1
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Zhang H, Zhou Z, Guo J. The Function, Regulation, and Mechanism of Protein Turnover in Circadian Systems in Neurospora and Other Species. Int J Mol Sci 2024; 25:2574. [PMID: 38473819 DOI: 10.3390/ijms25052574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 02/18/2024] [Accepted: 02/20/2024] [Indexed: 03/14/2024] Open
Abstract
Circadian clocks drive a large array of physiological and behavioral activities. At the molecular level, circadian clocks are composed of positive and negative elements that form core oscillators generating the basic circadian rhythms. Over the course of the circadian period, circadian negative proteins undergo progressive hyperphosphorylation and eventually degrade, and their stability is finely controlled by complex post-translational pathways, including protein modifications, genetic codon preference, protein-protein interactions, chaperon-dependent conformation maintenance, degradation, etc. The effects of phosphorylation on the stability of circadian clock proteins are crucial for precisely determining protein function and turnover, and it has been proposed that the phosphorylation of core circadian clock proteins is tightly correlated with the circadian period. Nonetheless, recent studies have challenged this view. In this review, we summarize the research progress regarding the function, regulation, and mechanism of protein stability in the circadian clock systems of multiple model organisms, with an emphasis on Neurospora crassa, in which circadian mechanisms have been extensively investigated. Elucidation of the highly complex and dynamic regulation of protein stability in circadian clock networks would greatly benefit the integrated understanding of the function, regulation, and mechanism of protein stability in a wide spectrum of other biological processes.
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Affiliation(s)
- Haoran Zhang
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Zengxuan Zhou
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Jinhu Guo
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
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2
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Gabriel CH, Del Olmo M, Zehtabian A, Jäger M, Reischl S, van Dijk H, Ulbricht C, Rakhymzhan A, Korte T, Koller B, Grudziecki A, Maier B, Herrmann A, Niesner R, Zemojtel T, Ewers H, Granada AE, Herzel H, Kramer A. Live-cell imaging of circadian clock protein dynamics in CRISPR-generated knock-in cells. Nat Commun 2021; 12:3796. [PMID: 34145278 PMCID: PMC8213786 DOI: 10.1038/s41467-021-24086-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 05/25/2021] [Indexed: 02/06/2023] Open
Abstract
The cell biology of circadian clocks is still in its infancy. Here, we describe an efficient strategy for generating knock-in reporter cell lines using CRISPR technology that is particularly useful for genes expressed transiently or at low levels, such as those coding for circadian clock proteins. We generated single and double knock-in cells with endogenously expressed PER2 and CRY1 fused to fluorescent proteins allowing us to simultaneously monitor the dynamics of CRY1 and PER2 proteins in live single cells. Both proteins are highly rhythmic in the nucleus of human cells with PER2 showing a much higher amplitude than CRY1. Surprisingly, CRY1 protein is nuclear at all circadian times indicating the absence of circadian gating of nuclear import. Furthermore, in the nucleus of individual cells CRY1 abundance rhythms are phase-delayed (~5 hours), and CRY1 levels are much higher (>5 times) compared to PER2 questioning the current model of the circadian oscillator.
