A Role for Casein Kinase 2 in the Mechanism Underlying Circadian Temperature Compensation

Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.
Cell (Impact Factor: 32.24). 06/2009; 137(4):749-60. DOI: 10.1016/j.cell.2009.03.019
Source: PubMed


Temperature compensation of circadian clocks is an unsolved problem with relevance to the general phenomenon of biological compensation. We identify casein kinase 2 (CK2) as a key regulator of temperature compensation of the Neurospora clock by determining that two long-standing clock mutants, chrono and period-3, displaying distinctive alterations in compensation encode the beta1 and alpha subunits of CK2, respectively. Reducing the dose of these subunits, particularly beta1, significantly alters temperature compensation without altering the enzyme's Q(10). By contrast, other kinases and phosphatases implicated in clock function do not play appreciable roles in temperature compensation. CK2 exerts its effects on the clock by directly phosphorylating FREQUENCY (FRQ), and this phosphorylation is compromised in CK2 hypomorphs. Finally, mutation of certain putative CK2 phosphosites on FRQ, shown to be phosphorylated in vivo, predictably alters temperature compensation profiles effectively phenocopying CK2 mutants.

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Available from: Mi Shi, Mar 14, 2014
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    • "In rice, phosphorylation of circadian clock components such as OsLHY has been described, and further analysis suggests that CK2 affects the circadian clock and the flowering time through independent pathways, implying a diversification of these mechanisms during evolution of higher plants (Ogiso et al., 2010). Relevant studies in Neurospora described a role for CK2 in the regulatory mechanism of circadian clock known as temperature compensation that allows maintaining the clock as robust and accurate over a broad range of physiological temperatures (Mehra et al., 2009). Recently in Arabidopsis, it has been shown that CK2 and CCA1 activities display inverse temperature sensitivity. "

    Full-text · Dataset · Jan 2016
    • "CK2 is a holoenzyme, consisting of a tetramer of two regulatory beta subunits and two catalytic alpha subunits, which regulates a variety of cellular processes [4] including the rhythmic processes of the circadian clock and the cell cycle [5]; it is therefore a key target in anti-cancer pharmacology [6]. CK2 homologs are present in all eukaryotic life and so far, CK2 has been shown to affect circadian clock period length in mammals [5], flies [7] [8], fungi [9] [10], and plants [11] [12] [13] [14]. If the role of CK2 in the circadian clock is conserved across these species, a plausible explanation would be that unidentified, conserved targets exist. "
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    ABSTRACT: Casein Kinase 2 (CK2) is a protein kinase that phosphorylates a plethora of cellular target proteins involved in processes including DNA repair, cell cycle control, and circadian timekeeping. CK2 is functionally conserved across eukaryotes, although the substrate proteins identified in a range of complex tissues are often different. The marine alga Ostreococcus tauri is a unicellular eukaryotic model organism ideally suited to efficiently study generic roles of CK2 in the cellular circadian clock. Overexpression of CK2 leads to a slow circadian rhythm, verifying functional conservation of CK2 in timekeeping. The proteome was analysed in wild-type and CK2-overexpressing algae at dawn and dusk, revealing that differential abundance of the global proteome across the day is largely unaffected by overexpression. However, CK2 activity contributed more strongly to timekeeping at dusk than at dawn. The phosphoproteome of a CK2 overexpression line and cells treated with CK2 inhibitor was therefore analysed and compared to control cells at dusk. We report an extensive catalogue of 447 unique CK2-responsive differential phosphopeptide motifs to inform future studies into CK2 activity in the circadian clock of more complex tissues This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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    • "In A. thaliana, CK2 phosphorylates Circadian Clock-Associated 1(CCA1) and Late Elongated Hypocotyl (LHY) and over-expression of the CK2 regulatory subunit CKB3 shortens the period of these clock genes, accelerating plant flowering time [115, 116]. CK2 is involved in temperature compensation of the clock in fungi and plants, which allows for robust timekeeping [117, 118]. Within O. tauri we have identified CK2 motifs in CCA1 which are conserved (Figure 9, Additional file 4: Figure S3E) with the observed A. thaliana sites [115, 116], which indicate that this interaction may be retained. "
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    ABSTRACT: Background The current knowledge of eukaryote signalling originates from phenotypically diverse organisms. There is a pressing need to identify conserved signalling components among eukaryotes, which will lead to the transfer of knowledge across kingdoms. Two useful properties of a eukaryote model for signalling are (1) reduced signalling complexity, and (2) conservation of signalling components. The alga Ostreococcus tauri is described as the smallest free-living eukaryote. With less than 8,000 genes, it represents a highly constrained genomic palette. Results Our survey revealed 133 protein kinases and 34 protein phosphatases (1.7% and 0.4% of the proteome). We conducted phosphoproteomic experiments and constructed domain structures and phylogenies for the catalytic protein-kinases. For each of the major kinases families we review the completeness and divergence of O. tauri representatives in comparison to the well-studied kinomes of the laboratory models Arabidopsis thaliana and Saccharomyces cerevisiae, and of Homo sapiens. Many kinase clades in O. tauri were reduced to a single member, in preference to the loss of family diversity, whereas TKL and ABC1 clades were expanded. We also identified kinases that have been lost in A. thaliana but retained in O. tauri. For three, contrasting eukaryotic pathways – TOR, MAPK, and the circadian clock – we established the subset of conserved components and demonstrate conserved sites of substrate phosphorylation and kinase motifs. Conclusions We conclude that O. tauri satisfies our two central requirements. Several of its kinases are more closely related to H. sapiens orthologs than S. cerevisiae is to H. sapiens. The greatly reduced kinome of O. tauri is therefore a suitable model for signalling in free-living eukaryotes. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-640) contains supplementary material, which is available to authorized users.
    Full-text · Article · Aug 2014 · BMC Genomics
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