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Castillo KD, Chapa ED, Lamb TM, Gangopadhyay M, Bell-Pedersen D. Circadian clock control of tRNA synthetases in Neurospora crassa. F1000Res 2023; 11:1556. [PMID: 37841830 PMCID: PMC10576190 DOI: 10.12688/f1000research.125351.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/31/2023] [Indexed: 10/17/2023] Open
Abstract
Background: In Neurospora crassa, the circadian clock controls rhythmic mRNA translation initiation through regulation of the eIF2α kinase CPC-3 (the homolog of yeast and mammalian GCN2). Active CPC-3 phosphorylates and inactivates eIF2α, leading to higher phosphorylated eIF2α (P-eIF2α) levels and reduced translation initiation during the subjective day. This daytime activation of CPC-3 is driven by its binding to uncharged tRNA, and uncharged tRNA levels peak during the day under control of the circadian clock. The daily rhythm in uncharged tRNA levels could arise from rhythmic amino acid levels or aminoacyl-tRNA synthetase (aaRSs) levels. Methods: To determine if and how the clock potentially controls rhythms in aspartyl-tRNA synthetase (AspRS) and glutaminyl-tRNA synthetase (GlnRS), both observed to be rhythmic in circadian genomic datasets, transcriptional and translational fusions to luciferase were generated. These luciferase reporter fusions were examined in wild type (WT), clock mutant Δ frq, and clock-controlled transcription factor deletion strains. Results: Translational and transcriptional fusions of AspRS and GlnRS to luciferase confirmed that their protein levels are clock-controlled with peak levels at night. Moreover, clock-controlled transcription factors NCU00275 and ADV-1 drive robust rhythmic protein expression of AspRS and GlnRS, respectively. Conclusions: These data support a model whereby coordinate clock control of select aaRSs drives rhythms in uncharged tRNAs, leading to rhythmic CPC-3 activation, and rhythms in translation of specific mRNAs.
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Affiliation(s)
- Kathrina D. Castillo
- Biology, Texas A&M University, College Station, TX, 77843, USA
- Center for Biological Clocks Research, Texas A&M University, College Station, TX, 77843, USA
| | - Emily D. Chapa
- Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Teresa M. Lamb
- Biology, Texas A&M University, College Station, TX, 77843, USA
- Center for Biological Clocks Research, Texas A&M University, College Station, TX, 77843, USA
| | - Madhusree Gangopadhyay
- Biology, Texas A&M University, College Station, TX, 77843, USA
- Center for Biological Clocks Research, Texas A&M University, College Station, TX, 77843, USA
| | - Deborah Bell-Pedersen
- Biology, Texas A&M University, College Station, TX, 77843, USA
- Center for Biological Clocks Research, Texas A&M University, College Station, TX, 77843, USA
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2
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Castillo KD, Wu C, Ding Z, Lopez-Garcia OK, Rowlinson E, Sachs MS, Bell-Pedersen D. A circadian clock translational control mechanism targets specific mRNAs to cytoplasmic messenger ribonucleoprotein granules. Cell Rep 2022; 41:111879. [PMID: 36577368 PMCID: PMC10241597 DOI: 10.1016/j.celrep.2022.111879] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 09/13/2022] [Accepted: 12/04/2022] [Indexed: 12/29/2022] Open
Abstract
Phosphorylation of Neurospora crassa eukaryotic initiation factor 2 α (eIF2α), a conserved translation initiation factor, is clock controlled. To determine the impact of rhythmic eIF2α phosphorylation on translation, we performed temporal ribosome profiling and RNA sequencing (RNA-seq) in wild-type (WT), clock mutant Δfrq, eIF2α kinase mutant Δcpc-3, and constitutively active cpc-3c cells. About 14% of mRNAs are rhythmically translated in WT cells, and translation rhythms for ∼30% of these mRNAs, which we named circadian translation-initiation-controlled genes (cTICs), are dependent on the clock and CPC-3. Most cTICs are expressed from arrhythmic mRNAs and contain a P-body (PB) localization motif in their 5' leader sequence. Deletion of SNR-1, a component of cytoplasmic messenger ribonucleoprotein granules (cmRNPgs) that include PBs and stress granules (SGs), and the PB motif on one of the cTIC mRNAs, zip-1, significantly alters zip-1 rhythmic translation. These results reveal that the clock regulates rhythmic translation of specific mRNAs through rhythmic eIF2α activity and cmRNPg metabolism.
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Affiliation(s)
- Kathrina D Castillo
- Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843, USA; Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Cheng Wu
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Zhaolan Ding
- Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843, USA; Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | | | - Emma Rowlinson
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Deborah Bell-Pedersen
- Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843, USA; Department of Biology, Texas A&M University, College Station, TX 77843, USA.
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3
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Shen L, Su Z, Yang K, Wu C, Becker T, Bell-Pedersen D, Zhang J, Sachs MS. Structure of the translating Neurospora ribosome arrested by cycloheximide. Proc Natl Acad Sci U S A 2021; 118:e2111862118. [PMID: 34815343 PMCID: PMC8640747 DOI: 10.1073/pnas.2111862118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2021] [Indexed: 11/18/2022] Open
Abstract
Ribosomes translate RNA into proteins. The protein synthesis inhibitor cycloheximide (CHX) is widely used to inhibit eukaryotic ribosomes engaged in translation elongation. However, the lack of structural data for actively translating polyribosomes stalled by CHX leaves unanswered the question of which elongation step is inhibited. We elucidated CHX's mechanism of action based on the cryo-electron microscopy structure of actively translating Neurospora crassa ribosomes bound with CHX at 2.7-Å resolution. The ribosome structure from this filamentous fungus contains clearly resolved ribosomal protein eL28, like higher eukaryotes but unlike budding yeast, which lacks eL28. Despite some differences in overall structures, the ribosomes from Neurospora, yeast, and humans all contain a highly conserved CHX binding site. We also sequenced classic Neurospora CHX-resistant alleles. These mutations, including one at a residue not previously observed to affect CHX resistance in eukaryotes, were in the large subunit proteins uL15 and eL42 that are part of the CHX-binding pocket. In addition to A-site transfer RNA (tRNA), P-site tRNA, messenger RNA, and CHX that are associated with the translating N. crassa ribosome, spermidine is present near the CHX binding site close to the E site on the large subunit. The tRNAs in the peptidyl transferase center are in the A/A site and the P/P site. The nascent peptide is attached to the A-site tRNA and not to the P-site tRNA. The structural and functional data obtained show that CHX arrests the ribosome in the classical PRE translocation state and does not interfere with A-site reactivity.
