1
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Kula-Eversole E, Lee DH, Samba I, Yildirim E, Levine DC, Hong HK, Lear BC, Bass J, Rosbash M, Allada R. Phosphatase of Regenerating Liver-1 Selectively Times Circadian Behavior in Darkness via Function in PDF Neurons and Dephosphorylation of TIMELESS. Curr Biol 2021; 31:138-149.e5. [PMID: 33157022 PMCID: PMC7855481 DOI: 10.1016/j.cub.2020.10.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 08/25/2020] [Accepted: 10/07/2020] [Indexed: 12/31/2022]
Abstract
The timing of behavior under natural light-dark conditions is a function of circadian clocks and photic input pathways, but a mechanistic understanding of how these pathways collaborate in animals is lacking. Here we demonstrate in Drosophila that the Phosphatase of Regenerating Liver-1 (PRL-1) sets period length and behavioral phase gated by photic signals. PRL-1 knockdown in PDF clock neurons dramatically lengthens circadian period. PRL-1 mutants exhibit allele-specific interactions with the light- and clock-regulated gene timeless (tim). Moreover, we show that PRL-1 promotes TIM accumulation and dephosphorylation. Interestingly, the PRL-1 mutant period lengthening is suppressed in constant light, and PRL-1 mutants display a delayed phase under short, but not long, photoperiod conditions. Thus, our studies reveal that PRL-1-dependent dephosphorylation of TIM is a core mechanism of the clock that sets period length and phase in darkness, enabling the behavioral adjustment to change day-night cycles.
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Affiliation(s)
| | - Da Hyun Lee
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Ima Samba
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Evrim Yildirim
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Daniel C Levine
- Department of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Hee-Kyung Hong
- Department of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Bridget C Lear
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Joseph Bass
- Department of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Michael Rosbash
- Howard Hughes Medical Institute, Department of Biology, Brandeis University, Waltham, MA 02445, USA
| | - Ravi Allada
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA.
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2
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Sabado V, Vienne L, Nagoshi E. Evaluating the Autonomy of the Drosophila Circadian Clock in Dissociated Neuronal Culture. Front Cell Neurosci 2017; 11:317. [PMID: 29075180 PMCID: PMC5643464 DOI: 10.3389/fncel.2017.00317] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/26/2017] [Indexed: 11/13/2022] Open
Abstract
Circadian behavioral rhythms offer an excellent model to study intricate interactions between the molecular and neuronal mechanisms of behavior. In mammals, pacemaker neurons in the suprachiasmatic nucleus (SCN) generate rhythms cell-autonomously, which are synchronized by the network interactions within the circadian circuit to drive behavioral rhythms. However, whether this principle is universal to circadian systems in animals remains unanswered. Here, we examined the autonomy of the Drosophila circadian clock by monitoring transcriptional and post-transcriptional rhythms of individual clock neurons in dispersed culture with time-lapse microscopy. Expression patterns of the transcriptional reporter show that CLOCK/CYCLE (CLK/CYC)-mediated transcription is constantly active in dissociated clock neurons. In contrast, the expression profile of the post-transcriptional reporter indicates that PERIOD (PER) protein levels fluctuate and ~10% of cells display rhythms in PER levels with periods in the circadian range. Nevertheless, PER and TIM are enriched in the cytoplasm and no periodic PER nuclear accumulation was observed. These results suggest that repression of CLK/CYC-mediated transcription by nuclear PER is impaired, and thus the negative feedback loop of the molecular clock is incomplete in isolated clock neurons. We further demonstrate that, by pharmacological assays using the non-amidated form of neuropeptide pigment-dispersing factor (PDF), which could be specifically secreted from larval LNvs and adult s-LNvs, downstream events of the PDF signaling are partly impaired in dissociated larval clock neurons. Although non-amidated PDF is likely to be less active than the amidated one, these results point out the possibility that alteration in PDF downstream signaling may play a role in dampening of molecular rhythms in isolated clock neurons. Taken together, our results suggest that Drosophila clocks are weak oscillators that need to be in the intact circadian circuit to generate robust 24-h rhythms.
