Document Detail


Circadian output, input, and intracellular oscillators: insights into the circadian systems of single cells.
MedLine Citation:
PMID:  18419278     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Circadian output comprises the business end of circadian systems in terms of adaptive significance. Work on Neurospora pioneered the molecular analysis of circadian output mechanisms, and insights from this model system continue to illuminate the pathways through which clocks control metabolism and overt rhythms. In Neurospora, virtually every strain examined in the context of rhythms bears the band allele that helps to clarify the overt rhythm in asexual development. Recent cloning of band showed it to be an allele of ras-1 and to affect a wide variety of signaling pathways yielding enhanced light responses and asexual development. These can be largely phenocopied by treatments that increase levels of intracellular reactive oxygen species. Although output is often unidirectional, analysis of the prd-4 gene provided an alternative paradigm in which output feeds back to affect input. prd-4 is an allele of checkpoint kinase-2 that bypasses the requirement for DNA damage to activate this kinase; FRQ is normally a substrate of activated Chk2, so in Chk2(PRD-4), FRQ is precociously phosphorylated and the clock cycles more quickly. Finally, recent adaptation of luciferase to fully function in Neurospora now allows the core FRQ/WCC feedback loop to be followed in real time under conditions where it no longer controls the overt rhythm in development. This ability can be used to describe the hierarchical relationships among FRQ-Less Oscillators (FLOs) and to see which are connected to the circadian system. The nitrate reductase oscillator appears to be connected, but the oscillator controlling the long-period rhythm elicited upon choline starvation appears completely disconnected from the circadian system; it can be seen to run with a very long noncompensated 60-120-hour period length under conditions where the circadian FRQ/WCC oscillator continues to cycle with a fully compensated circadian 22-hour period.
Authors:
J J Loros; J C Dunlap; L F Larrondo; M Shi; W J Belden; V D Gooch; C-H Chen; C L Baker; A Mehra; H V Colot; C Schwerdtfeger; R Lambreghts; P D Collopy; J J Gamsby; C I Hong
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Cold Spring Harbor symposia on quantitative biology     Volume:  72     ISSN:  0091-7451     ISO Abbreviation:  Cold Spring Harb. Symp. Quant. Biol.     Publication Date:  2007  
Date Detail:
Created Date:  2008-04-18     Completed Date:  2008-08-01     Revised Date:  2014-09-16    
Medline Journal Info:
Nlm Unique ID:  1256107     Medline TA:  Cold Spring Harb Symp Quant Biol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  201-14     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Circadian Rhythm / genetics,  physiology*
Feedback, Physiological
Fungal Proteins / genetics,  physiology
Genes, Fungal
Models, Biological
Neurospora crassa / genetics,  growth & development,  physiology*
Periodicity
Grant Support
ID/Acronym/Agency:
GM068087/GM/NIGMS NIH HHS; GM083336/GM/NIGMS NIH HHS; GM34985/GM/NIGMS NIH HHS; P01 GM068087/GM/NIGMS NIH HHS; P01 GM068087-07/GM/NIGMS NIH HHS; R01 GM034985/GM/NIGMS NIH HHS; R01 GM034985-23/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
0/FRQ protein, Neurospora crassa; 0/Fungal Proteins
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