title: Essential and expendable features of the circadian timekeeping mechanism.
abstract: Circadian clocks control behavioral, physiological and metabolic rhythms via one or more transcriptional feedback loops. In animals, two conserved feedback loops are thought to keep circadian time by mediating rhythmic transcription in opposite phases of the circadian cycle. Recent work in cyanobacteria nevertheless demonstrates that rhythmic transcription is dispensable for circadian timekeeping, raising the possibility that some features of the transcriptional feedback loops in animals are also expendable. Indeed, one of the two feedback loops is not necessary for circadian timekeeping in animals, but rhythmic transcription and post-translational modifications are both essential for keeping circadian time. These results not only confirm additional requirements within the animal circadian timekeeping mechanism, but also raise important questions about the function of conserved, yet expendable, features of the circadian timekeeping mechanism in animals.
authors.affiliation: Department of Biology, Center for Research on Biological Clocks, Texas A&M University, College Station, TX 77843-3258, USA. phardin@mail.bio.tamu.edu
authors.forename: Paul E
authors.initials: PE
authors.lastname: Hardin
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D025461:Feedback, Physiological / Q000502:physiology; D006801:Humans; D023421:Models, Animal; D009434:Neural Pathways / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C120526:Clk protein, Drosophila; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D014157:Transcription Factors; D056926:CLOCK Proteins