Document Detail

Attenuation of the posttranslational oscillator via transcription-translation feedback enhances circadian-phase shifts in Synechococcus.
MedLine Citation:
PMID:  23940358     Owner:  NLM     Status:  MEDLINE    
Circadian rhythms are endogenous biological timing processes that are ubiquitous in organisms ranging from cyanobacteria to humans. In the photoautotrophic unicellular cyanobacterium Synechococcus elongatus PCC 7942, under continuous light (LL) conditions, the transcription-translation feedback loop (TTFL) of KaiC generates a rhythmic change in the accumulation of KaiC relative to KaiA clock proteins (KaiC/KaiA ratio), which peak and trough at subjective dawn and dusk, respectively. However, the role of TTFL in the cyanobacterial circadian system remains unclear because it is not an essential requirement for the basic oscillation driven by the Kai-based posttranslational oscillator (PTO) and the transcriptional output mechanisms. Here, we show that TTFL is important for the circadian photic resetting property in Synechococcus. The robustness of PTO, which is exemplified by the amplitude of the KaiC phosphorylation cycle, changed depending on the KaiC/KaiA ratio, which was cyclic under LL. After cells were transferred from LL to the dark, the clock protein levels remained constant in the dark. When cells were transferred from LL to continuous dark at subjective dawn, the KaiC phosphorylation cycle was attenuated with a lower KaiC/KaiA ratio, a higher KaiC phosphorylation level, and a lower amplitude than that in cells transferred at subjective dusk. We also found that the greater the degree to which PTO was attenuated in continuous dark, the greater the phase shifts upon the subsequent light exposure. Based on these results, we propose that TTFL enhances resetting of the Kai-based PTO in Synechococcus.
Norimune Hosokawa; Hiroko Kushige; Hideo Iwasaki
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-08-12
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  110     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2013 Aug 
Date Detail:
Created Date:  2013-08-28     Completed Date:  2013-11-22     Revised Date:  2014-02-27    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  14486-91     Citation Subset:  IM    
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MeSH Terms
Bacterial Proteins / metabolism
Circadian Rhythm*
Protein Biosynthesis*
Protein Processing, Post-Translational*
Synechococcus / genetics,  metabolism,  physiology*
Transcription, Genetic*
Reg. No./Substance:
0/Bacterial Proteins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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