title: Structural basis for PAS domain heterodimerization in the basic helix--loop--helix-PAS transcription factor hypoxia-inducible factor.
abstract: Biological responses to oxygen availability play important roles in development, physiological homeostasis, and many disease processes. In mammalian cells, this adaptation is mediated in part by a conserved pathway centered on the hypoxia-inducible factor (HIF). HIF is a heterodimeric protein complex composed of two members of the basic helix-loop-helix Per-ARNT-Sim (PAS) (ARNT, aryl hydrocarbon receptor nuclear translocator) domain family of transcriptional activators, HIFalpha and ARNT. Although this complex involves protein-protein interactions mediated by basic helix-loop-helix and PAS domains in both proteins, the role played by the PAS domains is poorly understood. To address this issue, we have studied the structure and interactions of the C-terminal PAS domain of human HIF-2alpha by NMR spectroscopy. We demonstrate that HIF-2alpha PAS-B binds the analogous ARNT domain in vitro, showing that residues involved in this interaction are located on the solvent-exposed side of the HIF-2alpha central beta-sheet. Mutating residues at this surface not only disrupts the interaction between isolated PAS domains in vitro but also interferes with the ability of full-length HIF to respond to hypoxia in living cells. Extending our findings to other PAS domains, we find that this beta-sheet interface is widely used for both intra- and intermolecular interactions, suggesting a basis of specificity and regulation of many types of PAS-containing signaling proteins.
authors.affiliation: Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: Paul J A
authors.initials: PJ
authors.lastname: Erbel
authors.forename: Paul B
authors.initials: PB
authors.lastname: Card
authors.forename: Ozgur
authors.initials: O
authors.lastname: Karakuzu
authors.forename: Richard K
authors.initials: RK
authors.lastname: Bruick
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
mesh_terms: D000595:Amino Acid Sequence; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites; D015687:Cell Hypoxia; D003001:Cloning, Molecular; D019281:Dimerization; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry*; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1; C424683:Hif3a protein, rat