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Affiliation(s)
- Lunda Shen
- Department of Biology, Texas A&M University, College Station, TX 77843
| | - Zhaoming Su
- Department of Bioengineering, Stanford University, Stanford, CA 94305
| | - Kailu Yang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843
| | - Cheng Wu
- Department of Biology, Texas A&M University, College Station, TX 77843
| | - Thomas Becker
- Department of Biochemistry, Gene Center, Ludwig-Maximilians University Munich, 80539 Munich, Germany
| | | | - Junjie Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843
| | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, TX 77843;
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4
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Maity AK, Lee SC, Hu L, Bell-Pedersen D, Mallick BK, Sarkar TR. Circadian Gene Selection for Time-to-event Phenotype by Integrating CNV and RNAseq Data. Chemometr Intell Lab Syst 2021; 212:104276. [PMID: 35068632 PMCID: PMC8775911 DOI: 10.1016/j.chemolab.2021.104276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
BACKGROUND The endogenous circadian clock, which controls daily rhythms in the expression of at least half of the mammalian genome, has a major influence on cell physiology. Consequently, disruption of the circadian system is associated with wide range of diseases including cancer. While several circadian clock genes have been associated with cancer progression, little is known about the survival when two or more platforms are considered together. Our goal was to determine if survival outcomes are associated with circadian clock function. To accomplish this goal, we developed a Bayesian hierarchical survival model coupled with the global local shrinkage prior and applied this model to available RNASeq and Copy Number Variation data to select significant circadian genes associates with cancer progression. RESULTS Using a Bayesian shrinkage approach with the Bayesian accelerated failure time (AFT) model we showed the circadian clock associated gene DEC1 is positively correlated to survival outcome in breast cancer patients. The R package circgene implementing the methodology is available at https://github.com/MAITYA02/circgene. CONCLUSIONS The proposed Bayesian hierarchical model is the first shrinkage prior based model in its kind which integrates two omics platforms to identify the significant circadian gene for cancer survival.
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Affiliation(s)
- Arnab Kumar Maity
- Early Clinical Development Oncology Statistics, Pfizer Inc., 10777 Science Center Drive, 92121 San Diego, USA
| | - Sang Chan Lee
- Department of Statistics, Texas A&M University, 3143 TAMU, 77843 College Station, USA
| | - Linhan Hu
- Department of Statistics, Texas A&M University, 3143 TAMU, 77843 College Station, USA
| | | | - Bani K. Mallick
- Department of Statistics, Texas A&M University, 3143 TAMU, 77843 College Station, USA
| | - Tapasree Roy Sarkar
- Department of Statistics, Texas A&M University, 3143 TAMU, 77843 College Station, USA
- Department of Biology, Texas A&M University, 3258 TAMU, 77843 College Station, USA
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5
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Alder-Rangel A, Idnurm A, Brand AC, Brown AJP, Gorbushina A, Kelliher CM, Campos CB, Levin DE, Bell-Pedersen D, Dadachova E, Bauer FF, Gadd GM, Braus GH, Braga GUL, Brancini GTP, Walker GM, Druzhinina I, Pócsi I, Dijksterhuis J, Aguirre J, Hallsworth JE, Schumacher J, Wong KH, Selbmann L, Corrochano LM, Kupiec M, Momany M, Molin M, Requena N, Yarden O, Cordero RJB, Fischer R, Pascon RC, Mancinelli RL, Emri T, Basso TO, Rangel DEN. The Third International Symposium on Fungal Stress - ISFUS. Fungal Biol 2020; 124:235-252. [PMID: 32389286 DOI: 10.1016/j.funbio.2020.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 02/11/2020] [Indexed: 12/19/2022]
Abstract
Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in São José dos Campos, São Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.
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Affiliation(s)
| | - Alexander Idnurm
- School of BioSciences, The University of Melbourne, VIC, Australia
| | - Alexandra C Brand
- Medical Research Council Centre for Medical Mycology at the University of Exeter, Exeter, England, UK
| | - Alistair J P Brown
- Medical Research Council Centre for Medical Mycology at the University of Exeter, Exeter, England, UK
| | - Anna Gorbushina
- Bundesanstalt für Materialforschung und -prüfung, Materials and the Environment, Berlin, Germany
| | - Christina M Kelliher
- Department of Molecular & Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Claudia B Campos
- Departamento de Ciência e Tecnologia, Universidade Federal de São Paulo, São José dos Campos, SP, Brazil
| | - David E Levin
- Boston University Goldman School of Dental Medicine, Boston, MA, USA
| | - Deborah Bell-Pedersen
- Center for Biological Clocks Research, Department of Biology, Texas A&M University, College Station, TX, USA
| | - Ekaterina Dadachova
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
| | - Florian F Bauer
- Institute for Wine Biotechnology, Department of Viticulture and Oenology, Stellenbosch University, Matieland, South Africa
| | - Geoffrey M Gadd
- Geomicrobiology Group, School of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Gerhard H Braus
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Goettingen Center for Molecular Biosciences, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Gilberto U L Braga
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Guilherme T P Brancini
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Graeme M Walker
- School of Applied Sciences, Abertay University, Dundee, Scotland, UK
| | | | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Jan Dijksterhuis
- Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands
| | - Jesús Aguirre
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - John E Hallsworth
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK
| | - Julia Schumacher
- Bundesanstalt für Materialforschung und -prüfung, Materials and the Environment, Berlin, Germany
| | - Koon Ho Wong
- Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau SAR, China
| | - Laura Selbmann
- Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, Italy; Italian National Antarctic Museum (MNA), Mycological Section, Genoa, Italy
| | | | - Martin Kupiec
- School of Molecular Cell Biology and Biotechnology, Tel Aviv University, Tel Aviv, Israel
| | - Michelle Momany
- Fungal Biology Group & Plant Biology Department, University of Georgia, Athens, GA, USA
| | - Mikael Molin
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Natalia Requena
- Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Oded Yarden
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jeruslaem, Rehovot 7610001, Israel
| | - Radamés J B Cordero
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Reinhard Fischer
- Department of Microbiology, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Renata C Pascon
- Biological Sciences Department, Universidade Federal de São Paulo, Diadema, SP, Brazil
| | | | - Tamas Emri
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Thiago O Basso
- Department of Chemical Engineering, Escola Politécnica, Universidade de São Paulo, São Paulo, SP, Brazil
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Wu C, Dasgupta A, Shen L, Bell-Pedersen D, Sachs MS. The cell free protein synthesis system from the model filamentous fungus Neurospora crassa. Methods 2018; 137:11-19. [PMID: 29294368 PMCID: PMC6047757 DOI: 10.1016/j.ymeth.2017.12.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 12/06/2017] [Indexed: 11/23/2022] Open
Abstract
Cell-free protein synthesis (CFPS) can be used in many applications to produce polypeptides and to analyze mechanisms of mRNA translation. Here we describe how to make and use a CPFS system from the model filamentous fungus Neurospora crassa. The extensive genetic resources available in this system provide capacities to exploit robust CFPS for understanding translational control. Included are procedures for the growth and harvesting of cells, the preparation of cell-free extracts that serve as the source of the translational machinery in the CFPS and the preparation of synthetic mRNA to program the CFPS. Methods to accomplish cell-free translation and analyze protein synthesis, and to map positions of ribosomes on mRNAs by toeprinting, are described.
