Document Detail


Identification of a novel cryptochrome differentiating domain required for feedback repression in circadian clock function.
MedLine Citation:
PMID:  22692217     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Circadian clocks in mammals are based on a negative feedback loop in which transcriptional repression by the cryptochromes, CRY1 and CRY2, lies at the heart of the mechanism. Despite similarities in sequence, domain structure, and biochemical activity, they play distinct roles in clock function. However, detailed biochemical studies have not been straightforward and Cry function has not been examined in real clock cells using kinetic measurements. In this study, we demonstrate, through cell-based genetic complementation and real-time molecular recording, that Cry1 alone is able to maintain cell-autonomous circadian rhythms, whereas Cry2 cannot. Using this novel functional assay, we identify a cryptochrome differentiating α-helical domain within the photolyase homology region (PHR) of CRY1, designated as CRY1-PHR(313-426), that is required for clock function and distinguishes CRY1 from CRY2. Contrary to speculation, the divergent carboxyl-terminal tail domain (CTD) is dispensable, but serves to modulate rhythm amplitude and period length. Finally, we identify the biochemical basis of their distinct function; CRY1 is a much more potent transcriptional repressor than CRY2, and the strength of repression by various forms of CRY proteins significantly correlates with rhythm amplitude. Taken together, our results demonstrate that CRY1-PHR(313-426), not the divergent CTD, is critical for clock function. These findings provide novel insights into the evolution of the diverse functions of the photolyase/cryptochrome family of flavoproteins and offer new opportunities for mechanistic studies of CRY function.
Authors:
Sanjoy K Khan; Haiyan Xu; Maki Ukai-Tadenuma; Brittany Burton; Yongmei Wang; Hiroki R Ueda; Andrew C Liu
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-06-12
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  287     ISSN:  1083-351X     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-07-30     Completed Date:  2012-10-11     Revised Date:  2013-07-31    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  25917-26     Citation Subset:  IM    
Affiliation:
Department of Biological Sciences, University of Memphis, Memphis, Tennessee 38152-0001, USA.
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MeSH Terms
Descriptor/Qualifier:
Amino Acid Motifs
Circadian Clocks*
Cryptochromes / chemistry,  genetics,  metabolism*
Feedback, Physiological*
Fibroblasts / metabolism,  physiology
Gene Expression Regulation
HEK293 Cells
Humans
Models, Molecular
Protein Structure, Tertiary / physiology
Recombinant Fusion Proteins / chemistry,  genetics,  metabolism
Sequence Deletion
Structural Homology, Protein
Transcription, Genetic
Chemical
Reg. No./Substance:
0/CRY1 protein, human; 0/CRY2 protein, human; 0/Cryptochromes; 0/Recombinant Fusion Proteins
Comments/Corrections

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