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Affiliation(s)
- Virginie Sabado
- Department of Genetics and Evolution, Sciences III, University of Geneva, Geneva, Switzerland
| | - Ludovic Vienne
- Department of Genetics and Evolution, Sciences III, University of Geneva, Geneva, Switzerland
| | - Emi Nagoshi
- Department of Genetics and Evolution, Sciences III, University of Geneva, Geneva, Switzerland
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3
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Mahesh G, Jeong E, Ng FS, Liu Y, Gunawardhana K, Houl JH, Yildirim E, Amunugama R, Jones R, Allen DL, Edery I, Kim EY, Hardin PE. Phosphorylation of the transcription activator CLOCK regulates progression through a ∼ 24-h feedback loop to influence the circadian period in Drosophila. J Biol Chem 2014; 289:19681-93. [PMID: 24872414 DOI: 10.1074/jbc.m114.568493] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Circadian (≅ 24 h) clocks control daily rhythms in metabolism, physiology, and behavior in animals, plants, and microbes. In Drosophila, these clocks keep circadian time via transcriptional feedback loops in which clock-cycle (CLK-CYC) initiates transcription of period (per) and timeless (tim), accumulating levels of PER and TIM proteins feed back to inhibit CLK-CYC, and degradation of PER and TIM allows CLK-CYC to initiate the next cycle of transcription. The timing of key events in this feedback loop are controlled by, or coincide with, rhythms in PER and CLK phosphorylation, where PER and CLK phosphorylation is high during transcriptional repression. PER phosphorylation at specific sites controls its subcellular localization, activity, and stability, but comparatively little is known about the identity and function of CLK phosphorylation sites. Here we identify eight CLK phosphorylation sites via mass spectrometry and determine how phosphorylation at these sites impacts behavioral and molecular rhythms by transgenic rescue of a new Clk null mutant. Eliminating phosphorylation at four of these sites accelerates the feedback loop to shorten the circadian period, whereas loss of CLK phosphorylation at serine 859 increases CLK activity, thereby increasing PER levels and accelerating transcriptional repression. These results demonstrate that CLK phosphorylation influences the circadian period by regulating CLK activity and progression through the feedback loop.
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Affiliation(s)
- Guruswamy Mahesh
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843
| | - EunHee Jeong
- the Department of Brain Science, Ajou University School of Medicine, Suwon 443-380, Korea
| | - Fanny S Ng
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843
| | - Yixiao Liu
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843
| | - Kushan Gunawardhana
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843
| | - Jerry H Houl
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843
| | - Evrim Yildirim
- the Department of Molecular Biology and Biochemistry, Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway New Jersey 08854
| | | | | | | | - Isaac Edery
- the Department of Molecular Biology and Biochemistry, Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway New Jersey 08854
| | - Eun Young Kim
- the Department of Brain Science, Ajou University School of Medicine, Suwon 443-380, Korea
| | - Paul E Hardin
- From the Department of Biology and Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77843,
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4
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PDF and cAMP enhance PER stability in Drosophila clock neurons. Proc Natl Acad Sci U S A 2014; 111:E1284-90. [PMID: 24707054 DOI: 10.1073/pnas.1402562111] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The neuropeptide PDF is important for Drosophila circadian rhythms: pdf(01) (pdf-null) animals are mostly arrhythmic or short period in constant darkness and have an advanced activity peak in light-dark conditions. PDF contributes to the amplitude, synchrony, as well as the pace of circadian rhythms within clock neurons. PDF is known to increase cAMP levels in PDR receptor (PDFR)-containing neurons. However, there is no known connection of PDF or of cAMP with the Drosophila molecular clockworks. We discovered that the mutant period gene per(S) ameliorates the phenotypes of pdf-null flies. The period protein (PER) is a well-studied repressor of clock gene transcription, and the per(S) protein (PERS) has a markedly short half-life. The result therefore suggests that the PDF-mediated increase in cAMP might lengthen circadian period by directly enhancing PER stability. Indeed, increasing cAMP levels and cAMP-mediated protein kinase A (PKA) activity stabilizes PER, in S2 tissue culture cells and in fly circadian neurons. Adding PDF to fly brains in vitro has a similar effect. Consistent with these relationships, a light pulse causes more prominent PER degradation in pdf(01) circadian neurons than in wild-type neurons. The results indicate that PDF contributes to clock neuron synchrony by increasing cAMP and PKA, which enhance PER stability and decrease clock speed in intrinsically fast-paced PDFR-containing clock neurons. We further suggest that the more rapid degradation of PERS bypasses PKA regulation and makes the pace of clock neurons more uniform, allowing them to avoid much of the asynchrony caused by the absence of PDF.