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Affiliation(s)
- Cheng Wu
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Ananya Dasgupta
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Lunda Shen
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | | | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
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7
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Goldsmith CS, Kim SM, Karunarathna N, Neuendorff N, Toussaint LG, Earnest DJ, Bell-Pedersen D. Inhibition of p38 MAPK activity leads to cell type-specific effects on the molecular circadian clock and time-dependent reduction of glioma cell invasiveness. BMC Cancer 2018; 18:43. [PMID: 29316898 PMCID: PMC5761097 DOI: 10.1186/s12885-017-3896-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 12/08/2017] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND The circadian clock is the basis for biological time keeping in eukaryotic organisms. The clock mechanism relies on biochemical signaling pathways to detect environmental stimuli and to regulate the expression of clock-controlled genes throughout the body. MAPK signaling pathways function in both circadian input and output pathways in mammals depending on the tissue; however, little is known about the role of p38 MAPK, an established tumor suppressor, in the mammalian circadian system. Increased expression and activity of p38 MAPK is correlated with poor prognosis in cancer, including glioblastoma multiforme; however, the toxicity of p38 MAPK inhibitors limits their clinical use. Here, we test if timed application of the specific p38 MAPK inhibitor VX-745 reduces glioma cell invasive properties in vitro. METHODS The levels and rhythmic accumulation of active phosphorylated p38 MAPK in different cell lines were determined by western blots. Rhythmic luciferase activity from clock gene luciferase reporter cells lines was used to test the effect of p38 MAPK inhibition on clock properties as determined using the damped sine fit and Levenberg-Marquardt algorithm. Nonlinear regression and Akaike's information criteria were used to establish rhythmicity. Boyden chamber assays were used to measure glioma cell invasiveness following time-of-day-specific treatment with VX-745. Significant differences were established using t-tests. RESULTS We demonstrate the activity of p38 MAPK cycles under control of the clock in mouse fibroblast and SCN cell lines. The levels of phosphorylated p38 MAPK were significantly reduced in clock-deficient cells, indicating that the circadian clock plays an important role in activation of this pathway. Inhibition of p38 MAPK activity with VX-745 led to cell-type-specific period changes in the molecular clock. In addition, phosphorylated p38 MAPK levels were rhythmic in HA glial cells, and high and arrhythmic in invasive IM3 glioma cells. We show that inhibition of p38 MAPK activity in IM3 cells at the time of day when the levels are normally low in HA cells under control of the circadian clock, significantly reduced IM3 invasiveness. CONCLUSIONS Glioma treatment with p38 MAPK inhibitors may be more effective and less toxic if administered at the appropriate time of the day.
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Affiliation(s)
- Charles S Goldsmith
- Interdisciplinary Program in Genetics, Texas A&M University, College Station TX, Texas, 77843, USA
| | - Sam Moon Kim
- Department of Biology, Texas A&M University, College Station, Texas, TX, 77843, USA
| | - Nirmala Karunarathna
- Department of Biology, Texas A&M University, College Station, Texas, TX, 77843, USA
| | - Nichole Neuendorff
- Department of Neuroscience and Experimental Therapeutics, Texas A&M, Health Science Center, College of Medicine Bryan, Texas, TX, 77807-3260, USA
| | - L Gerard Toussaint
- Department of Neuroscience and Experimental Therapeutics, Texas A&M, Health Science Center, College of Medicine Bryan, Texas, TX, 77807-3260, USA
| | - David J Earnest
- Department of Biology, Texas A&M University, College Station, Texas, TX, 77843, USA. .,Department of Neuroscience and Experimental Therapeutics, Texas A&M, Health Science Center, College of Medicine Bryan, Texas, TX, 77807-3260, USA. .,Center for Biological Clocks Research, Texas A&M University, College Station, Texas, TX, 77843, USA. .,Interdisciplinary Program in Neuroscience, Texas A&M University, College Station, Texas, TX, 77843, USA.
| | - Deborah Bell-Pedersen
- Interdisciplinary Program in Genetics, Texas A&M University, College Station TX, Texas, 77843, USA. .,Department of Biology, Texas A&M University, College Station, Texas, TX, 77843, USA. .,Center for Biological Clocks Research, Texas A&M University, College Station, Texas, TX, 77843, USA.
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8
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Hughes ME, Abruzzi KC, Allada R, Anafi R, Arpat AB, Asher G, Baldi P, de Bekker C, Bell-Pedersen D, Blau J, Brown S, Ceriani MF, Chen Z, Chiu JC, Cox J, Crowell AM, DeBruyne JP, Dijk DJ, DiTacchio L, Doyle FJ, Duffield GE, Dunlap JC, Eckel-Mahan K, Esser KA, FitzGerald GA, Forger DB, Francey LJ, Fu YH, Gachon F, Gatfield D, de Goede P, Golden SS, Green C, Harer J, Harmer S, Haspel J, Hastings MH, Herzel H, Herzog ED, Hoffmann C, Hong C, Hughey JJ, Hurley JM, de la Iglesia HO, Johnson C, Kay SA, Koike N, Kornacker K, Kramer A, Lamia K, Leise T, Lewis SA, Li J, Li X, Liu AC, Loros JJ, Martino TA, Menet JS, Merrow M, Millar AJ, Mockler T, Naef F, Nagoshi E, Nitabach MN, Olmedo M, Nusinow DA, Ptáček LJ, Rand D, Reddy AB, Robles MS, Roenneberg T, Rosbash M, Ruben MD, Rund SSC, Sancar A, Sassone-Corsi P, Sehgal A, Sherrill-Mix S, Skene DJ, Storch KF, Takahashi JS, Ueda HR, Wang H, Weitz C, Westermark PO, Wijnen H, Xu Y, Wu G, Yoo SH, Young M, Zhang EE, Zielinski T, Hogenesch JB. Guidelines for Genome-Scale Analysis of Biological Rhythms. J Biol Rhythms 2017; 32:380-393. [PMID: 29098954 PMCID: PMC5692188 DOI: 10.1177/0748730417728663] [Citation(s) in RCA: 155] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Genome biology approaches have made enormous contributions to our understanding of biological rhythms, particularly in identifying outputs of the clock, including RNAs, proteins, and metabolites, whose abundance oscillates throughout the day. These methods hold significant promise for future discovery, particularly when combined with computational modeling. However, genome-scale experiments are costly and laborious, yielding “big data” that are conceptually and statistically difficult to analyze. There is no obvious consensus regarding design or analysis. Here we discuss the relevant technical considerations to generate reproducible, statistically sound, and broadly useful genome-scale data. Rather than suggest a set of rigid rules, we aim to codify principles by which investigators, reviewers, and readers of the primary literature can evaluate the suitability of different experimental designs for measuring different aspects of biological rhythms. We introduce CircaInSilico, a web-based application for generating synthetic genome biology data to benchmark statistical methods for studying biological rhythms. Finally, we discuss several unmet analytical needs, including applications to clinical medicine, and suggest productive avenues to address them.
