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Transcriptional repressor PRR5 directly regulates clock-output pathways.

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.

SUBMITTER: Nakamichi N

PROVIDER: S-EPMC3479524 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Transcriptional repressor PRR5 directly regulates clock-output pathways.

Nakamichi Norihito N Kiba Takatoshi T Kiba Takatoshi T Kamioka Mari M Suzuki Takamasa T Yamashino Takafumi T Higashiyama Tetsuya T Sakakibara Hitoshi H Mizuno Takeshi T

Proceedings of the National Academy of Sciences of the United States of America 20121001 42

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 transcripti ...[more]

PMID: 23027938

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Project description:In order to identify molecular targets of USP2-45 in the small intestine, we carried out a quantitative proteomics iTraq (Isobaric tag for relative and absolute quantitation) screen to compare proteins from WT and knockout mice. With this analysis we identified, among others, the scaffolding protein Na(+)/H(+) Exchange Regulatory cofactor NHERF4 to be up-regulated (4.81-fold) in the duodenum of Usp2-KO mice. Methods : Usp2-KO and WT littermates males were entrained to 12h L:12h D for at least two weeks in light-light housing boxes. Mice were sacrificed by cervical disolcation at ZT13 under red dim light and duodenal mucosa was dissected by scraping. The tissue samples were quickly frozen in liquid nitrogen before total protein extraction. Proteins were extracted in a lysis buffer containing 8M Urea, 20mM Tris-HCl, pH 7.5, 14 µg/ml Aprotinin, 0.7 µg /ml PepstatinA 0.7 µg /ml Leupeptin, 1 mM NaVO4, 10 mM Na-Pyrophosphate, 50 µM MG132 and 1mM PMSF. Protein concentration was measured by Bradford quantitation. Relative quantitation of proteins in 4 pools of 3 KO and 4 pools of 3 WT tissue samples was carried out by iTRAQ (Isobaric Tags for Relative and Absolute Quantitation). After reduction and alkylation of cysteines, proteins were precipitated, redissolved in 8M Urea buffer and digested with trypsin (1:50 w:w) overnight. 80ug of digested material for each sample was labeled by reaction with one vial of iTRAQ 8-plex reagent (ABSciex). Samples were pooled , desalted and fractionated by off-gel electrofocusing. The 24 fractions obtained were analysed by nanoflow liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) on a hybrid linear trap LTQ-Orbitrap Velos mass spectrometer (Thermo Fisher Scientific, Bremen, Germany) on a two-hour gradient. Full MS survey scans were performed at 60’000 resolution and the ten most intense multiply charged precursor ions detected in the full MS survey scan were selected for HCD (Higher energy Collision Dissociation) fragmentation and Orbitrap analysis (7500 resolution). Each spectrum was acquired at two relative collision energies (35% and 45%) and the spectra were summed. Data files were analysed with MaxQuant 1.3.0.5 incorporating the Andromeda search engine. Further data analysis was performed using the R statistical programming language version 2.15.2 (R core team 2012). Intensities for the reporter ions 113 to 121 were normalized using the Variance Stabilizing method (R package version 3.26.0). Proteins with non-zero intensities in all channels were evaluated for differential expression using the Local-Pooled-Error method (R package version 1.32.0) followed by correction for multiple testing according to Benjamini and Hochberg.

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Transcriptional repressor PRR5 directly regulates clock-output pathways.

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Transcriptional repressor PRR5 directly regulates clock-output pathways.

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