No Transcription-Translation Feedback in Circadian Rhythm of KaiC Phosphorylation

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.

[1]  S. Golden,et al.  Structure and function from the circadian clock protein KaiA of Synechococcus elongatus: A potential clock input mechanism , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[2]  Takao Kondo,et al.  Circadian Formation of Clock Protein Complexes by KaiA, KaiB, KaiC, and SasA in Cyanobacteria* , 2003, The Journal of Biological Chemistry.

[3]  T. Kondo,et al.  Circadian Rhythms in the Synthesis and Degradation of a Master Clock Protein KaiC in Cyanobacteria* , 2004, Journal of Biological Chemistry.

[4]  Tetsuya Mori,et al.  Circadian clock‐protein expression in cyanobacteria: rhythms and phase setting , 2000, The EMBO journal.

[5]  Takao Kondo,et al.  KaiB functions as an attenuator of KaiC phosphorylation in the cyanobacterial circadian clock system , 2003, The EMBO journal.

[6]  C. Johnson,et al.  Expression of a gene cluster kaiABC as a circadian feedback process in cyanobacteria. , 1998, Science.

[7]  S. Golden,et al.  A KaiC-Interacting Sensory Histidine Kinase, SasA, Necessary to Sustain Robust Circadian Oscillation in Cyanobacteria , 2000, Cell.

[8]  Martin Egli,et al.  Identification of key phosphorylation sites in the circadian clock protein KaiC by crystallographic and mutagenetic analyses. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[9]  W. Doolittle,et al.  The cyanobacterial genome, its expression, and the control of that expression. , 1979, Advances in microbial physiology.

[10]  Tetsuya Mori,et al.  Cyanobacterial circadian clockwork: roles of KaiA, KaiB and the kaiBC promoter in regulating KaiC , 2003, The EMBO journal.

[11]  S. Kay,et al.  Time zones: a comparative genetics of circadian clocks , 2001, Nature Reviews Genetics.

[12]  S. Golden,et al.  CikA, a bacteriophytochrome that resets the cyanobacterial circadian clock. , 2000, Science.

[13]  C. Johnson,et al.  Circadian programming in cyanobacteria. , 2001, Seminars in cell & developmental biology.

[14]  Takao Kondo,et al.  KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[15]  Atsushi Hijikata,et al.  Role of KaiC phosphorylation in the circadian clock system of Synechococcus elongatus PCC 7942. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[16]  Takao Kondo,et al.  Global gene repression by KaiC as a master process of prokaryotic circadian system. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[17]  T. Kondo,et al.  Nucleotide binding and autophosphorylation of the clock protein KaiC as a circadian timing process of cyanobacteria. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[18]  D. Vazquez,et al.  The effects of the rifamycin antibiotics on algae , 1970, FEBS letters.

[19]  A. Sehgal,et al.  Role of Molecular Oscillations in Generating Behavioral Rhythms in Drosophila , 2001, Neuron.

[20]  S. Golden,et al.  Circadian orchestration of gene expression in cyanobacteria. , 1995, Genes & development.