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Affiliation(s)
- Michael E Hughes
- 1 Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Katherine C Abruzzi
- 2 Department of Biology and Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts, USA
| | - Ravi Allada
- 3 Department of Neurobiology, Northwestern University, Evanston, Illinois, USA
| | - Ron Anafi
- 4 Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, USA
| | - Alaaddin Bulak Arpat
- 5 Center for Integrative Genomics, Génopode, University of Lausanne, Lausanne, Switzerland.,6 Vital-IT, Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Gad Asher
- 7 Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Pierre Baldi
- 8 Institute for Genomics and Bioinformatics, University of California, Irvine, USA
| | | | | | - Justin Blau
- 11 Department of Biology, New York University, New York, USA
| | - Steve Brown
- 12 Institute of Pharmacology and Toxicology, University of Zürich, Switzerland
| | - M Fernanda Ceriani
- 13 Laboratorio de Genética del Comportamiento, Fundación Instituto Leloir, IIBBA-CONICET, Buenos Aires, Argentina
| | - Zheng Chen
- 14 Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, USA
| | - Joanna C Chiu
- 15 Department of Entomology and Nematology, University of California, Davis, USA
| | - Juergen Cox
- 16 Computational Systems Biochemistry, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Alexander M Crowell
- 17 Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Jason P DeBruyne
- 18 Department of Pharmacology and Toxicology, Morehouse School of Medicine, Atlanta, Georgia, USA
| | - Derk-Jan Dijk
- 19 Surrey Sleep Research Centre, University of Surrey, Guildford, UK
| | - Luciano DiTacchio
- 20 The University of Kansas Medical Center, University of Kansas, Kansas City, USA
| | - Francis J Doyle
- 21 John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, USA
| | - Giles E Duffield
- 22 Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
| | - Jay C Dunlap
- 17 Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Kristin Eckel-Mahan
- 23 Institute of Molecular Medicine, McGovern Medical School, UT Health Houston, Houston, Texas, USA
| | - Karyn A Esser
- 24 Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, USA
| | - Garret A FitzGerald
- 25 Systems Pharmacology and Translational Therapeutics, University of Pennsylvania Perelman School of Medicine, Philadelphia, USA
| | - Daniel B Forger
- 26 Department of Mathematics, University of Michigan, Ann Arbor, USA
| | - Lauren J Francey
- 27 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Ying-Hui Fu
- 28 Kavli Institute for Fundamental Neuroscience, Weill Institute of Neuroscience, Department of Neurology, University of California, San Francisco, USA
| | - Frédéric Gachon
- 29 Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - David Gatfield
- 5 Center for Integrative Genomics, Génopode, University of Lausanne, Lausanne, Switzerland
| | - Paul de Goede
- 30 Department of Endocrinology & Metabolism, Academic Medical Center, Amsterdam, the Netherlands
| | - Susan S Golden
- 31 Center for Circadian Biology and Division of Biological Sciences, University of California, San Diego, La Jolla, USA
| | - Carla Green
- 32 Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, USA
| | - John Harer
- 33 Department of Mathematics, Duke University, Durham, North Carolina, USA
| | - Stacey Harmer
- 34 Department of Plant Biology, University of California, Davis, USA
| | - Jeff Haspel
- 1 Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael H Hastings
- 35 Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Hanspeter Herzel
- 36 Institute for Theoretical Biology, Charité-Universitätsmedizin Berlin, Germany
| | - Erik D Herzog
- 37 Department of Biology, Washington University in St. Louis, Missouri, USA
| | - Christy Hoffmann
- 1 Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Christian Hong
- 27 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Jacob J Hughey
- 38 Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Jennifer M Hurley
- 39 Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, USA
| | | | - Carl Johnson
- 41 Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Steve A Kay
- 42 Department of Cell and Molecular Biology, The Scripps Research Institute, University of California, San Diego, La Jolla, USA
| | - Nobuya Koike
- 43 Department of Physiology and Systems Bioscience, Kyoto Prefectural University of Medicine, Japan
| | - Karl Kornacker
- 44 Division of Sensory Biophysics, The Ohio State University, Columbus, USA
| | - Achim Kramer
- 45 Laboratory of Chronobiology, Charité Universitätsmedizin Berlin, Germany
| | - Katja Lamia
- 46 Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA
| | - Tanya Leise
- 47 Department of Mathematics and Statistics, Amherst College, Amherst, Massachusetts, USA
| | - Scott A Lewis
- 1 Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Jiajia Li
- 1 Division of Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.,48 Department of Biology, University of Missouri-St. Louis, USA
| | - Xiaodong Li
- 49 Department of Cell Biology, College of Life Sciences at Wuhan University, China
| | - Andrew C Liu
- 50 Department of Biological Sciences, University of Memphis, Tennessee, USA
| | - Jennifer J Loros
- 51 Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Tami A Martino
- 52 Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Jerome S Menet
- 10 Department of Biology, Texas A&M University, College Station, USA
| | - Martha Merrow
- 53 Institute of Medical Psychology, Faculty of Medicine, LMU Munich, Germany
| | - Andrew J Millar
- 54 SynthSys and School of Biological Sciences, University of Edinburgh, UK
| | - Todd Mockler
- 55 Donald Danforth Plant Science Center, St. Louis, Missouri, USA
| | - Felix Naef
- 56 The Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Switzerland
| | - Emi Nagoshi
- 57 Department of Genetics and Evolution, University of Geneva, Switzerland
| | - Michael N Nitabach
- 58 Department of Cellular and Molecular Physiology, Department of Genetics, Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, Connecticut, USA
| | - Maria Olmedo
- 59 Department of Genetics, University of Seville, Spain
| | - Dmitri A Nusinow
- 55 Donald Danforth Plant Science Center, St. Louis, Missouri, USA
| | - Louis J Ptáček
- 60 Department of Neurology, University of California, San Francisco, USA
| | - David Rand
- 61 Warwick Systems Biology and Mathematics Institute, University of Warwick, Conventry, UK
| | - Akhilesh B Reddy
- 62 The Francis Crick Institute, London, UK, and UCL Institute of Neurology, Queen Square, London, UK
| | - Maria S Robles
- 53 Institute of Medical Psychology, Faculty of Medicine, LMU Munich, Germany
| | - Till Roenneberg
- 53 Institute of Medical Psychology, Faculty of Medicine, LMU Munich, Germany
| | - Michael Rosbash
- 2 Department of Biology and Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts, USA
| | - Marc D Ruben
- 27 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Samuel S C Rund
- 63 Centre for Immunity, Infection and Evolution, University of Edinburgh, UK
| | - Aziz Sancar
- 64 Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, USA
| | - Paolo Sassone-Corsi
- 65 Department of Biological Chemistry, Center for Epigenetics and Metabolism, University of California, Irvine, USA
| | - Amita Sehgal
- 66 Howard Hughes Medical Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, USA
| | - Scott Sherrill-Mix
- 67 Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, USA
| | - Debra J Skene
- 68 Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Kai-Florian Storch
- 69 Department of Psychiatry, Douglas Mental Health University Institute, McGill University, Montreal, Canada
| | - Joseph S Takahashi
- 70 Howard Hughes Medical Institute, Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, USA
| | - Hiroki R Ueda
- 71 Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Laboratory for Synthetic Biology, RIKEN Quantitative Biology Center, Osaka, Japan
| | - Han Wang
- 72 Center for Circadian Clocks, Soochow University, Suzhou, Jiangsu, China
| | - Charles Weitz
- 73 Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Pål O Westermark
- 74 Institute of Genetics and Biometry, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Herman Wijnen
- 75 Biological Sciences and Institute for Life Sciences, University of Southampton, UK
| | - Ying Xu
- 76 Cam-Su GRC, Soochow University, Suzhou, China
| | - Gang Wu
- 27 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Seung-Hee Yoo
- 14 Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, USA
| | - Michael Young
- 77 Laboratory of Genetics, Rockefeller University, New York, New York, USA
| | | | - Tomasz Zielinski
- 54 SynthSys and School of Biological Sciences, University of Edinburgh, UK
| | - John B Hogenesch
- 27 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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9
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Dekhang R, Wu C, Smith KM, Lamb TM, Peterson M, Bredeweg EL, Ibarra O, Emerson JM, Karunarathna N, Lyubetskaya A, Azizi E, Hurley JM, Dunlap JC, Galagan JE, Freitag M, Sachs MS, Bell-Pedersen D. The Neurospora Transcription Factor ADV-1 Transduces Light Signals and Temporal Information to Control Rhythmic Expression of Genes Involved in Cell Fusion. G3 (Bethesda) 2017; 7:129-142. [PMID: 27856696 PMCID: PMC5217103 DOI: 10.1534/g3.116.034298] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/01/2016] [Indexed: 12/20/2022]
Abstract
Light and the circadian clock have a profound effect on the biology of organisms through the regulation of large sets of genes. Toward understanding how light and the circadian clock regulate gene expression, we used genome-wide approaches to identify the direct and indirect targets of the light-responsive and clock-controlled transcription factor ADV-1 in Neurospora crassa A large proportion of ADV-1 targets were found to be light- and/or clock-controlled, and enriched for genes involved in development, metabolism, cell growth, and cell fusion. We show that ADV-1 is necessary for transducing light and/or temporal information to its immediate downstream targets, including controlling rhythms in genes critical to somatic cell fusion. However, while ADV-1 targets are altered in predictable ways in Δadv-1 cells in response to light, this is not always the case for rhythmic target gene expression. These data suggest that a complex regulatory network downstream of ADV-1 functions to generate distinct temporal dynamics of target gene expression relative to the central clock mechanism.
