title: Formation of a repressive complex in the mammalian circadian clock is mediated by the secondary pocket of CRY1.
abstract: The basic helix-loop-helix PAS domain (bHLH-PAS) transcription factor CLOCK:BMAL1 (brain and muscle Arnt-like protein 1) sits at the core of the mammalian circadian transcription/translation feedback loop. Precise control of CLOCK:BMAL1 activity by coactivators and repressors establishes the ∼24-h periodicity of gene expression. Formation of a repressive complex, defined by the core clock proteins cryptochrome 1 (CRY1):CLOCK:BMAL1, plays an important role controlling the switch from repression to activation each day. Here we show that CRY1 binds directly to the PAS domain core of CLOCK:BMAL1, driven primarily by interaction with the CLOCK PAS-B domain. Integrative modeling and solution X-ray scattering studies unambiguously position a key loop of the CLOCK PAS-B domain in the secondary pocket of CRY1, analogous to the antenna chromophore-binding pocket of photolyase. CRY1 docks onto the transcription factor alongside the PAS domains, extending above the DNA-binding bHLH domain. Single point mutations at the interface on either CRY1 or CLOCK disrupt formation of the ternary complex, highlighting the importance of this interface for direct regulation of CLOCK:BMAL1 activity by CRY1.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064.
authors.forename: Alicia K
authors.initials: AK
authors.lastname: Michael
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Fribourgh
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390.|Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390.
authors.forename: Yogarany
authors.initials: Y
authors.lastname: Chelliah
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064.
authors.forename: Colby R
authors.initials: CR
authors.lastname: Sandate
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Greg L
authors.initials: GL
authors.lastname: Hura
authors.affiliation: School of Computer Science and Engineering, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
authors.forename: Dina
authors.initials: D
authors.lastname: Schneidman-Duhovny
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064.
authors.forename: Sarvind M
authors.identifier: 0000-0002-6959-0577
authors.initials: SM
authors.lastname: Tripathi
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390.|Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Takahashi
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064; cpartch@ucsc.edu.|Center for Circadian Biology, University of California, San Diego, CA 92161.
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Partch
mesh_terms: D056930:ARNTL Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D056926:CLOCK Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D057906:Circadian Clocks / Q000235:genetics*; D056931:Cryptochromes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018360:Crystallography, X-Ray; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D000072417:Protein Domains; D061987:Sf9 Cells; D018411:Spodoptera
chemical_list: D056930:ARNTL Transcription Factors; C538964:Cry1 protein, mouse; D056931:Cryptochromes; D056926:CLOCK Proteins
keywords: PAS domains; circadian rhythms; cryptochrome; integrative modeling