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Chang YG, Cohen SE, Phong C, Myers WK, Kim YI, Tseng R, Lin J, Zhang L, Boyd JS, Lee Y, Kang S, Lee D, Li S, Britt RD, Rust MJ, Golden SS, LiWang A. Circadian rhythms. A protein fold switch joins the circadian oscillator to clock output in cyanobacteria. Science 2015; 349:324-8. [PMID: 26113641 PMCID: PMC4506712 DOI: 10.1126/science.1260031] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 05/08/2015] [Indexed: 12/26/2022]
Abstract
Organisms are adapted to the relentless cycles of day and night, because they evolved timekeeping systems called circadian clocks, which regulate biological activities with ~24-hour rhythms. The clock of cyanobacteria is driven by a three-protein oscillator composed of KaiA, KaiB, and KaiC, which together generate a circadian rhythm of KaiC phosphorylation. We show that KaiB flips between two distinct three-dimensional folds, and its rare transition to an active state provides a time delay that is required to match the timing of the oscillator to that of Earth's rotation. Once KaiB switches folds, it binds phosphorylated KaiC and captures KaiA, which initiates a phase transition of the circadian cycle, and it regulates components of the clock-output pathway, which provides the link that joins the timekeeping and signaling functions of the oscillator.
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Affiliation(s)
- Yong-Gang Chang
- School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Susan E Cohen
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Connie Phong
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - William K Myers
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Yong-Ick Kim
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Roger Tseng
- School of Natural Sciences, University of California, Merced, CA 95343, USA. Quantitative and Systems Biology, University of California, Merced, CA 95343, USA
| | - Jenny Lin
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Li Zhang
- School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Joseph S Boyd
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yvonne Lee
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Shannon Kang
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - David Lee
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Sheng Li
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - R David Britt
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Michael J Rust
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Susan S Golden
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA. Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Andy LiWang
- School of Natural Sciences, University of California, Merced, CA 95343, USA. Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA. Quantitative and Systems Biology, University of California, Merced, CA 95343, USA. Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA. Health Sciences Research Institute, University of California, Merced, CA 95343, USA.
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Tarrant AM, Reitzel AM. Introduction to the symposium--keeping time during evolution: conservation and innovation of the circadian clock. Integr Comp Biol 2013; 53:89-92. [PMID: 23710043 DOI: 10.1093/icb/ict062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Diurnal and seasonal cues play critical and conserved roles in behavior, physiology, and reproduction in diverse animals. The circadian clock is a transcription-translation feedback loop that represents the molecular mechanism underlying many of these periodic processes, frequently through responses to light. Although much of the core regulatory machinery is deeply conserved among diverse animal lineages, there are also many examples of innovation in the way the clock either is constructed at the molecular-level or deployed in coordinating behavior and physiology. The nine articles contained within this issue address aspects of circadian signaling in diverse taxa, utilize wide-ranging approaches, and collectively provide thought-provoking discussion of future directions in circadian research.
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Affiliation(s)
- Ann M Tarrant
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
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