Expression of a gene cluster kaiABC as a circadian feedback process in cyanobacteria.
Cyanobacteria are the simplest organisms known to have a circadian clock. A circadian clock gene cluster kaiABC was cloned from the cyanobacterium Synechococcus. Nineteen clock mutations were mapped to the three kai genes. Promoter activities upstream of the kaiA and kaiB genes showed circadian rhythms of expression, and both kaiA and kaiBC messenger RNAs displayed circadian cycling. Inactivation of any single kai gene abolished these rhythms and reduced kaiBC-promoter activity. Continuous kaiC overexpression repressed the kaiBC promoter, whereas kaiA overexpression enhanced it. Temporal kaiC overexpression reset the phase of the rhythms. Thus, a negative feedback control of kaiC expression by KaiC generates a circadian oscillation in cyanobacteria, and KaiA sustains the oscillation by enhancing kaiC expression.
Ishiura
M
M
Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan. ishiura@bio.nagoya-u.ac.jp
Kutsuna
S
S
Aoki
S
S
Iwasaki
H
H
Andersson
C R
CR
Tanabe
A
A
Golden
S S
SS
Johnson
C H
CH
Kondo
T
T
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001683:Biological Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics* / Q000502:physiology; D005246:Feedback; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017930:Genes, Reporter; D049449:Luminescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D011993:Recombinant Fusion Proteins