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5
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Li Y, Rosbash M. Accelerated degradation of perS protein provides insight into light-mediated phase shifting. J Biol Rhythms 2013; 28:171-82. [PMID: 23735496 DOI: 10.1177/0748730413489797] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Phase resetting by light is an important feature of circadian rhythms, and the current Drosophila model focuses on light-mediated degradation of the clock protein TIMELESS (TIM). PERIOD (PER) is the binding partner of TIM and a major repressor of the molecular clock, but direct evidence of PER in phase resetting is lacking. Because light sensitivity of the per(S) short period mutant strain is strongly enhanced compared with wild-type strains, we assayed the importance of PER degradation for light-induced phase shifting. The per(S) protein (PERS) is markedly less stable than wild-type PER, in tissue culture and in flies, and PERS as well as PER is stabilized by TIM in both systems. Consistent with this finding, light-induced TIM degradation appears to trigger PER degradation. Moreover, TIM degradation is similar in the clock neurons of both strains, suggesting that it is not strongly affected by PERS and does not dictate the difference in the light response. In contrast, there is a dramatic quantitative difference between PER and PERS degradation in these neurons, indicating that PER degradation dictates the enhanced amplitude of the light-induced phase response. The data indicate that TIM inhibits PER degradation and that PER degradation follows light-mediated TIM degradation within circadian neurons; PER degradation then dictates qualitative as well as quantitative features of light-mediated phase-resetting.
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Affiliation(s)
- Yue Li
- Brandeis University, Waltham, MA 02454, USA
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6
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Szabó Á, Papin C, Zorn D, Ponien P, Weber F, Raabe T, Rouyer F. The CK2 kinase stabilizes CLOCK and represses its activity in the Drosophila circadian oscillator. PLoS Biol 2013; 11:e1001645. [PMID: 24013921 PMCID: PMC3754892 DOI: 10.1371/journal.pbio.1001645] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 07/19/2013] [Indexed: 12/21/2022] Open
Abstract
Phosphorylation is a pivotal regulatory mechanism for protein stability and activity in circadian clocks regardless of their evolutionary origin. It determines the speed and strength of molecular oscillations by acting on transcriptional activators and their repressors, which form negative feedback loops. In Drosophila, the CK2 kinase phosphorylates and destabilizes the PERIOD (PER) and TIMELESS (TIM) proteins, which inhibit CLOCK (CLK) transcriptional activity. Here we show that CK2 also targets the CLK activator directly. Downregulating the activity of the catalytic α subunit of CK2 induces CLK degradation, even in the absence of PER and TIM. Unexpectedly, the regulatory β subunit of the CK2 holoenzyme is not required for the regulation of CLK stability. In addition, downregulation of CK2α activity decreases CLK phosphorylation and increases per and tim transcription. These results indicate that CK2 inhibits CLK degradation while reducing its activity. Since the CK1 kinase promotes CLK degradation, we suggest that CLK stability and transcriptional activity result from counteracting effects of CK1 and CK2.
