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Proc Natl Acad Sci U S A. 2019 Jun 4;116(23):11528-11536. doi: 10.1073/pnas.1903357116. Epub 2019 May 16.

Casein kinase 1 family regulates PRR5 and TOC1 in the Arabidopsis circadian clock.

Author information

1
Department of Chemistry, Graduate School of Science, Nagoya University, 464-8602 Nagoya, Japan.
2
Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602 Nagoya, Japan.
3
Institute of Transformative Bio-Molecules, Nagoya University, 464-8601 Nagoya, Japan.
4
Japan Science and Technology Agency (JST) Precursory Research for Embryonic Science and Technology, 464-8602 Nagoya, Japan.
5
Department of Applied Biological Chemistry, Graduate School of Life and Agricultural Sciences, The University of Tokyo, 113-8657 Tokyo, Japan.
6
College of Bioscience and Biotechnology, Chubu University, 487-8501 Kasugai, Japan.
7
Department of Botany, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan.
8
Department of Applied Chemistry, Waseda University, 169-8555 Tokyo, Japan.
9
Graduate School of Bioagricultural Sciences, Nagoya University, 464-8601 Nagoya, Japan.
10
Keck School of Medicine, University of Southern California, Los Angeles, CA 90033.
11
JST Exploratory Research for Advanced Technology, Itami Molecular Nanocarbon Project, Nagoya University, 464-8602 Nagoya, Japan.
12
Department of Applied Chemistry, Waseda University, 169-8555 Tokyo, Japan; junyamaguchi@waseda.jp nnakamichi@itbm.nagoya-u.ac.jp.
13
Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602 Nagoya, Japan; junyamaguchi@waseda.jp nnakamichi@itbm.nagoya-u.ac.jp.

Abstract

The circadian clock provides organisms with the ability to adapt to daily and seasonal cycles. Eukaryotic clocks mostly rely on lineage-specific transcriptional-translational feedback loops (TTFLs). Posttranslational modifications are also crucial for clock functions in fungi and animals, but the posttranslational modifications that affect the plant clock are less understood. Here, using chemical biology strategies, we show that the Arabidopsis CASEIN KINASE 1 LIKE (CKL) family is involved in posttranslational modification in the plant clock. Chemical screening demonstrated that an animal CDC7/CDK9 inhibitor, PHA767491, lengthens the Arabidopsis circadian period. Affinity proteomics using a chemical probe revealed that PHA767491 binds to and inhibits multiple CKL proteins, rather than CDC7/CDK9 homologs. Simultaneous knockdown of Arabidopsis CKL-encoding genes lengthened the circadian period. CKL4 phosphorylated transcriptional repressors PSEUDO-RESPONSE REGULATOR 5 (PRR5) and TIMING OF CAB EXPRESSION 1 (TOC1) in the TTFL. PHA767491 treatment resulted in accumulation of PRR5 and TOC1, accompanied by decreasing expression of PRR5- and TOC1-target genes. A prr5 toc1 double mutant was hyposensitive to PHA767491-induced period lengthening. Together, our results reveal posttranslational modification of transcriptional repressors in plant clock TTFL by CK1 family proteins, which also modulate nonplant circadian clocks.

KEYWORDS:

Arabidopsis; circadian clock; posttranslational regulation; small molecule

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