Crystal Structure of the Heterodimeric CLOCK:BMAL1 Transcriptional Activator Complex

Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Science (Impact Factor: 33.61). 05/2012; 337(6091):189-94. DOI: 10.1126/science.1222804
Source: PubMed


The circadian clock in mammals is driven by an autoregulatory transcriptional feedback mechanism that takes approximately
24 hours to complete. A key component of this mechanism is a heterodimeric transcriptional activator consisting of two basic
helix-loop-helix PER-ARNT-SIM (bHLH-PAS) domain protein subunits, CLOCK and BMAL1. Here, we report the crystal structure of
a complex containing the mouse CLOCK:BMAL1 bHLH-PAS domains at 2.3 Å resolution. The structure reveals an unusual asymmetric
heterodimer with the three domains in each of the two subunits—bHLH, PAS-A, and PAS-B—tightly intertwined and involved in
dimerization interactions, resulting in three distinct protein interfaces. Mutations that perturb the observed heterodimer
interfaces affect the stability and activity of the CLOCK:BMAL1 complex as well as the periodicity of the circadian oscillator.
The structure of the CLOCK:BMAL1 complex is a starting point for understanding at an atomic level the mechanism driving the
mammalian circadian clock.

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    • "In mammalian CRYs, the tail and a preceding predicted coiledcoil helix of the PHR mediate interactions with C-terminal mBMAL1 residues (Czarna et al., 2011; Kiyohara et al., 2006; Sato et al., 2006) and thereby repression of mCLOCK/ mBMAL1-activated transcription (Chaves et al., 2006). The PHR interacts with C-terminal regions of mPER1 and mPER2 (Miyazaki et al., 2001; Yagita et al., 2002), with the PAS (PER- ARNT-SIM) domains of mCLOCK (Huang et al., 2012) and with FBXL3 (Lamia et al., 2009). "
    Dataset: mmc2

    Full-text · Dataset · Sep 2015
    • "Arrowheads indicate point mutations in the PAS-A domain. (C) Mutation of the PASD1 PAS-A b sheet interface (V36E/M45R) does not affect repression of CLOCK:BMAL1, while mutation of analogous residues in the PAS-A domain of CLOCK (L113E/ F122R) reduces activation of the Per1:luc gene (Huang et al., 2012) (n = 3 experiments, mean ± SD). Significance was determined by Student's t test: **p < 0.01. "
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    ABSTRACT: The circadian clock orchestrates global changes in transcriptional regulation on a daily basis via the bHLH-PAS transcription factor CLOCK:BMAL1. Pathways driven by other bHLH-PAS transcription factors have a homologous repressor that modulates activity on a tissue-specific basis, but none have been identified for CLOCK:BMAL1. We show here that the cancer/testis antigen PASD1 fulfills this role to suppress circadian rhythms. PASD1 is evolutionarily related to CLOCK and interacts with the CLOCK:BMAL1 complex to repress transcriptional activation. Expression of PASD1 is restricted to germline tissues in healthy individuals but can be induced in cells of somatic origin upon oncogenic transformation. Reducing PASD1 in human cancer cells significantly increases the amplitude of transcriptional oscillations to generate more robust circadian rhythms. Our results describe a function for a germline-specific protein in regulation of the circadian clock and provide a molecular link from oncogenic transformation to suppression of circadian rhythms. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · Apr 2015 · Molecular cell
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    • "These proteins regulate the timing for adults to hatch from pupae (opposite to diapause) and the temperature preference rhythm in Drosophila (Blanchardon et al., 2001; Kaneko et al., 2012). Mapping amino acid differences between species to 3D structure templates shows that these mutations concentrate on one side of the CLOCK/CYCLE complex (Huang et al., 2012), forming clusters on the surface (Figure 4C). A similar distribution of mutation sites is observed in PERIOD (Figure S5E). "
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    ABSTRACT: Predicting phenotype from genotype represents the epitome of biological questions. Comparative genomics of appropriate model organisms holds the promise of making it possible. However, the high heterozygosity of many Eukaryotes currently prohibits assembling their genomes. Here, we report the 376 Mb genome sequence of Papilio glaucus (Pgl), the first sequenced genome from the Papilionidae family. We obtained the genome from a wild-caught specimen using a cost-effective strategy that overcomes the high (2%) heterozygosity problem. Comparative analyses suggest the molecular bases of various phenotypic traits, including terpene production in the Papilionidae-specific organ, osmeterium. Comparison of Pgl and Papilio canadensis transcriptomes reveals mutation hotspots (4% genes) associated with their divergence: four key circadian clock proteins are enriched in inter-species mutations and likely responsible for the difference in pupal diapause. Finally, the Pgl genome confirms Papilio appalachiensis as a hybrid of Pgl and Pca, but suggests it inherited 3/4 of its genes from Pca. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Feb 2015 · Cell Reports
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