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Affiliation(s)
- Áron Szabó
- Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique Unité Propre de Recherche 3294, Gif-sur-Yvette, France
- Département de Biologie, Université Paris Sud, Orsay, France
| | - Christian Papin
- Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique Unité Propre de Recherche 3294, Gif-sur-Yvette, France
- Département de Biologie, Université Paris Sud, Orsay, France
| | - Daniela Zorn
- Heidelberg University, Biochemistry Center (BZH), Im Neuenheimer Feld 328, Heidelberg, Germany
| | - Prishila Ponien
- Institut de Chimie des Substances Naturelles, CNRS UPR2301, Gif-sur-Yvette, France
- IMAGIF, Centre de Recherche de Gif, Gif-sur-Yvette, France
| | - Frank Weber
- Heidelberg University, Biochemistry Center (BZH), Im Neuenheimer Feld 328, Heidelberg, Germany
| | - Thomas Raabe
- University of Wuerzburg, Institute of Medical Radiation and Cell Research, Wuerzburg, Germany
| | - François Rouyer
- Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique Unité Propre de Recherche 3294, Gif-sur-Yvette, France
- Département de Biologie, Université Paris Sud, Orsay, France
- * E-mail:
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7
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Luo W, Li Y, Tang CHA, Abruzzi KC, Rodriguez J, Pescatore S, Rosbash M. CLOCK deubiquitylation by USP8 inhibits CLK/CYC transcription in Drosophila. Genes Dev 2013; 26:2536-49. [PMID: 23154984 DOI: 10.1101/gad.200584.112] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A conserved transcriptional feedback loop underlies animal circadian rhythms. In Drosophila, the transcription factors CLOCK (CLK) and CYCLE (CYC) activate the transcription of direct target genes like period (per) and timeless (tim). They encode the proteins PER and TIM, respectively, which repress CLK/CYC activity. Previous work indicates that repression is due to a direct PER-CLK/CYC interaction as well as CLK/CYC phosphorylation. We describe here the role of ubiquitin-specific protease 8 (USP8) in circadian transcriptional repression as well as the importance of CLK ubiquitylation in CLK/CYC transcription activity. usp8 loss of function (RNAi) or expression of a dominant-negative form of the protein (USP8-DN) enhances CLK/CYC transcriptional activity and alters fly locomotor activity rhythms. Clock protein and mRNA molecular oscillations are virtually absent within circadian neurons of USP8-DN flies. Furthermore, CLK ubiquitylation cycles robustly in wild-type flies and peaks coincident with maximal CLK/CYC transcription. As USP8 interacts with CLK and expression of USP8-DN increases CLK ubiquitylation, the data indicate that USP8 deubiquitylates CLK, which down-regulates CLK/CYC transcriptional activity. Taken together with the facts that usp8 mRNA cycles and that its transcription is activated directly by CLK/CYC, USP8, like PER and TIM, contributes to the transcriptional feedback loop cycle that underlies circadian rhythms.
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8
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Khodor YL, Rodriguez J, Abruzzi KC, Tang CHA, Marr MT, Rosbash M. Nascent-seq indicates widespread cotranscriptional pre-mRNA splicing in Drosophila. Genes Dev 2012; 25:2502-12. [PMID: 22156210 DOI: 10.1101/gad.178962.111] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To determine the prevalence of cotranscriptional splicing in Drosophila, we sequenced nascent RNA transcripts from Drosophila S2 cells as well as from Drosophila heads. Eighty-seven percent of the introns assayed manifest >50% cotranscriptional splicing. The remaining 13% are cotranscriptionally spliced poorly or slowly, with ∼3% being almost completely retained in nascent pre-mRNA. Although individual introns showed slight but statistically significant differences in splicing efficiency, similar global levels of splicing were seen from both sources. Importantly, introns with low cotranscriptional splicing efficiencies are present in the same primary transcript with efficiently spliced introns, indicating that splicing is intron-specific. The analysis also indicates that cotranscriptional splicing is less efficient for first introns, longer introns, and introns annotated as alternative. Finally, S2 cells expressing the slow RpII215(C4) mutant show substantially less intron retention than wild-type S2 cells.
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Affiliation(s)
- Yevgenia L Khodor
- Howard Hughes Medical Institute, National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
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9
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Choi C, Lee J, Lim C, Jang D, Choe J. The DOUBLETIME protein kinase regulates phosphorylation of the Drosophila PDP1epsilon. J Neurochem 2009; 111:264-73. [PMID: 19663814 DOI: 10.1111/j.1471-4159.2009.06327.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reversible phosphorylation of clock proteins plays an important role in circadian timekeeping as it is a key post-translational mechanism that regulates the activity, stability and subcellular localization of core clock proteins. The kinase DOUBLETIME (DBT), a Drosophila ortholog of mammalian casein kinase Iepsilon, regulates circadian phosphorylation of two essential clock proteins, PERIOD and dCLOCK. We present evidence that Par Domain Protein 1epsilon (PDP1epsilon), a transcription factor and mediator of clock output in Drosophila, is phosphorylated in vivo and in cultured cells by DBT activity. We also demonstrate that DBT interacts with PDP1epsilon and promotes its degradation by the ubiquitin-proteasome pathway in cultured cells. In addition, PDP1epsilon nuclear localization is decreased by dbt RNA interference in S2 cell system. These results suggest that DBT regulates phosphorylation, stability and localization of PDP1epsilon, and that it has multiple targets in the Drosophila circadian system.
