Article

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: 31.48). 05/2012; 337(6091):189-94. DOI: 10.1126/science.1222804
Source: PubMed

ABSTRACT 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.

Download full-text

Full-text

Available from: Carrie L Partch, Aug 17, 2015
0 Followers
 · 
190 Views
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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.
    Cell Reports 02/2015; 10(6):910-919. DOI:10.1016/j.celrep.2015.01.026 · 8.36 Impact Factor
  • Source
    • "The CRY tails and the most C-terminal helix (a22) of the cryptochrome photolyase homology region (PHR) (Figure 1A) are involved in transcriptional repression of CLOCK/BMAL1 (Chaves et al., 2006) and BMAL1 binding (Czarna et al., 2011). The PHR interacts with C-terminal regions of PER1 and PER2 (Eide et al., 2002; Miyazaki et al., 2001 ; Ozber et al., 2010 ; Tomita et al., 2010 ; Yagita et al., 2002 ) , with FBXL3 ( Lamia et al., 2009 ; Xing et al ., 2013 ) , FBXL21 ( Hirano et al ., 2013 ; Yoo et al ., 2013 ) and with the PAS domains of CLOCK ( Huang et al ., 2012 ) . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Period (PER) proteins are essential components of the mammalian circadian clock. They form complexes with cryptochromes (CRY), which negatively regulate CLOCK/BMAL1-dependent transactivation of clock and clock-controlled genes. To define the roles of mammalian CRY/PER complexes in the circadian clock, we have determined the crystal structure of a complex comprising the photolyase homology region of mouse CRY1 (mCRY1) and a C-terminal mouse PER2 (mPER2) fragment. mPER2 winds around the helical mCRY1 domain covering the binding sites of FBXL3 and CLOCK/BMAL1, but not the FAD binding pocket. Our structure revealed an unexpected zinc ion in one interface, which stabilizes mCRY1-mPER2 interactions in vivo. We provide evidence that mCRY1/mPER2 complex formation is modulated by an interplay of zinc binding and mCRY1 disulfide bond formation, which may be influenced by the redox state of the cell. Our studies may allow for the development of circadian and metabolic modulators.
    Cell 05/2014; 157(5):1203-15. DOI:10.1016/j.cell.2014.03.057 · 33.12 Impact Factor
  • Source
    • "At the cellular level, circadian rhythms are generated by interlocked transcriptional/translational feedback loops consisting of 'clock' genes and their protein products (reviewed in Zhang & Kay, 2010; Hastings et al., 2014; Partch et al., 2014) (Fig. 1). In mammals, the core feedback loop consists of two transcriptional activators, CLOCK and BMAL1, and two transcriptional repressors, the PERIOD (PER) and CRYPTO- CHROME (CRY) proteins (Huang et al., 2012). In the morning, CLOCK and BMAL1 activate transcription of the Per (Per1, Per2 and Per3) and Cry (Cry1 and Cry2) genes by binding to the E-box (CACGTG) domain on their gene promoters. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Circadian rhythms are generated by an endogenously organized timing system that drives daily rhythms in behavior, physiology and metabolism. In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus is the locus of a master circadian clock. The SCN is synchronized to environmental changes in the light:dark cycle by direct, monosynaptic innervation via the retino-hypothalamic tract. In turn, the SCN coordinates the rhythmic activities of innumerable subordinate clocks in virtually all bodily tissues and organs. The core molecular clockwork is composed of a transcriptional/post-translational feedback loop in which clock genes and their protein products periodically suppress their own transcription. This primary loop connects to downstream output genes by additional, interlocked transcriptional feedback loops to create tissue-specific ‘circadian transcriptomes’. Signals from peripheral tissues inform the SCN of the internal state of the organism and the brain's master clock is modified accordingly. A consequence of this hierarchical, multilevel feedback system is that there are ubiquitous effects of circadian timing on genetic and metabolic responses throughout the body. This overview examines landmark studies in the history of the study of circadian timing system, and highlights our current understanding of the operation of circadian clocks with a focus on topics of interest to the neuroscience community.
    European Journal of Neuroscience 05/2014; 39(11). DOI:10.1111/ejn.12593 · 3.67 Impact Factor
Show more