title: Cross-talk between hypoxic and circadian pathways: cooperative roles for hypoxia-inducible factor 1alpha and CLOCK in transcriptional activation of the vasopressin gene.
abstract: The vasopressin gene is expressed in the suprachiasmatic nucleus where the basic helix-loop-helix (bHLH)-PAS factors CLOCK and MOP3 regulate circadian expression through interactions with E-box sequences. We have examined vasopressin gene regulation by HIF-1alpha, a bHLH-PAS factor involved in responses to hypoxia. By transfecting Neuro-2A cells with 5' flanking regions of vasopressin gene driving a luciferase reporter, we have shown that CLOCK and HIF-1alpha cooperate in the induction of expression from 1000 bp and 350 bp of the vasopressin promoter but do not activate a 120-bp promoter fragment. The region between -191 and -128 contains an E-box A that appears to be essential for HIF-1alpha/CLOCK-mediated transcriptional activity. However, gel-shift analysis shows that the cooperative effect of HIF-1alpha and CLOCK results in MOP3 binding, but does not involve heterodimerization of HIF-1alpha/CLOCK, at E-box A. These data indicate that cross-talk between mediators of hypoxic and circadian pathways can regulate target genes.
authors.affiliation: Molecular Neuroendocrinology Research Group, University Research Center for Neuroendocrinology, University of Bristol, Bristol Royal Infirmary, UK. m.ghorbel@bris.ac.uk
authors.forename: Mohamed T
authors.initials: MT
authors.lastname: Ghorbel
authors.forename: Judy M
authors.initials: JM
authors.lastname: Coulson
authors.forename: David
authors.initials: D
authors.lastname: Murphy
mesh_terms: D024506:5' Flanking Region / Q000502:physiology; D056930:ARNTL Transcription Factors; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D019281:Dimerization; D000860:Hypoxia / Q000503:physiopathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051379:Mice; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D011401:Promoter Regions, Genetic / Q000502:physiology; D017434:Protein Structure, Tertiary; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured; D014667:Vasopressins / Q000235:genetics*
chemical_list: D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015534:Trans-Activators; D014157:Transcription Factors; D014667:Vasopressins; C538961:Bmal1 protein, mouse; C538944:Clock protein, mouse