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Affiliation(s)
- Changtaek Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
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10
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Kadener S, Rodriguez J, Abruzzi KC, Khodor YL, Sugino K, Marr MT, Nelson S, Rosbash M. Genome-wide identification of targets of the drosha-pasha/DGCR8 complex. RNA (NEW YORK, N.Y.) 2009; 15:537-45. [PMID: 19223442 PMCID: PMC2661833 DOI: 10.1261/rna.1319309] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 12/18/2008] [Indexed: 05/24/2023]
Abstract
Drosha is a type III RNase, which plays a critical role in miRNA biogenesis. Drosha and its double-stranded RNA-binding partner protein Pasha/DGCR8 likely recognize and cleave miRNA precursor RNAs or pri-miRNA hairpins cotranscriptionally. To identify RNAs processed by Drosha, we used tiling microarrays to examine transcripts after depletion of drosha mRNA with dsRNA in Drosophila Schneider S2 cells. This strategy identified 137 Drosha-regulated RNAs, including 11 putative pri-miRNAs comprising 15 annotated miRNAs. Most of the identified pri-miRNAs seem extremely large, >10 kb as revealed by both the Drosha knock-down strategy and by RNA PolII chromatin IP followed by Drosophila tiling microarrays. Surprisingly, more than a hundred additional RNAs not annotated as miRNAs are under Drosha control and are likely to be direct targets of Drosha action. This is because many of them encode annotated genes, and unlike bona fide pri-miRNAs, they are not affected by depletion of the miRNA processing factor, dicer-1. Moreover, application of the evofold analysis software indicates that at least 25 of the Drosha-regulated RNAs contain evolutionarily conserved hairpins similar to those recognized by the Drosha-Pasha/DGCR8 complex in pri-miRNAs. One of these hairpins is located in the 5' UTR of both pasha and mammalian DGCR8. These observations suggest that a negative feedback loop acting on pasha mRNA may regulate the miRNA-biogenesis pathway: i.e., excess Drosha cleaves pasha/DGCR8 primary transcripts and leads to a reduction in pasha/DGCR8 mRNA levels and Pasha/DGCR8 synthesis.
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Affiliation(s)
- Sebastian Kadener
- Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02454, USA
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11
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Saez L, Meyer P, Young MW. A PER/TIM/DBT interval timer for Drosophila's circadian clock. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2008; 72:69-74. [PMID: 18419263 DOI: 10.1101/sqb.2007.72.034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Circadian rhythms in Drosophila are supported by a negative feedback loop, in which PERIOD (PER) and Timeless (TIM) shut down their own transcription as they translocate once a day from the cytoplasm of clock-containing cells to the nucleus. Period length is partially determined by an interval of cytoplasmic retention of the TIM and PER proteins. To study this process, we examined PER/TIM/Doubletime (DBT) physical interactions and nuclear translocation by imaging individual cultured Drosophila cells. Using live cell video microscopy and green fluorescent protein (GFP) tags, we observed dynamic patterns of stability and localization for DBT, PER, and TIM that resembled those previously found in vivo. These studies suggest that a cytoplasmic interval timer regulates nuclear translocation of these proteins. The cultured cell assay provides a potent system to study interactions among new and known genes involved in the generation of circadian behavior.
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Affiliation(s)
- L Saez
- Laboratory of Genetics, The Rockefeller University, New York, New York 10021, USA
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12
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Kadener S, Stoleru D, McDonald M, Nawathean P, Rosbash M. Clockwork Orange is a transcriptional repressor and a new Drosophila circadian pacemaker component. Genes Dev 2007; 21:1675-86. [PMID: 17578907 PMCID: PMC1899475 DOI: 10.1101/gad.1552607] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Many organisms use circadian clocks to keep temporal order and anticipate daily environmental changes. In Drosophila, the master clock gene Clock promotes the transcription of several key target genes. Two of these gene products, PER and TIM, repress CLK-CYC-mediated transcription. To recognize additional direct CLK target genes, we designed a genome-wide approach and identified clockwork orange (cwo) as a new core clock component. cwo encodes a transcriptional repressor that synergizes with PER and inhibits CLK-mediated activation. Consistent with this function, the mRNA profiles of CLK direct target genes in cwo mutant flies manifest high trough values and low amplitude oscillations. Because behavioral rhythmicity fails to persist in constant darkness (DD) with little or no effect on average mRNA levels in flies lacking cwo, transcriptional oscillation amplitude appears to be linked to rhythmicity. Moreover, the mutant flies are long period, consistent with the late repression indicated by the RNA profiles. These findings suggest that CWO acts preferentially in the late night to help terminate CLK-CYC-mediated transcription of direct target genes including cwo itself. The presence of mammalian homologs with circadian expression features (Dec1 and Dec2) suggests that a similar feedback mechanism exists in mammalian clocks.
