RpaB, Another Response Regulator Operating Circadian Clock-dependent Transcriptional Regulation in Synechococcus elongatus PCC 7942

Hanaoka, Mitsumasa; Takai, Naoki; Hosokawa, Norimune; Fujiwara, Masayuki; Akimoto, Yutaro; Kobori, Nami; Iwasaki, Hideo; Kondo, Takao; Tanaka, Kan

doi:10.1074/jbc.m111.338251

Cited by 52 publications

(65 citation statements)

References 31 publications

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“…In particular, RpaB was shown to bind to the class 1 kaiBC promoter in a circadian fashion (10), presumably at the HLR1 element that overlaps with the recently described RpaAbinding site (18) (Fig. S1A).…”

Section: Resultsmentioning

confidence: 78%

“…However, the phase relationship of RpaB∼P peaks to LD cues appears to be altered in rpaA mutants. Although the absolute levels of RpaB and RpaA are constant in WT S. elongatus (10)(11)(12)20), RpaB levels dropped dramatically in LD in the absence of a functional SasA-RpaA pathway, suggesting that the clock output pathway is required to maintain the physiological levels of RpaB in LD cycles. (one-way ANOVA).…”

Section: Rpab Phosphorylation Oscillates In Ld Cycles In a Clock-indementioning

confidence: 98%

“…These and other findings (6) argue against RpaB acting by a simplistic on/off model in which the protein binds to target promoters only when it is phosphorylated, as proposed for OmpR/PhoB-like response regulators that respond to discrete signals. Recently, RpaB has also been implicated in the control of cell dimensions, for which nonphosphorylated RpaB appears to be the main player (13), and in the transcriptional oscillation of clock-regulated genes (10).…”

mentioning

confidence: 99%

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Cross-talk and regulatory interactions between the essential response regulator RpaB and cyanobacterial circadian clock output

Espinosa

Boyd

Cantos

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The response regulator RpaB (regulator of phycobilisome associated B), part of an essential two-component system conserved in cyanobacteria that responds to multiple environmental signals, has recently been implicated in the control of cell dimensions and of circadian rhythms of gene expression in the model cyanobacterium Synechococcus elongatus PCC 7942. However, little is known of the molecular mechanisms that underlie RpaB functions. In this study we show that the regulation of phenotypes by RpaB is intimately connected with the activity of RpaA (regulator of phycobilisome associated A), the master regulator of circadian transcription patterns. RpaB affects RpaA activity both through control of gene expression, a function requiring an intact effector domain, and via altering RpaA phosphorylation, a function mediated through the N-terminal receiver domain of RpaB. Thus, both phosphorylation cross-talk and coregulation of target genes play a role in the genetic interactions between the RpaA and RpaB pathways. In addition, RpaB∼P levels appear critical for survival under light:dark cycles, conditions in which RpaB phosphorylation is environmentally driven independent of the circadian clock. We propose that the complex regulatory interactions between the essential and environmentally sensitive NblS-RpaB system and the SasA-RpaA clock output system integrate relevant extra-and intracellular signals to the circadian clock.signaling network | transcription regulation | chronobiology

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Section: Resultsmentioning

confidence: 78%

Section: Rpab Phosphorylation Oscillates In Ld Cycles In a Clock-indementioning

confidence: 98%

mentioning

confidence: 99%

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Cross-talk and regulatory interactions between the essential response regulator RpaB and cyanobacterial circadian clock output

Espinosa

Boyd

Cantos

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The lack of bioluminescence reporter rhythms in an rpaA null background suggests a decoupling or insensitivity to the KaiC oscillations. RpaA activity is critical for sustaining the transcription/translation feedback loop of KaiBC expression (20); however, a recent study suggested that the response regulator RpaB, not RpaA, binds directly to the promoters of rhythmically regulated target genes, including kaiBC, and represses them (22 12 LD cycle and sampled every 3 h over 18 h. Samples were either maintained in LL or collected after entering dark at 11 h after onset of light. The overall RpaA phosphorylation level in LD is significantly lower after 1 h in dark compared with the 12-h LL sample, but the overall phosphorylation cycle remains substantially the same under both LL and LD conditions.…”

Section: Discussionmentioning

confidence: 99%

An allele of the crm gene blocks cyanobacterial circadian rhythms

Boyd

Bordowitz

Bree

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The SasA-RpaA two-component system constitutes a key output pathway of the cyanobacterial Kai circadian oscillator. To date, rhythm of phycobilisome associated (rpaA) is the only gene other than kaiA, kaiB, and kaiC, which encode the oscillator itself, whose mutation causes completely arrhythmic gene expression. Here we report a unique transposon insertion allele in a small ORF located immediately upstream of rpaA in Synechococcus elongatus PCC 7942 termed crm (for circadian rhythmicity modulator), which results in arrhythmic promoter activity but does not affect steady-state levels of RpaA. The crm ORF complements the defect when expressed in trans, but only if it can be translated, suggesting that crm encodes a small protein. The crm1 insertion allele phenotypes are distinct from those of an rpaA null; crm1 mutants are able to grow in a light:dark cycle and have no detectable oscillations of KaiC phosphorylation, whereas low-amplitude KaiC phosphorylation rhythms persist in the absence of RpaA. Levels of phosphorylated RpaA in vivo measured over time are significantly altered compared with WT in the crm1 mutant as well as in the absence of KaiC. Taken together, these results are consistent with the hypothesis that the Crm polypeptide modulates a circadian-specific activity of RpaA.chronobiology | transcription regulation

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“…The six proteins shown in Figure 1 are conserved between S. and T. elongatus, and appear to comprise a core unit capable of accounting for all of the required functions of a circadian clock. Several additional genes have been identified that play roles in the circadian rhythms of cyanobacteria (16)(17)(18)(19)(20)(21), however this review will focus on the six best-characterized gene products and the mechanisms through which they mediate timekeeping, entrainment and output signaling functions in cyanobacterial circadian rhythms. For a broader review on circadian biology in cyanobacteria, see references (4,22).…”

Section: Circadian Biology In Cyanobacteriamentioning

confidence: 99%