title: No transcription-translation feedback in circadian rhythm of KaiC phosphorylation.
abstract: An autoregulatory transcription-translation feedback loop is thought to be essential in generating circadian rhythms in any model organism. In the cyanobacterium Synechococcus elongatus, the essential clock protein KaiC is proposed to form this type of transcriptional negative feedback. Nevertheless, we demonstrate here temperature-compensated, robust circadian cycling of KaiC phosphorylation even without kaiBC messenger RNA accumulation under continuous dark conditions. This rhythm persisted in the presence of a transcription or translation inhibitor. Moreover, kinetic profiles in the ratio of KaiC autophosphorylation-dephosphorylation were also temperature compensated in vitro. Thus, the cyanobacterial clock can keep time independent of de novo transcription and translation processes.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Tomita
authors.forename: Masato
authors.initials: M
authors.lastname: Nakajima
authors.forename: Takao
authors.initials: T
authors.lastname: Kondo
authors.forename: Hideo
authors.initials: H
authors.lastname: Iwasaki
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins; D003624:Darkness; D025461:Feedback, Physiological; D008027:Light; D009154:Mutation; D009876:Operon; D010766:Phosphorylation; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D046940:Synechococcus / Q000235:genetics* / Q000378:metabolism*; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011994:Recombinant Proteins