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Affiliation(s)
- Sebastian Kadener
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Dan Stoleru
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
- Howard Hughes Medical Institute and National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Michael McDonald
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Pipat Nawathean
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
- Howard Hughes Medical Institute and National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Michael Rosbash
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
- Howard Hughes Medical Institute and National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
- Corresponding author.E-MAIL ; FAX (781) 736-3164
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13
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Nawathean P, Stoleru D, Rosbash M. A small conserved domain of Drosophila PERIOD is important for circadian phosphorylation, nuclear localization, and transcriptional repressor activity. Mol Cell Biol 2007; 27:5002-13. [PMID: 17452453 PMCID: PMC1951469 DOI: 10.1128/mcb.02338-06] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We identify in this study a 27-amino-acid motif which is conserved between the Drosophila melanogaster period protein (PER) and the three mammalian PERs. Characterization of PER lacking this motif (PER Delta) shows that it is important for phosphorylation of Drosophila PER by casein kinase I epsilon (CKI epsilon; doubletime protein or DBT) and CKII. S2 cell assays indicate that the domain also contributes significantly to PER nuclear localization as well as to PER transcriptional repressor activity. These two phenomena appear linked, since PER Delta transcriptional repressor activity in S2 cells was restored when nuclear localization was facilitated. Two less direct assays of PER Delta activity in flies can be interpreted similarly. The separate assay of nuclear import and export suggests that the domain functions in part to facilitate PER phosphorylation within the cytoplasm, which in turn promotes nuclear entry. As there is evidence that the kinases also function within the nucleus to promote transcriptional repression, we suggest that there is a subsequent collaboration between phosphorylated PER and the kinases to repress CLK-CYC activity, probably through the phosphorylation of CLK. This is then followed by additional PER phosphorylation, which occurs within the nucleus and leads to PER degradation.
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Affiliation(s)
- Pipat Nawathean
- Howard Hughes Medical Institute and Department of Biology, Brandeis University, Waltham, MA 02454, USA
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14
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Stoleru D, Nawathean P, Fernández MDLP, Menet JS, Ceriani MF, Rosbash M. The Drosophila Circadian Network Is a Seasonal Timer. Cell 2007; 129:207-19. [PMID: 17418796 DOI: 10.1016/j.cell.2007.02.038] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 01/08/2007] [Accepted: 02/16/2007] [Indexed: 10/23/2022]
Abstract
Previous work in Drosophila has defined two populations of circadian brain neurons, morning cells (M-cells) and evening cells (E-cells), both of which keep circadian time and regulate morning and evening activity, respectively. It has long been speculated that a multiple oscillator circadian network in animals underlies the behavioral and physiological pattern variability caused by seasonal fluctuations of photoperiod. We have manipulated separately the circadian photoentrainment pathway within E- and M-cells and show that E-cells process light information and function as master clocks in the presence of light. M-cells in contrast need darkness to cycle autonomously and dominate the network. The results indicate that the network switches control between these two centers as a function of photoperiod. Together with the different entraining properties of the two clock centers, the results suggest that the functional organization of the network underlies the behavioral adjustment to variations in daylength and season.
