Document Detail

Hypersensitive photic responses and intact genome-wide transcriptional control without the KaiC phosphorylation cycle in the Synechococcus circadian system.
MedLine Citation:
PMID:  24244001     Owner:  NLM     Status:  MEDLINE    
Cyanobacteria are unique organisms with remarkably stable circadian oscillations. These are controlled by a network architecture that comprises two regulatory factors: posttranslational oscillation (PTO) and a transcription/translation feedback loop (TTFL). The clock proteins KaiA, KaiB, and KaiC are essential for the circadian rhythm of the unicellular species Synechococcus elongatus PCC 7942. Temperature-compensated autonomous cycling of KaiC phosphorylation has been proposed as the primary oscillator mechanism that maintains the circadian clock, even in the dark, and it controls genome-wide gene expression rhythms under continuous-light conditions (LL). However, the kaiC(EE) mutation (where "EE" represents the amino acid changes Ser431Glu and Thr432Glu), where phosphorylation cycling does not occur in vivo, has a damped but clear kaiBC expression rhythm with a long period. This suggests that there must be coupling between the robust PTO and the "slave" unstable TTFL. Here, we found that the kaiC(EE) mutant strain in LL was hypersensitive to the dark acclimation required for phase shifting. Twenty-three percent of the genes in the kaiC(EE) mutant strain exhibited genome-wide transcriptional rhythms with a period of 48 h in LL. The circadian phase distribution was also conserved significantly in most of the wild-type and kaiC(EE) mutant strain cycling genes, which suggests that the output mechanism was not damaged severely even in the absence of KaiC phosphorylation cycles. These results strongly suggest that the KaiC phosphorylation cycle is not essential for generating the genome-wide rhythm under light conditions, whereas it is important for appropriate circadian timing in the light and dark.
Miki Umetani; Norimune Hosokawa; Yohko Kitayama; Hideo Iwasaki
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-11-15
Journal Detail:
Title:  Journal of bacteriology     Volume:  196     ISSN:  1098-5530     ISO Abbreviation:  J. Bacteriol.     Publication Date:  2014 Feb 
Date Detail:
Created Date:  2014-01-10     Completed Date:  2014-03-10     Revised Date:  2014-08-03    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  548-55     Citation Subset:  IM    
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MeSH Terms
Bacterial Proteins / genetics,  metabolism*
CLOCK Proteins / genetics,  metabolism*
Gene Expression Regulation, Bacterial / physiology,  radiation effects
Genome, Bacterial*
Phosphorylation / physiology
Synechococcus / genetics,  metabolism*,  radiation effects
Transcription, Genetic / physiology*
Reg. No./Substance:
0/Bacterial Proteins; EC Proteins

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

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