title: The basic-helix-loop-helix-PAS orphan MOP3 forms transcriptionally active complexes with circadian and hypoxia factors.
abstract: We report that MOP3 is a general dimerization partner for a subset of the basic-helix-loop-helix (bHLH)-PER-ARNT-SIM (PAS) superfamily of transcriptional regulators. We demonstrated that MOP3 interacts with MOP4, CLOCK, hypoxia-inducible factor 1alpha (HIF1alpha), and HIF2alpha. A DNA selection protocol revealed that the MOP3-MOP4 heterodimer bound a CACGTGA-containing DNA element. Transient transfection experiments demonstrated that the MOP3-MOP4 and MOP3-CLOCK complexes bound this element in COS-1 cells and drove transcription from a linked luciferase reporter gene. We also deduced the high-affinity DNA binding sites for MOP3-HIF1alpha complex (TACGTGA) and used transient transfection experiments to demonstrate that the MOP3-HIF1alpha and MOP3-HIF2alpha heterodimers bound this element, drove transcription, and responded to cellular hypoxia. Finally, we found that MOP3 mRNA expression overlaps in a number of tissues with each of its four potential partner molecules in vivo.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, IL 60611, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Hogenesch
authors.forename: Y Z
authors.initials: YZ
authors.lastname: Gu
authors.forename: S
authors.initials: S
authors.lastname: Jain
authors.forename: C A
authors.initials: CA
authors.lastname: Bradfield
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D019556:COS Cells; D002940:Circadian Rhythm; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D018257:Helix-Loop-Helix Motifs; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D014162:Transfection; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D004247:DNA; D004268:DNA-Binding Proteins; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1