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Affiliation(s)
- Dan Stoleru
- Howard Hughes Medical Institute and National Center for Behavioral Genomics, Department of Biology, Brandeis University, Waltham, MA 02454, USA
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15
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Collins B, Blau J. Even a stopped clock tells the right time twice a day: circadian timekeeping in Drosophila. Pflugers Arch 2007; 454:857-67. [PMID: 17226053 DOI: 10.1007/s00424-006-0188-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Accepted: 11/03/2006] [Indexed: 11/30/2022]
Abstract
"Even a stopped clock tells the right time twice a day, and for once I'm inclined to believe Withnail is right. We are indeed drifting into the arena of the unwell... What we need is harmony. Fresh air. Stuff like that" "Bruce Robinson (1986, ref. 1)". Although a stopped Drosophila clock probably does not tell the right time even once a day, recent findings have demonstrated that accurate circadian time-keeping is dependent on harmony between groups of clock neurons within the brain. Furthermore, when harmony between the environment and the endogenous clock is lost, as during jet lag, we definitely feel unwell. In this review, we provide an overview of the current understanding of circadian rhythms in Drosophila, focussing on recent discoveries that demonstrate how approximately 100 neurons within the Drosophila brain control the behaviour of the whole fly, and how these rhythms respond to the environment.
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MESH Headings
- Adaptation, Biological/genetics
- Adaptation, Biological/physiology
- Adaptation, Biological/radiation effects
- Animals
- Biological Clocks/physiology
- Biological Clocks/radiation effects
- Circadian Rhythm/physiology
- Circadian Rhythm/radiation effects
- Drosophila/anatomy & histology
- Drosophila/physiology
- Drosophila Proteins/physiology
- Drosophila Proteins/radiation effects
- Feedback, Physiological
- Genes, Insect/physiology
- Light
- Models, Neurological
- Mutagenesis, Site-Directed
- Nerve Net/physiology
- Nerve Net/radiation effects
- Photoreceptor Cells, Invertebrate/cytology
- Photoreceptor Cells, Invertebrate/physiology
- Photoreceptor Cells, Invertebrate/radiation effects
- Thermosensing/genetics
- Thermosensing/physiology
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Affiliation(s)
- Ben Collins
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
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16
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Meyer P, Saez L, Young MW. PER-TIM interactions in living Drosophila cells: an interval timer for the circadian clock. Science 2006; 311:226-9. [PMID: 16410523 DOI: 10.1126/science.1118126] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In contrast to current models, fluorescence resonance energy transfer measurements using a single-cell imaging assay with fluorescent forms of PER and TIM showed that these proteins bind rapidly and persist in the cytoplasm while gradually accumulating in discrete foci. After approximately 6 hours, complexes abruptly dissociated, as PER and TIM independently moved to the nucleus in a narrow time frame. The per(L) mutation delayed nuclear accumulation in vivo and in our cultured cell system, but without affecting rates of PER/TIM assembly or dissociation. This finding points to a previously unrecognized form of temporal regulation that underlies the periodicity of the circadian clock.
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Affiliation(s)
- Pablo Meyer
- Laboratory of Genetics, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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17
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Guo Y, Jangi S, Welte MA. Organelle-specific control of intracellular transport: distinctly targeted isoforms of the regulator Klar. Mol Biol Cell 2005; 16:1406-16. [PMID: 15647372 PMCID: PMC551502 DOI: 10.1091/mbc.e04-10-0920] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Revised: 12/22/2004] [Accepted: 12/30/2004] [Indexed: 01/22/2023] Open
Abstract
Microtubule-based transport in cells is powered by a small set of distinct motors, yet timing and destination of transport can be controlled in a cargo-specific manner. The mechanistic basis for this specificity is not understood. To address this question, we analyzed the Drosophila Klarsicht (Klar) protein that regulates distinct microtubule-based transport processes. We find that localization of Klar to its cargoes is crucial for Klar function. Using mutations, we identify functionally important regions of Klar that confer distinct cargo specificity. In ovaries, Klar is present on the nuclear envelope, a localization that requires the C-terminal KASH domain. In early embryos, Klar is attached to lipid droplets, a localization mediated by a novel C-terminal domain encoded by an alternatively spliced exon. In cultured cells, these two domains are sufficient for targeting to the correct intracellular location. Our analysis disentangles Klar's modular organization: we propose that a core region integral to motor regulation is attached to variable domains so that the cell can target regulators with overlapping, yet distinct functions to specific cargoes. Such isoform variation may be a general strategy for adapting a common regulatory mechanism to specifically control motion and positioning of multiple organelles.
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Affiliation(s)
- Yi Guo
- Rosenstiel Biomedical Research Center, Brandeis University, Waltham, MA 02454, USA
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