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Affiliation(s)
- Rigzin Dekhang
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Cheng Wu
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Kristina M Smith
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Teresa M Lamb
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | | | - Erin L Bredeweg
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Oneida Ibarra
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Jillian M Emerson
- Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | | | | | - Elham Azizi
- Bioinformatics Program, Boston University, Massachusetts 02215
| | - Jennifer M Hurley
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Jay C Dunlap
- Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - James E Galagan
- Bioinformatics Program, Boston University, Massachusetts 02215
- National Emerging Infectious Diseases Laboratories, Boston University, Massachusetts 02118
- Department of Microbiology, Boston University, Massachusetts 02215
- Department of Biomedical Engineering, Boston University, Massachusetts 02215
| | - Michael Freitag
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Matthew S Sachs
- Department of Biology, Texas A&M University, College Station, Texas 77843
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10
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de Paula RM, Lewis ZA, Greene AV, Seo KS, Morgan LW, Vitalini MW, Bennett L, Gomer RH, Bell-Pedersen D. Two Circadian Timing Circuits in Neurospora crassa Cells Share Components and Regulate Distinct Rhythmic Processes. J Biol Rhythms 2016; 21:159-68. [PMID: 16731655 DOI: 10.1177/0748730406288338] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In Neurospora crassa, FRQ, WC-1, and WC-2 proteins comprise the core circadian FRQ-based oscillator that is directly responsive to light and drives daily rhythms in spore development and gene expression. However, physiological and biochemical studies have demonstrated the existence of additional oscillators in the cell that function in the absence of FRQ (collectively termed FRQ-less oscillators [FLOs]). Whether or not these represent temperature-compensated, entrainable circadian oscillators is not known. The authors previously identified an evening-peaking gene, W06H2 (now called clock-controlled gene 16 [ ccg-16]), which is expressed with a robust daily rhythm in cells that lack FRQ protein, suggesting that ccg-16 is regulated by a FLO. In this study, the authors provide evidence that the FLO driving ccg-16 rhythmicity is a circadian oscillator. They find that ccg-16 rhythms are generated by a temperature-responsive, temperature-compensated circadian FLO that, similar to the FRQ-based oscillator, requires functional WC-1 and WC-2 proteins for activity. They also find that FRQ is not essential for rhythmic WC-1 protein levels, raising the possibility that this WCFLO is involved in the generation of WC-1 rhythms. The results are consistent with the presence of 2 circadian oscillators within Neurospora cells, which the authors speculate may interact with each other through the shared WC proteins.
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Affiliation(s)
- Renato M de Paula
- Department of Biology, Center for Research on Biological Clocks, Texas A&M University, College Station, TX 77843, USA
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11
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Abstract
The mitogen-activated protein kinase (MAPK) family of genes aids cells in sensing both extracellular and intracellular stimuli, and emerging data indicate that MAPKs have fundamental, yet diverse, roles in the circadian biological clock. In the mammalian suprachiasmatic nucleus (SCN), MAPK pathways can function as inputs allowing the endogenous clock to entrain to 24h environmental cycles. MAPKs can also interact physically and/or genetically with components of the molecular circadian oscillator, implying that MAPKs can affect the cycling of the clock. Finally, circadian rhythms in MAPK pathway activation exist in many different tissue types and in model organisms, providing a mechanism to coordinately control the expression tissue-specific target genes at the proper time of day. As such, it should probably not come as a surprise that MAPK signaling pathways and circadian clocks affect similar biological processes and defects in either pathway lead to many of the same types of human diseases, highlighting the need to better define the mechanisms that link these two fundamental pathways together.
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12
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Abstract
This chapter describes our current understanding of the genetics of the Neurospora clock and summarizes the important findings in this area in the past decade. Neurospora is the most intensively studied clock system, and the reasons for this are listed. A discussion of the genetic interactions between clock mutants is included, highlighting the utility of dissecting complex mechanisms by genetic means. The molecular details of the Neurospora circadian clock mechanism are described, as well as the mutations that affect the key clock proteins, FRQ, WC-1, and WC-2, with an emphasis on the roles of protein phosphorylation. Studies on additional genes affecting clock properties are described and place these genes into two categories: those that affect the FRQ/WCC oscillator and those that do not. A discussion of temperature compensation and the mutants affecting this property is included. A section is devoted to the observations pertinent to the existence of other oscillators in this organism with respect to their properties, their effects, and their preliminary characterization. The output of the clock and the control of clock-controlled genes are discussed, emphasizing the phasing of these genes and the layers of control. In conclusion, the authors provide an outlook summarizing their suggestions for areas that would be fruitful for further exploration.
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13
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Bell-Pedersen D. Fungal photobiology. Introduction. Fungal Genet Biol 2010; 47:879-80. [PMID: 20619349 DOI: 10.1016/j.fgb.2010.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 07/01/2010] [Indexed: 11/28/2022]
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14
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15
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Abstract
Circadian clocks and mitogen-activated protein kinase (MAPK) signaling pathways are fundamental features of eukaryotic cells. Both pathways provide mechanisms for cells to respond to environmental stimuli, and links between them are known. We recently reported that the circadian clock in Neurospora crassa regulates daily rhythms in accumulation of phosphorylated, and thus active, OS-2 MAPK, a relative of mammalian p38 MAPK, when cells are grown in constant conditions. In the absence of acute stress, rhythmically activated MAPK then signals to downstream effector molecules to regulate rhythmic expression of target genes of the pathway. Clock regulation of MAPK signaling pathways provides a mechanism to coordinately control major groups of genes such that they peak at the appropriate times of day to provide a growth and survival advantage to the organism by anticipating stresses. MAPK pathways are well known for their role in cell proliferation and tumor suppression. New evidence reveals that some mammalian clock components also function as tumor suppressors and rhythms in phospho-MAPK have been observed in higher eukaryotes. Thus, the role of the clock in regulation of the activity of MAPK pathways provides important clues into the function of the circadian clock as a tumor suppressor.
