Physical interactions among circadian clock proteins KaiA, KaiB and KaiC in cyanobacteria

Iwasaki, Hideo

doi:10.1093/emboj/18.5.1137

Cited by 167 publications

(165 citation statements)

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“…Examples include the interaction of PER and TIM in Drosophila as a means of controlling the nuclear entry and degradation of both proteins (Edery, 1999;Meyer et al, 2006), the interactions among Kai proteins in cyanobacteria (Iwasaki et al, 1999) and heterodimers of the transcription factors mCLOCK and BMAL1, and interactions among three mPER (PER1-PER3) and two CRYPTOCHROME (mCRY1 and mCRY2) proteins in mammals (Reppert and Weaver, 2002;Lowrey and Takahashi, 2004). In this study, we demonstrate that CCA1 and LHY have similar expression patterns, bind to a similar region of the Lhcb1*3 promoter, colocalize in the nucleus, and that they can physically interact both in vitro and in plants.…”

Section: Discussionmentioning

confidence: 99%

CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL Function Synergistically in the Circadian Clock of Arabidopsis

Knowles

Andronis³

et al. 2009

Plant Physiology

186

145

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The circadian clock is an endogenous mechanism that coordinates biological processes with daily and seasonal changes in the environment. Heterodimerization of central clock components is an important way of controlling clock function in several different circadian systems. CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) are Myb-related proteins that function in or close to the central oscillator in Arabidopsis (Arabidopsis thaliana). Single mutants of cca1 and lhy have a phenotype of short-period rhythms. cca1 lhy double mutants show an even shorter period phenotype than the cca1 single mutant, suggesting that CCA1 and LHY are only partially functionally redundant. To determine whether CCA1 and LHY act in parallel or synergistically in the circadian clock, we examined their expression in both light-grown and etiolated seedlings. We have shown that LHY and CCA1 bind to the same region of the promoter of a Light-harvesting chlorophyll a/b protein (Lhcb, also known as CAB). CCA1 and LHY can form homodimers, and they also colocalize in the nucleus and heterodimerize in vitro and in vivo. In Arabidopsis, CCA1 and LHY physically interact in a manner independent of photoperiod. Moreover, results from gel filtration chromatography indicate that CCA1 and LHY are present in the same large complex in plants. Taken together, these results imply that CCA1 and LHY function synergistically in regulating circadian rhythms of Arabidopsis.

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Section: Discussionmentioning

confidence: 99%

CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL Function Synergistically in the Circadian Clock of Arabidopsis

Knowles

Andronis³

et al. 2009

Plant Physiology

186

145

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“…KaiC consists of two structurally related ATP-binding domains (Iwasaki et al 1999), and it belongs to the superfamily of bacterial DNA helicases/recombinases (Leipe et al 2000). Like other members of this family, KaiC forms an ATP-dependent homo-hexameric complex (Mori et al 2002).…”

Section: The Circadian Clock Of Cyanobacteriamentioning

confidence: 99%

Transcriptional and post-transcriptional regulation of the circadian clock of cyanobacteria and Neurospora

Brunner¹,

Schafmeier²

2006

Genes Dev.

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Circadian clocks are self-sustained oscillators modulating rhythmic transcription of large numbers of genes. Clock-controlled gene expression manifests in circadian rhythmicity of many physiological and behavioral functions. In eukaryotes, expression of core clock components is organized in a network of interconnected positive and negative feedback loops. This network is thought to constitute the pacemaker that generates circadian rhythmicity. The network of interconnected loops is embedded in a supra-net via a large number of interacting factors that affect expression and function of core clock components on transcriptional and post-transcriptional levels. In particular, phosphorylation and dephosphorylation of clock components are critical processes ensuring robust self-sustained circadian rhythmicity and entrainment of clocks to external cues. In cyanobacteria, three clock proteins have the capacity to generate a self-sustained circadian rhythm of autophosphorylation and dephosphorylation independent of transcription and translation. This phosphorylation rhythm regulates the function of these clock components, which then facilitate rhythmic gene transcription, including negative feedback on their own genes. In this article, we briefly present the mechanism of clock function in cyanobacteria. We then discuss in detail the contribution of transcriptional feedback and protein phosphorylation to various functional aspects of the circadian clock of Neurospora crassa.Circadian rhythms are found in numerous light-perceiving organisms including cyanobacteria, algae, fungi, plants, insects, and vertebrates. The rhythms are supported by cell-autonomous circadian clocks, which regulate expression of a large number of genes on the level of transcription (for review, see Transcriptional/translational feedback loops are hallmarks of circadian clocks in all organisms. In eukaryotes, expression of core clock components is organized in a complex network of interconnected positive and negative feedback loops (for review, see Dunlap and Loros 2004;Gachon et al. 2004;Hardin 2005). This network of gene expression is assumed to generate circadian rhythmicity. Elimination of key components of these interconnected loops disrupts many, if not all, rhythmic outputs, depending on the organism. Expression, subcellular localization, assembly, function, and turnover of clock components are crucial for circadian rhythmicity, and thus, the core clock is embedded in a supra-net of cellular machinery regulating various aspects of clock function. Protein phosphorylation and dephosphorylation are important regulatory mechanisms that are critical for self-sustained circadian rhythmicity and entrainment of clocks to external cues. It is unclear to what extent reversible phosphorylations are mechanistically instrumental for generation of rhythmicity in eukaryotic clocks.Recent findings have shown that clock proteins in cyanobacteria generate a self-sustained circadian rhythm of autophosphorylation and dephosphorylation, which is independent of tra...

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“…This profound control of transcriptional activity in the cyanobacterium Synechococcus elongatus PCC 7942 is regulated by a molecular clockwork that is encoded by 3 genes-kaiA, kaiB, and kaiC-that form a cluster on the chromosome; inactivation of any of the kai genes abolishes clock function (Ishiura et al, 1998). 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).…”

Section: The Circadian Clock System In Cyanobacteriamentioning

confidence: 99%

“…Neither kaiA nor kaiB show obvious similarities to any other known genes; however, kaiC appears to be an internally duplicated version of a bacterial recA/dnaB-like gene (Iwasaki et al, 1999;Leipe et al, 2000). In bacteria, RecA functions as a DNA recombinase, and DnaB is a DNA helicase; thus, the similarity implies that KaiC might also interact directly with DNA.…”

Section: The Circadian Clock System In Cyanobacteriamentioning

confidence: 99%

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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Physical interactions among circadian clock proteins KaiA, KaiB and KaiC in cyanobacteria

Cited by 167 publications

References 38 publications

CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL Function Synergistically in the Circadian Clock of Arabidopsis

CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL Function Synergistically in the Circadian Clock of Arabidopsis

Transcriptional and post-transcriptional regulation of the circadian clock of cyanobacteria and Neurospora

No Promoter Left Behind: Global Circadian Gene Expression in Cyanobacteria

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