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Affiliation(s)
- Christian H Gabriel
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Marta Del Olmo
- Institute for Theoretical Biology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Amin Zehtabian
- Institute for Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Marten Jäger
- Berlin Institute of Health (BIH) Core Genomics Facility, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Silke Reischl
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Hannah van Dijk
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Carolin Ulbricht
- Immune Dynamics, Rheumatology and Clinical Immunology, Charité - Universitätsmedizin Berlin, Berlin, Germany
- Immune Dynamics, Deutsches Rheuma-Forschungszentrum (DRFZ), a Leibniz Institute, Berlin, Germany
| | - Asylkhan Rakhymzhan
- Biophysical Analytics, Deutsches Rheuma-Forschungszentrum (DRFZ), a Leibniz Institute, Berlin, Germany
| | - Thomas Korte
- Molecular Biophysics, Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany
| | - Barbara Koller
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Astrid Grudziecki
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Bert Maier
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany
- Berlin Institute of Health (BIH), Berlin, Germany
| | - Andreas Herrmann
- Molecular Biophysics, Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany
| | - Raluca Niesner
- Biophysical Analytics, Deutsches Rheuma-Forschungszentrum (DRFZ), a Leibniz Institute, Berlin, Germany
- Dynamic and Functional in vivo Imaging, Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Tomasz Zemojtel
- Berlin Institute of Health (BIH) Core Genomics Facility, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Helge Ewers
- Institute for Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Adrián E Granada
- Charité Comprehensive Cancer Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Hanspeter Herzel
- Institute for Theoretical Biology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Achim Kramer
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Laboratory of Chronobiology, Berlin, Germany.
- Berlin Institute of Health (BIH), Berlin, Germany.
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3
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Upadhyay A, Marzoll D, Diernfellner A, Brunner M, Herzel H. Multiple random phosphorylations in clock proteins provide long delays and switches. Sci Rep 2020; 10:22224. [PMID: 33335302 PMCID: PMC7746754 DOI: 10.1038/s41598-020-79277-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 11/25/2020] [Indexed: 12/27/2022] Open
Abstract
Theory predicts that self-sustained oscillations require robust delays and nonlinearities (ultrasensitivity). Delayed negative feedback loops with switch-like inhibition of transcription constitute the core of eukaryotic circadian clocks. The kinetics of core clock proteins such as PER2 in mammals and FRQ in Neurospora crassa is governed by multiple phosphorylations. We investigate how multiple, slow and random phosphorylations control delay and molecular switches. We model phosphorylations of intrinsically disordered clock proteins (IDPs) using conceptual models of sequential and distributive phosphorylations. Our models help to understand the underlying mechanisms leading to delays and ultrasensitivity. The model shows temporal and steady state switches for the free kinase and the phosphoprotein. We show that random phosphorylations and sequestration mechanisms allow high Hill coefficients required for self-sustained oscillations.
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Affiliation(s)
- Abhishek Upadhyay
- Institute for Theoretical Biology, Charité, Universitätsmedizin Berlin, Humboldt University of Berlin, Philippstr. 13, 10115, Berlin, Germany.
| | - Daniela Marzoll
- Biochemistry Center, University of Heidelberg, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Axel Diernfellner
- Biochemistry Center, University of Heidelberg, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Michael Brunner
- Biochemistry Center, University of Heidelberg, Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Hanspeter Herzel
- Institute for Theoretical Biology, Charité, Universitätsmedizin Berlin, Humboldt University of Berlin, Philippstr. 13, 10115, Berlin, Germany.
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4
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Diernfellner AC, Brunner M. Phosphorylation Timers in the Neurospora crassa Circadian Clock. J Mol Biol 2020; 432:3449-3465. [DOI: 10.1016/j.jmb.2020.04.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/10/2020] [Accepted: 04/05/2020] [Indexed: 02/08/2023]
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5
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Protein phosphatases regulate growth, development, cellulases and secondary metabolism in Trichoderma reesei. Sci Rep 2019; 9:10995. [PMID: 31358805 PMCID: PMC6662751 DOI: 10.1038/s41598-019-47421-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 07/03/2019] [Indexed: 12/15/2022] Open
Abstract
Trichoderma reesei represents one of the most prolific producers of plant cell wall degrading enzymes. Recent research showed broad regulation by phosphorylation in T. reesei, including important transcription factors involved in cellulase regulation. To evaluate factors crucial for changes in these phosphorylation events, we studied non-essential protein phosphatases (PPs) of T. reesei. Viable deletion strains were tested for growth on different carbon sources, osmotic and oxidative stress response, asexual and sexual development, cellulase and protease production as well as secondary metabolism. Six PPs were found to be positive or negative regulators for cellulase production. A correlation of the effects of PPs on protease activities and cellulase activities was not detected. Hierarchical clustering of regulation patterns and phenotypes of deletion indicated functional specialization within PP classes and common as well as variable effects. Our results confirmed the central role of catalytic and regulatory subunits of PP2A which regulates several aspects of cell growth and metabolism. Moreover we show that the additional homologue of PPH5 in Trichoderma spp., PPH5-2 assumes distinct functions in metabolism, development and stress response, different from PPH5. The influence of PPs on both cellulase gene expression and secondary metabolite production support an interrelationship in the underlying regulation mechanisms.