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Affiliation(s)
- Renato M de Paula
- Center for Biological Clocks Research, Program for the Biology of Filamentous Fungi, and Department of Biology, Texas A&M University, Texas 77843, USA
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16
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Dunlap JC, Loros JJ, Aronson BD, Merrow M, Crosthwaite S, Bell-Pedersen D, Johnson K, Lindgren K, Garceau NY. The genetic basis of the circadian clock: identification of frq and FRQ as clock components in Neurospora. Ciba Found Symp 2007; 183:3-17; discussion 17-25. [PMID: 7656691 DOI: 10.1002/9780470514597.ch2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Genetic approaches to the identification of clock components have succeeded in two model systems, Neurospora and Drosophila. In each organism, genes identified through screens for clock-affecting mutations (frq in Neurospora, per in Drosophila) have subsequently been shown to have characteristics of central clock components: (1) mutations in each gene can affect period length and temperature compensation, two canonical characteristics of circadian systems; (2) each gene regulates the timing of its own transcription in a circadian manner; and (3) in the case of frq, constitutively elevated expression will set the phase of the clock on release into normal conditions. Despite clear genetic and molecular similarities, however, the two genes are neither molecular nor temporal homologues. The timing of peak expression is distinct in the two genes, frq expression peaking after dawn and per expression peaking near midnight. Also, although expression of per from a constitutive promoter can rescue rhythmicity in a fly lacking the gene, constitutive expression of frq will not rescue rhythmicity in Neurospora frq-null strains, and in fact causes arrhythmicity when expressed in a wild-type strain. These data suggest that frq is and/or encodes a state variable of the circadian oscillator. Recent molecular genetic analyses of frq have shed light on the origin of temperature compensation and strongly suggest that this property is built into the oscillatory feedback loop rather than appended to it. It seems plausible that clocks are adjusted and reset through adjustments in central clock components such as frq, and, by extension, per.
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Affiliation(s)
- J C Dunlap
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA
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17
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Affiliation(s)
- Yi Liu
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9040, USA.
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18
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Abstract
Research in Neurospora crassa pioneered the isolation of clock-controlled genes (ccgs), and more than 180 ccgs have been identified that function in various aspects of the fungal life cycle. Many clock-controlled genes are associated with damage repair, stress responses, intermediary metabolism, protein synthesis, and development. The expression of most of these genes peaks just before dawn and appears to prepare the cells for the desiccation, mutagenesis, and stress caused by sunlight. Progress on characterization of the output signaling pathways from the circadian oscillator mechanism to the ccgs is discussed. The authors also review evidence suggesting that, similar to other clock model organisms, a connection exists between the redox state of the cell and the Neurospora clock. The authors speculate that the clock system may sense not only light but also the redox potential of the cell through one of the PAS domains of the core clock components WC-1 or WC-2.
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Affiliation(s)
- Michael W Vitalini
- Center for Biological Clocks Research, Department of Biology, Texas A&M University, College Station, TX 77843, USA
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19
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de Paula RM, Vitalini MW, Gomer RH, Bell-Pedersen D. Complexity of the Neurospora crassa circadian clock system: multiple loops and oscillators. Cold Spring Harb Symp Quant Biol 2007; 72:345-351. [PMID: 18419292 DOI: 10.1101/sqb.2007.72.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Organisms from bacteria to humans use a circadian clock to control daily biochemical, physiological, and behavioral rhythms. We review evidence from Neurospora crassa that suggests that the circadian clock is organized as a network of genes and proteins that form coupled evening- and morning-specific oscillatory loops that can function autonomously, respond differently to environmental inputs, and regulate phase-specific outputs. There is also evidence for coupled morning and evening oscillator loops in plants, insects, and mammals, suggesting conservation of clock organization. From a systems perspective, fungi provide a powerful model organism for investigating oscillator complexity, communication between oscillators, and addressing reasons why the system has evolved to be so complex.
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Affiliation(s)
- R M de Paula
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA
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20
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Galagan JE, Calvo SE, Cuomo C, Ma LJ, Wortman JR, Batzoglou S, Lee SI, Baştürkmen M, Spevak CC, Clutterbuck J, Kapitonov V, Jurka J, Scazzocchio C, Farman M, Butler J, Purcell S, Harris S, Braus GH, Draht O, Busch S, D'Enfert C, Bouchier C, Goldman GH, Bell-Pedersen D, Griffiths-Jones S, Doonan JH, Yu J, Vienken K, Pain A, Freitag M, Selker EU, Archer DB, Peñalva MA, Oakley BR, Momany M, Tanaka T, Kumagai T, Asai K, Machida M, Nierman WC, Denning DW, Caddick M, Hynes M, Paoletti M, Fischer R, Miller B, Dyer P, Sachs MS, Osmani SA, Birren BW. Sequencing of Aspergillus nidulans and comparative analysis with A. fumigatus and A. oryzae. Nature 2005; 438:1105-15. [PMID: 16372000 DOI: 10.1038/nature04341] [Citation(s) in RCA: 930] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 10/19/2005] [Indexed: 11/08/2022]
Abstract
The aspergilli comprise a diverse group of filamentous fungi spanning over 200 million years of evolution. Here we report the genome sequence of the model organism Aspergillus nidulans, and a comparative study with Aspergillus fumigatus, a serious human pathogen, and Aspergillus oryzae, used in the production of sake, miso and soy sauce. Our analysis of genome structure provided a quantitative evaluation of forces driving long-term eukaryotic genome evolution. It also led to an experimentally validated model of mating-type locus evolution, suggesting the potential for sexual reproduction in A. fumigatus and A. oryzae. Our analysis of sequence conservation revealed over 5,000 non-coding regions actively conserved across all three species. Within these regions, we identified potential functional elements including a previously uncharacterized TPP riboswitch and motifs suggesting regulation in filamentous fungi by Puf family genes. We further obtained comparative and experimental evidence indicating widespread translational regulation by upstream open reading frames. These results enhance our understanding of these widely studied fungi as well as provide new insight into eukaryotic genome evolution and gene regulation.
