The basic-helix-loop-helix-PAS orphan MOP3 forms transcriptionally active complexes with circadian and hypoxia factors.

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.
Mesh Terms:
Animals, Basic Helix-Loop-Helix Transcription Factors, CLOCK Proteins, COS Cells, Circadian Rhythm, DNA, DNA-Binding Proteins, Dimerization, Helix-Loop-Helix Motifs, Hypoxia-Inducible Factor 1, Hypoxia-Inducible Factor 1, alpha Subunit, Nuclear Proteins, Protein Binding, Trans-Activators, Transcription Factors, Transfection
Proc. Natl. Acad. Sci. U.S.A.
Date: May. 12, 1998
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