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6
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Gödel M. Entrainment memories: What does stable mean? Psych J 2018; 7:209-224. [PMID: 30561855 DOI: 10.1002/pchj.264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 10/29/2018] [Accepted: 11/06/2018] [Indexed: 11/07/2022]
Abstract
Diurnal environmental factors (zeitgebers) set the circadian clock in an antagonistic way: The body clock is tuned forward in the morning, while the same factor late in the day puts the body clock back to a later time-point: Morning light, for example, reduces the clock-effective light-reception (zeitnehmer2 ) by shifting the expression of the circadian, light-processing, molecular machinery more into the late, light-less night. Evening light does the same by a backward-shift, respectively. The balance between these daily back and forth adaptations results in a synchronization of the organismic timing with its environment. Those traditional models are challenged in this study. Using Neurospora as a model, I will explore how the entrainment process follows diverging trajectories depending on zeitgeber structure and strength, and the kind of transition between different entraining situations. The diverging routes of entrainment, systematically becoming earlier and earlier or later and later until eventually settling in distinct entrained phases, point out the existence of a long-range "memory" component. The view of entrainment as a non-acute reaction is very well confirmed in feedback loops, limit cycles, phase-response curves, and so forth. However, the presented findings enhance an extension of those concepts: The processing of zeitgebers by oscillating zeitnehmer modules resulting in a certain temporal inner structuring is not fully established within one repetition along a unique reaction norm. I hypothesize that the long-range, multi-cycle component in entraining requires a third parameter of description additional to current internal phase and zeitgeber condition, which originates from the differential of the two or more consecutive periodic situations. I hypothesize that this differential is represented by a gradient of Gibbs free energy of the entrainment pathways. Low points of free energy identify stable phases of entrainment. The fundamentality of Gibbs energy puts entrainment up for discussion not only as a timer but as an important kind of homeostasis.
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Affiliation(s)
- Manfred Gödel
- Institute of Medical Psychology, Ludwig Maximilian University, Munich, Germany
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7
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Park N, Song J, Jeong S, Thi Tran T, Ko HW, Kim EY. Vaccinia-related kinase 3 (VRK3) sets the circadian period and amplitude by affecting the subcellular localization of clock proteins in mammalian cells. Biochem Biophys Res Commun 2017; 487:320-326. [PMID: 28412365 DOI: 10.1016/j.bbrc.2017.04.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 04/09/2017] [Indexed: 11/26/2022]
Abstract
In the eukaryotic circadian clock machinery, negative feedback repression of CLOCK (CLK) and BMAL1 transcriptional activity by PERIOD (PER) and CRYPTOCHROME (CRY) underlies the basis for 24 h rhythmic gene expression. Thus, precise regulation of the time-dependent nuclear entry of circadian repressors is crucial to generating normal circadian rhythms. Here, we sought to identify novel kinase(s) that regulate nuclear entry of mammalian CRY1 (mCRY1) with an unbiased screening using red fluorescent protein (RFP)-tagged human kinome expression plasmids in mammalian cells. Transient expression of human vaccinia-related kinase 3 (hVRK3) reduced the nuclear presence of mCRY1. hVRK3 expression also induced alterations in the subcellular localization of other core clock proteins, including mCRY2, mPER2, and BMAL1. In contrast, the subcellular localization of mCLK was not changed. Given that singly expressed mCLK mostly resides in the cytoplasm and that nuclear localization sequence (NLS) mutation of hVRK3 attenuated the effect of hVRK3 co-expression on subcellular localization, ectopically expressed hVRK3 presumably reduces the retention of proteins in the nucleus. Finally, downregulation of hvrk3 using siRNA reduced the amplitude and lengthened the period of the cellular bioluminescence rhythm. Taken together, these data suggest that VRK3 plays a role in setting the amplitude and period length of circadian rhythms in mammalian cells.