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Affiliation(s)
- James E Galagan
- The Broad Institute of MIT and Harvard, 320 Charles Street, Cambridge, Massachusetts 02142, USA
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21
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Bell-Pedersen D, Cassone VM, Earnest DJ, Golden SS, Hardin PE, Thomas TL, Zoran MJ. Circadian rhythms from multiple oscillators: lessons from diverse organisms. Nat Rev Genet 2005; 6:544-56. [PMID: 15951747 PMCID: PMC2735866 DOI: 10.1038/nrg1633] [Citation(s) in RCA: 941] [Impact Index Per Article: 49.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The organization of biological activities into daily cycles is universal in organisms as diverse as cyanobacteria, fungi, algae, plants, flies, birds and man. Comparisons of circadian clocks in unicellular and multicellular organisms using molecular genetics and genomics have provided new insights into the mechanisms and complexity of clock systems. Whereas unicellular organisms require stand-alone clocks that can generate 24-hour rhythms for diverse processes, organisms with differentiated tissues can partition clock function to generate and coordinate different rhythms. In both cases, the temporal coordination of a multi-oscillator system is essential for producing robust circadian rhythms of gene expression and biological activity.
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Affiliation(s)
- Deborah Bell-Pedersen
- Center for Research on Biological Clocks, Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA.
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22
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Xie X, Wilkinson HH, Correa A, Lewis ZA, Bell-Pedersen D, Ebbole DJ. Transcriptional response to glucose starvation and functional analysis of a glucose transporter of Neurospora crassa. Fungal Genet Biol 2005; 41:1104-19. [PMID: 15531214 DOI: 10.1016/j.fgb.2004.08.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2004] [Accepted: 08/27/2004] [Indexed: 11/30/2022]
Abstract
The response to glucose availability in Neurospora crassa was characterized by measuring transcript levels of 1335 genes represented on a cDNA microarray. We found that 19% of the 1335 genes were regulated at least twofold in response to glucose deprivation. Several sugar transporter homologs were found to be regulated by glucose. Functional analysis of one of these, hgt-1, indicates that it encodes a high-affinity glucose transporter. Comparing N. crassa profiling data with the published diauxic shift data from Saccharomyces cerevisiae revealed that the two fungi share similar, but not identical, transcriptional response patterns. Regulation of transcript levels measured by microarray analysis is consistent with previous measurements of central metabolism enzyme activities for N. crassa. Transcripts of genes for ethanol fermentation and the tricarboxylic acid cycle are abundant in glucose-rich medium, consistent with N. crassa carrying out a high rate of both fermentation and respiration simultaneously.
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Affiliation(s)
- Xin Xie
- Program for the Biology of Filamentous Fungi, Department of Plant Pathology and Microbiology, Texas A & M University, College Station, TX 77843, USA
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23
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Pregueiro AM, Price-Lloyd N, Bell-Pedersen D, Heintzen C, Loros JJ, Dunlap JC. Assignment of an essential role for the Neurospora frequency gene in circadian entrainment to temperature cycles. Proc Natl Acad Sci U S A 2005; 102:2210-5. [PMID: 15677317 PMCID: PMC548525 DOI: 10.1073/pnas.0406506102] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Circadian systems include slave oscillators and central pacemakers, and the cores of eukaryotic circadian clocks described to date are composed of transcription and translation feedback loops (TTFLs). In the model system Neurospora, normal circadian rhythmicity requires a TTFL in which a White Collar complex (WCC) activates expression of the frequency (frq) gene, and the FRQ protein feeds back to attenuate that activation. To further test the centrality of this TTFL to the circadian mechanism in Neurospora, we used low-amplitude temperature cycles to compare WT and frq-null strains under conditions in which a banding rhythm was elicited. WT cultures were entrained to these temperature cycles. Unlike those normal strains, however, frq-null mutants did not truly entrain to the same cycles. Their peaks and troughs always occurred in the cold and warm periods, respectively, strongly suggesting that the rhythm in Neurospora lacking frq function simply is driven by the temperature cycles. Previous reports suggested that a FRQ-less oscillator (FLO) could be entrained to temperature cycles, rather than being driven, and speculated that the FLO was the underlying circadian-rhythm generator. These inferences appear to derive from the use of a phase reference point affected by both the changing waveform and the phase of the oscillation. Examination of several other phase markers as well as results of additional experimental tests indicate that the FLO is, at best, a slave oscillator to the TTFL, which underlies circadian rhythm generation in Neurospora.
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Abstract
In most organisms, circadian oscillators regulate the daily rhythmic expression of clock-controlled genes (ccgs). However, little is known about the pathways between the circadian oscillator(s) and the ccgs. In Neurospora crassa, the frq, wc-1, and wc-2 genes encode components of the frq-oscillator. A functional frq-oscillator is required for rhythmic expression of the morning-specific ccg-1 and ccg-2 genes. In frq-null or wc-1 mutant strains, ccg-1 mRNA levels fluctuate near peak levels over the course of the day, whereas ccg-2 mRNA remains at trough levels. The simplest model that fits the above observations is that the frq-oscillator regulates a repressor of ccg-1 and an activator of ccg-2. We utilized a genetic selection for mutations that affect the regulation of ccg-1 and ccg-2 by the frq-oscillator. We find that there is at least one mutant strain, COP1-1 (circadian output pathway derived from ccg-1), that has altered expression of ccg-1 mRNA, but normal ccg-2 expression levels. However, the clock does not appear to simply regulate a repressor of ccg-1 and an activator of ccg-2 in two independent pathways, since in our selection we identified three mutant strains, COP1-2, COP1-3, and COP1-4, in which a single mutation in each strain affects the expression levels and rhythmicity of both ccg-1 and ccg-2.
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Affiliation(s)
- Michael W Vitalini
- Center for Biological Clocks Research and Program for the Biology of Filamentous Fungi, Department of Biology, Texas A&M University, College Station, Texas 77843, USA
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Allen GC, Farnell Y, Bell-Pedersen D, Cassone VM, Earnest DJ. Effects of altered Clock gene expression on the pacemaker properties of SCN2.2 cells and oscillatory properties of NIH/3T3 cells. Neuroscience 2004; 127:989-99. [PMID: 15312911 DOI: 10.1016/j.neuroscience.2004.06.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2004] [Indexed: 01/08/2023]
Abstract
While peripheral tissues and serum-shocked fibroblasts express rhythmic oscillations in clock gene expression, only the suprachiasmatic nucleus (SCN) is capable of endogenous, self-sustained rhythmicity and of functioning as a pacemaker by imposing rhythmic properties upon other cells. To differentially examine the molecular elements necessary for the distinctive rhythm-generating and pacemaking properties of the SCN, the effects of antisense inhibition of Clock expression on the rhythms in 2-deoxyglucose uptake and Per gene expression were compared in immortalized SCN cells and a fibroblast cell line. Similar to changes in molecular and physiological rhythmicity observed in the SCN of Clock mutant mice, the rhythmic pattern of Per2 expression was disrupted and the period of metabolic rhythmicity was increased in SCN2.2 cells subjected to antisense inhibition of Clock. NIH/3T3 fibroblasts cocultured with antisense-treated SCN2.2 cells showed metabolic rhythms with comparable increases in period and decreases in rhythm amplitude. Per2 expression in these cocultured fibroblasts exhibited a similar reduction in peak levels, but was marked by non-24 h or irregular peak-to-peak intervals. In serum-shocked NIH/3T3 fibroblasts, oscillations in Per2, Bmal1, and Cry1 expression persisted with some change in rhythm amplitude during antisense inhibition of CLOCK, demonstrating that feedback interactions between Clock and other core components of the clock mechanism may be regulated differently in SCN2.2 cells and fibroblasts. The present results suggest that CLOCK is differentially involved in the generation of endogenous molecular and metabolic rhythmicity within SCN2.2 cells and in the regulation of their specific outputs that control rhythmic processes in NIH/3T3 cells.
