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Proc Natl Acad Sci U S A. 2012 Oct 16;109(42):17123-8. doi: 10.1073/pnas.1205156109. Epub 2012 Oct 1.

Transcriptional repressor PRR5 directly regulates clock-output pathways.

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  • 1Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan. norih1@agr.nagoya-u.ac.jp

Abstract

The circadian clock is an endogenous time-keeping mechanism that enables organisms to adapt to external daily cycles. The clock coordinates biological activities with these cycles, mainly through genome-wide gene expression. However, the exact mechanism underlying regulation of circadian gene expression is poorly understood. Here we demonstrated that an Arabidopsis PSEUDO-RESPONSE REGULATOR 5 (PRR5), which acts in the clock genetic circuit, directly regulates expression timing of key transcription factors involved in clock-output pathways. A transient expression assay and ChIP-quantitative PCR assay using mutated PRR5 indicated that PRR5 associates with target DNA through binding at the CCT motif in vivo. ChIP followed by deep sequencing coupled with genome-wide expression profiling revealed the direct-target genes of PRR5. PRR5 direct-targets include genes encoding transcription factors involved in flowering-time regulation, hypocotyl elongation, and cold-stress responses. PRR5-target gene expression followed a circadian rhythm pattern with low, basal expression from noon until midnight, when PRR9, PRR7, and PRR5 were expressed. ChIP-quantitative PCR assays indicated that PRR7 and PRR9 bind to the direct-targets of PRR5. Genome-wide expression profiling using a prr9 prr7 prr5 triple mutant suggests that PRR5, PRR7, and PRR9 repress these targets. Taken together, our results illustrate a genetic network in which PRR5, PRR7, and PRR9 directly regulate expression timing of key transcription factors to coordinate physiological processes with daily cycles.

PMID:
23027938
[PubMed - indexed for MEDLINE]
PMCID:
PMC3479524
Free PMC Article

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