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Affiliation(s)
- Nayoung Park
- Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea; Department of Brain Science, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea
| | - Jieun Song
- College of Pharmacy, Dongguk University-Seoul, 32 Donggukro, Ilsandonggu, Goyangsi, Gyeonggido, 410-820, Republic of Korea
| | - Seongsu Jeong
- Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea; Department of Brain Science, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea
| | - Thanh Thi Tran
- College of Pharmacy, Dongguk University-Seoul, 32 Donggukro, Ilsandonggu, Goyangsi, Gyeonggido, 410-820, Republic of Korea
| | - Hyuk Wan Ko
- College of Pharmacy, Dongguk University-Seoul, 32 Donggukro, Ilsandonggu, Goyangsi, Gyeonggido, 410-820, Republic of Korea
| | - Eun Young Kim
- Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea; Department of Brain Science, Ajou University School of Medicine, 164 Worldcup-ro, Yeongtong-gu, Suwon, Kyunggi-do, 16499, Republic of Korea.
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8
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Ay A, Holland J, Sperlea A, Devakanmalai GS, Knierer S, Sangervasi S, Stevenson A, Ozbudak EM. Spatial gradients of protein-level time delays set the pace of the traveling segmentation clock waves. Development 2014; 141:4158-67. [PMID: 25336742 DOI: 10.1242/dev.111930] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The vertebrate segmentation clock is a gene expression oscillator controlling rhythmic segmentation of the vertebral column during embryonic development. The period of oscillations becomes longer as cells are displaced along the posterior to anterior axis, which results in traveling waves of clock gene expression sweeping in the unsegmented tissue. Although various hypotheses necessitating the inclusion of additional regulatory genes into the core clock network at different spatial locations have been proposed, the mechanism underlying traveling waves has remained elusive. Here, we combined molecular-level computational modeling and quantitative experimentation to solve this puzzle. Our model predicts the existence of an increasing gradient of gene expression time delays along the posterior to anterior direction to recapitulate spatiotemporal profiles of the traveling segmentation clock waves in different genetic backgrounds in zebrafish. We validated this prediction by measuring an increased time delay of oscillatory Her1 protein production along the unsegmented tissue. Our results refuted the need for spatial expansion of the core feedback loop to explain the occurrence of traveling waves. Spatial regulation of gene expression time delays is a novel way of creating dynamic patterns; this is the first report demonstrating such a control mechanism in any tissue and future investigations will explore the presence of analogous examples in other biological systems.
