since this half-site is recognized by the transcription factors with which ARNT shows greatest similarity in the bHLH domain

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