KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria

Iwasaki, Hideo; Nishiwaki, Taeko; Kitayama, Yohko; Nakajima, Masato; Kondo, Takao

doi:10.1073/pnas.222467299

Cited by 279 publications

(396 citation statements)

References 17 publications

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“…Furthermore, our previous results from a radioactive phosphate uptake assay showed that a small amount of phosphate was incorporated into KaiC even when KaiA was not included in the reaction (Iwasaki et al 2002;Kitayama et al 2003). We also confirmed that the ratio of phosphorylated serine and threonine was not altered by the presence of KaiA, whereas KaiA increased the overall level of phosphorylation at both residues (Iwasaki et al 2002).…”

Section: A Sequential Program Of Kaic Phosphorylationsupporting

confidence: 84%

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A Cyanobacterial Circadian Clock Based on the Kai Oscillator

Kondo¹

2007

Cold Spring Harbor Symposia on Quantitative Biology

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Section: A Sequential Program Of Kaic Phosphorylationsupporting

confidence: 84%

“…Therefore, KaiC is the primary determinant of the circadian period of cyanobacteria. One candidate for the molecular process that determines the circadian period is the phosphorylation of KaiC, which exhibits a robust circadian rhythm in its phosphorylation level in vivo (Iwasaki et al 2002).…”

Section: Introductionmentioning

confidence: 99%

A Cyanobacterial Circadian Clock Based on the Kai Oscillator

Kondo¹

2007

Cold Spring Harbor Symposia on Quantitative Biology

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“…In one of the more remarkable discoveries in the field in recent years, it was shown that a circadian oscillation of KaiC phosphorylation could be reconstituted in vitro with the purified KaiA, KaiB, and KaiC proteins . KaiA enhances KaiC autophosphorylation, while KaiB antagonizes the effects of KaiA (Iwasaki et al, 2002;Williams et al, 2002;Kitayama et al, 2003;Xu et al, 2003).…”

Section: The Circadian Clock System In Cyanobacteriamentioning

confidence: 99%

“…The proteins encoded by these genes interact with one another (Iwasaki et al, 1999;Taniguchi et al, 2001;Xu et al, 1999) to form large complexes in vivo with KaiC as the core (Kageyama et al, 2003). KaiC exists in both phosphorylated and nonphosphorylated forms in vivo, and its phosphorylation status is correlated with clock speed (Nishiwaki et al, 2000;Iwasaki et al, 2002;Xu et al, 2003;Johnson, 2004). In one of the more remarkable discoveries in the field in recent years, it was shown that a circadian oscillation of KaiC phosphorylation could be reconstituted in vitro with the purified KaiA, KaiB, and KaiC proteins .…”

Section: The Circadian Clock System In Cyanobacteriamentioning

confidence: 99%

“…Indeed, KaiC binds DNA substrates in vitro with low affinity (Mori et al, 2002). KaiC also interacts with a 2-component histidine protein kinase, SasA (Iwasaki et al, 2002), and stimulates the autophosphorylation of SasA (Smith and Williams, in press), but SasA does not alter the phosphorylation status of KaiC. Recently, a candidate protein that may function as the cognate response regulator with SasA has been identified (Takai et al, 2006); this response regulator, called RpaA, interacts with SasA and contains a leucine zipper DNA-binding motif.…”

Section: The Circadian Clock System In Cyanobacteriamentioning

confidence: 99%

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No Promoter Left Behind: Global Circadian Gene Expression in Cyanobacteria

Woelfle

Johnson

2006

J Biol Rhythms

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Prokaryotic cyanobacteria express robust circadian (daily) rhythms under the control of a clock system that appears to be similar to those of eukaryotes in many ways. On the other hand, the KaiABC-based core cyanobacterial clockwork is clearly different from the transcriptiontranslation feedback loop model of eukaryotic clocks in that the cyanobacterial clock system regulates gene expression patterns globally, and specific clock gene promoters are not essential in mediating the circadian feedback loop. A novel model, the oscilloid model, proposes that the KaiABC oscillator ultimately mediates rhythmic changes in the status of the cyanobacterial chromosome, and these topological changes underlie the global rhythms of transcription. The authors suggest that this model represents one of several possible modes of regulating gene expression by circadian clocks, even those of eukaryotes. Keywords circadian; biological clock; kai; prokaryote; global gene expression; supercoiling Animals, plants, fungi, and cyanobacteria all display daily or circadian rhythms in their biochemistry, physiology, and/or behavior that are controlled by biological clocks (Dunlap et al., 2004). A variety of biological processes in various organisms are controlled by biological clocks such as gene expression, photosynthesis, sleeping/waking, and development, and this regulation is thought to help organisms adapt to the daily changes in light, temperature, and other factors in their environment. Circadian regulation of gene expression (i.e., the levels of specific proteins in cells) can be accomplished by clock control of transcription, mRNA stability, translation, and protein degradation. A particularly fascinating example of translational control by a circadian clock is that in the dinoflagellate alga, Gonyaulax (Rossini et al., 2003). However, we focus our discussion specifically on clock control of cyanobacterial gene expression at the level of transcription.In general, studies of circadian gene expression in eukaryotes have often used microarray analyses to show that a relatively small proportion of genes (~5%-15%) in eukaryotic genomes display rhythms in mRNA abundance. While microarray technology is well advanced, it should be noted that microarrays are not very sensitive to small changes of mRNA abundance, and moreover, they are not a good measure of rhythmic transcriptional activity for mRNAs that are either very unstable or very stable. Therefore, microarray results might not be reflective of transcriptional control in detail.

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Phosphorylation at Thr432 induces structural destabilization of the CII ring in the circadian oscillator KaiC

et al. 2017

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KaiC is the central oscillator protein in the cyanobacterial circadian clock. KaiC oscillates autonomously between phosphorylated and dephosphorylated states on a 24-h cycle in vitro by mixing with KaiA and KaiB in the presence of ATP. KaiC forms a C 6 -symmetrical hexamer, which is a double ring structure of homologous N-terminal and C-terminal domains termed CI and CII, respectively. Here, through the characterization of an isolated CII domain protein, CII KaiC , we show that phosphorylation of KaiC Thr432 destabilizes the hexameric state of the CII ring to a monomeric state. The results suggest that the stable hexameric CI ring acts as a molecular bundle to hold the CII ring, which undergoes dynamic structural changes upon phosphorylation.

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KaiA-stimulated KaiC phosphorylation in circadian timing loops in cyanobacteria

Cited by 279 publications

References 17 publications

A Cyanobacterial Circadian Clock Based on the Kai Oscillator

A Cyanobacterial Circadian Clock Based on the Kai Oscillator

No Promoter Left Behind: Global Circadian Gene Expression in Cyanobacteria

Phosphorylation at Thr432 induces structural destabilization of the CII ring in the circadian oscillator KaiC

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