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Affiliation(s)
- Ahmet Ay
- Department of Mathematics, Colgate University, Hamilton, NY 13346, USA Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Jack Holland
- Department of Computer Science, Colgate University, Hamilton, NY 13346, USA
| | - Adriana Sperlea
- Department of Computer Science, Colgate University, Hamilton, NY 13346, USA
| | | | - Stephan Knierer
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | - Angel Stevenson
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ertuğrul M Ozbudak
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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9
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Öllinger R, Korge S, Korte T, Koller B, Herrmann A, Kramer A. Dynamics of the circadian clock protein PERIOD2 in living cells. J Cell Sci 2014; 127:4322-8. [PMID: 25074809 DOI: 10.1242/jcs.156612] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In mammals, circadian rhythms are generated by delayed negative feedback, in which period (PER1-PER3) and cryptochrome (CRY1, CRY2) proteins gradually accumulate in the nucleus to suppress the transcription of their own genes. Although the importance of nuclear import and export signals for the subcellular localization of clock proteins is well established, little is known about the dynamics of these processes as well as their importance for the generation of circadian rhythms. We show by pharmacological perturbations of oscillating cells that nuclear import and export are of crucial importance for the circadian period. Live-cell fluorescence microscopy revealed that nuclear import of the key circadian protein PER2 is fast and further accelerated by CRY1. Moreover, PER2 nuclear import is crucially dependent on a specific nuclear-receptor-binding motif in PER2 that also mediates nuclear immobility. Nuclear export, however, is relatively slow, supporting a model of PER2 nuclear accumulation by rapid import, slow export and substantial nuclear degradation.
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Affiliation(s)
- Rupert Öllinger
- Laboratory of Chronobiology, Charité - Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany
| | - Sandra Korge
- Laboratory of Chronobiology, Charité - Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany
| | - Thomas Korte
- Department of Biology, Molecular Biophysics, Humboldt-University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany
| | - Barbara Koller
- Laboratory of Chronobiology, Charité - Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany
| | - Andreas Herrmann
- Department of Biology, Molecular Biophysics, Humboldt-University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany
| | - Achim Kramer
- Laboratory of Chronobiology, Charité - Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany
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10
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Kim J, Geng R, Gallenstein RA, Somers DE. The F-box protein ZEITLUPE controls stability and nucleocytoplasmic partitioning of GIGANTEA. Development 2013; 140:4060-9. [PMID: 24004949 DOI: 10.1242/dev.096651] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Nucleocytoplasmic partitioning of core clock components is essential for the proper operation of the circadian system. Previous work has shown that the F-box protein ZEITLUPE (ZTL) and clock element GIGANTEA (GI) heterodimerize in the cytosol, thereby stabilizing ZTL. Here, we report that ZTL post-translationally and reciprocally regulates protein levels and nucleocytoplasmic distribution of GI in Arabidopsis. We use ectopic expression of the N-terminus of ZTL, which contains the novel, light-absorbing region of ZTL (the LOV domain), transient expression assays and ztl mutants to establish that the levels of ZTL, a cytosolic protein, help govern the abundance and distribution of GI in the cytosol and nucleus. Ectopic expression of the ZTL N-terminus lengthens period, delays flowering time and alters hypocotyl length. We demonstrate that these phenotypes can be explained by the competitive interference of the LOV domain with endogenous GI-ZTL interactions. A complex of the ZTL N-terminus polypeptide with endogenous GI (LOV-GI) blocks normal GI function, causing degradation of endogenous ZTL and inhibition of other GI-related phenotypes. Increased cytosolic retention of GI by the LOV-GI complex additionally inhibits nuclear roles of GI, thereby lengthening flowering time. Hence, we conclude that under endogenous conditions, GI stabilization and cytoplasmic retention occurs naturally through a LOV domain-mediated GI-ZTL interaction, and that ZTL indirectly regulates GI nuclear pools by sequestering GI to the cytosol. As the absence of either GI or ZTL compromises clock function and diminishes the protein abundance of the other, our results highlight how their reciprocal co-stabilization is essential for robust circadian oscillations.
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Affiliation(s)
- Jeongsik Kim
- Department of Molecular Genetics, Ohio State University, Columbus, OH 43210, USA
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11
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Tataroğlu Ö, Lauinger L, Sancar G, Jakob K, Brunner M, Diernfellner ACR. Glycogen synthase kinase is a regulator of the circadian clock of Neurospora crassa. J Biol Chem 2012; 287:36936-43. [PMID: 22955278 DOI: 10.1074/jbc.m112.396622] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Timekeeping by circadian clocks relies upon precise adjustment of expression levels of clock proteins. Here we identify glycogen synthase kinase (GSK) as a novel and critical component of the circadian clock of Neurospora crassa that regulates the abundance of its core transcription factor white collar complex (WCC) on a post-transcriptional level. We show that GSK specifically binds and phosphorylates both subunits of the WCC. Reduced expression of GSK promotes an increased accumulation of WC-1, the limiting factor of the WCC, causing an acceleration of the circadian clock and a shorter free-running period.
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Affiliation(s)
- Özgür Tataroğlu
- Biochemistry Center, University of Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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12
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Spencer S, Torres-Altoro MI, Falcon E, Arey R, Marvin M, Goldberg M, Bibb JA, McClung CA. A mutation in CLOCK leads to altered dopamine receptor function. J Neurochem 2012; 123:124-34. [PMID: 22757753 DOI: 10.1111/j.1471-4159.2012.07857.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Mice with a mutation in the Clock gene (ClockΔ19) have a number of behavioral phenotypes that suggest alterations in dopaminergic transmission. These include hyperactivity, increased exploratory behavior, and increased reward value for drugs of abuse. However, the complex changes in dopaminergic transmission that underlie the behavioral abnormalities in these mice remain unclear. Here we find that a loss of CLOCK function increases dopamine release and turnover in striatum as indicated by increased levels of metabolites HVA and DOPAC, and enhances sensitivity to dopamine receptor antagonists. Interestingly, this enlarged dopaminergic tone results in downstream changes in dopamine receptor (DR) levels with a surprising augmentation of both D1- and D2-type DR protein, but a significant shift in the ratio of D1 : D2 receptors in favor of D2 receptor signaling. These effects have functional consequences for both behavior and intracellular signaling, with alterations in locomotor responses to both D1-type and D2-type specific agonists and a blunted response to cAMP activation in the ClockΔ19 mutants. Taken together, these studies further elucidate the abnormalities in dopaminergic transmission that underlie mood, activity, and addictive behaviors.
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Affiliation(s)
- Sade Spencer
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
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13
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Herrero E, Davis SJ. Time for a nuclear meeting: protein trafficking and chromatin dynamics intersect in the plant circadian system. MOLECULAR PLANT 2012; 5:554-565. [PMID: 22379122 DOI: 10.1093/mp/sss010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Circadian clocks mediate adaptation to the 24-h world. In Arabidopsis, most circadian-clock components act in the nucleus as transcriptional regulators and generate rhythmic oscillations of transcript accumulation. In this review, we focus on post-transcriptional events that modulate the activity of circadian-clock components, such as phosphorylation, ubiquitination and proteasome-mediated degradation, changes in cellular localization, and protein-protein interactions. These processes have been found to be essential for circadian function, not only in plants, but also in other circadian systems. Moreover, light and clock signaling networks are highly interconnected. In the nucleus, light and clock components work together to generate transcriptional rhythms, leading to a general control of the timing of plant physiological processes.
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Affiliation(s)
- Eva Herrero
- Max Planck Institute for Plant Breeding Research, Carl-von-Linnéweg 10, 50829 Cologne, Germany
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14
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Tataroğlu Ö, Schafmeier T. Of switches and hourglasses: regulation of subcellular traffic in circadian clocks by phosphorylation. EMBO Rep 2011. [DOI: 10.1038/embor.2011.71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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15
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Phosphorylations: making the Neurospora
crassa
circadian clock tick. FEBS Lett 2011; 585:1461-6. [DOI: 10.1016/j.febslet.2011.03.049] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 03/09/2011] [Accepted: 03/23/2011] [Indexed: 11/19/2022]
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16
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Kinases and phosphatases in the mammalian circadian clock. FEBS Lett 2011; 585:1393-9. [DOI: 10.1016/j.febslet.2011.02.038] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 02/23/2011] [Accepted: 02/28/2011] [Indexed: 12/28/2022]
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