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Affiliation(s)
- G C Allen
- Department of Human Anatomy and Medical Neurobiology, Texas A&M University Health Science Center, College of Medicine, College Station, TX 77843-1114, USA
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Borkovich KA, Alex LA, Yarden O, Freitag M, Turner GE, Read ND, Seiler S, Bell-Pedersen D, Paietta J, Plesofsky N, Plamann M, Goodrich-Tanrikulu M, Schulte U, Mannhaupt G, Nargang FE, Radford A, Selitrennikoff C, Galagan JE, Dunlap JC, Loros JJ, Catcheside D, Inoue H, Aramayo R, Polymenis M, Selker EU, Sachs MS, Marzluf GA, Paulsen I, Davis R, Ebbole DJ, Zelter A, Kalkman ER, O'Rourke R, Bowring F, Yeadon J, Ishii C, Suzuki K, Sakai W, Pratt R. Lessons from the genome sequence of Neurospora crassa: tracing the path from genomic blueprint to multicellular organism. Microbiol Mol Biol Rev 2004; 68:1-108. [PMID: 15007097 PMCID: PMC362109 DOI: 10.1128/mmbr.68.1.1-108.2004] [Citation(s) in RCA: 434] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We present an analysis of over 1,100 of the approximately 10,000 predicted proteins encoded by the genome sequence of the filamentous fungus Neurospora crassa. Seven major areas of Neurospora genomics and biology are covered. First, the basic features of the genome, including the automated assembly, gene calls, and global gene analyses are summarized. The second section covers components of the centromere and kinetochore complexes, chromatin assembly and modification, and transcription and translation initiation factors. The third area discusses genome defense mechanisms, including repeat induced point mutation, quelling and meiotic silencing, and DNA repair and recombination. In the fourth section, topics relevant to metabolism and transport include extracellular digestion; membrane transporters; aspects of carbon, sulfur, nitrogen, and lipid metabolism; the mitochondrion and energy metabolism; the proteasome; and protein glycosylation, secretion, and endocytosis. Environmental sensing is the focus of the fifth section with a treatment of two-component systems; GTP-binding proteins; mitogen-activated protein, p21-activated, and germinal center kinases; calcium signaling; protein phosphatases; photobiology; circadian rhythms; and heat shock and stress responses. The sixth area of analysis is growth and development; it encompasses cell wall synthesis, proteins important for hyphal polarity, cytoskeletal components, the cyclin/cyclin-dependent kinase machinery, macroconidiation, meiosis, and the sexual cycle. The seventh section covers topics relevant to animal and plant pathogenesis and human disease. The results demonstrate that a large proportion of Neurospora genes do not have homologues in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. The group of unshared genes includes potential new targets for antifungals as well as loci implicated in human and plant physiology and disease.
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Affiliation(s)
- Katherine A Borkovich
- Department of Plant Pathology, University of California, Riverside, California 92521, USA. Katherine/
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Correa A, Lewis ZA, Greene AV, March IJ, Gomer RH, Bell-Pedersen D. Multiple oscillators regulate circadian gene expression in Neurospora. Proc Natl Acad Sci U S A 2003; 100:13597-602. [PMID: 14597725 PMCID: PMC263859 DOI: 10.1073/pnas.2233734100] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High-density microarrays were used to profile circadian gene expression in Neurospora crassa cultures grown in constant darkness. We identified 145 clock-controlled genes (ccgs). The ccgs peaked in mRNA accumulation at all phases of the day, with the majority peaking in the late night to early morning. The predicted or known functions of the ccgs demonstrate that the clock contributes to a wide range of cellular processes, including cell signaling, development, metabolism, and stress responses. Although the period of rhythm of most of the ccgs was found to depend on the well characterized frequency (FRQ)-based oscillator, three ccgs appeared to have a rhythm that was significantly short in the long period (29-h) frq7 mutant strain. These ccgs accumulate mRNA rhythmically with a circadian period in a frq-null strain, confirming the existence of a second oscillator in N. crassa.
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Affiliation(s)
- Alejandro Correa
- Center for Biological Clocks Research, Department of Biology, Texas A&M University, College Station, TX 77843, USA
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28
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Bailey MJ, Beremand PD, Hammer R, Bell-Pedersen D, Thomas TL, Cassone VM. Transcriptional profiling of the chick pineal gland, a photoreceptive circadian oscillator and pacemaker. Mol Endocrinol 2003; 17:2084-95. [PMID: 12881511 DOI: 10.1210/me.2003-0121] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The avian pineal gland contains both circadian oscillators and photoreceptors to produce rhythms in biosynthesis of the hormone melatonin in vivo and in vitro. The molecular mechanisms for melatonin biosynthesis are largely understood, but the mechanisms driving the rhythm itself or the photoreceptive processes that entrain the rhythm are unknown. We have produced cDNA microarrays of pineal gland transcripts under light-dark and constant darkness conditions. Rhythmic transcripts were classified according to function, representing diverse functional groups, including phototransduction pathways, transcription/translation factors, ion channel proteins, cell signaling molecules, and immune function genes. These were also organized relative to time of day mRNA abundance in light-dark and constant darkness. The transcriptional profile of the chick pineal gland reveals a more complex form of gene regulation than one might expect from a gland whose sole apparent function is the rhythmic biosynthesis of melatonin. The mRNAs encoding melatonin biosynthesis are rhythmic as are many orthologs of mammalian "clock genes." However, the oscillation of phototransductive, immune, stress response, hormone binding, and other important processes in the transcriptome of the pineal gland, raises new questions regarding the role of the pineal gland in circadian rhythm generation, organization, and avian physiology.
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Affiliation(s)
- Michael J Bailey
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA
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29
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Galagan JE, Calvo SE, Borkovich KA, Selker EU, Read ND, Jaffe D, FitzHugh W, Ma LJ, Smirnov S, Purcell S, Rehman B, Elkins T, Engels R, Wang S, Nielsen CB, Butler J, Endrizzi M, Qui D, Ianakiev P, Bell-Pedersen D, Nelson MA, Werner-Washburne M, Selitrennikoff CP, Kinsey JA, Braun EL, Zelter A, Schulte U, Kothe GO, Jedd G, Mewes W, Staben C, Marcotte E, Greenberg D, Roy A, Foley K, Naylor J, Stange-Thomann N, Barrett R, Gnerre S, Kamal M, Kamvysselis M, Mauceli E, Bielke C, Rudd S, Frishman D, Krystofova S, Rasmussen C, Metzenberg RL, Perkins DD, Kroken S, Cogoni C, Macino G, Catcheside D, Li W, Pratt RJ, Osmani SA, DeSouza CPC, Glass L, Orbach MJ, Berglund JA, Voelker R, Yarden O, Plamann M, Seiler S, Dunlap J, Radford A, Aramayo R, Natvig DO, Alex LA, Mannhaupt G, Ebbole DJ, Freitag M, Paulsen I, Sachs MS, Lander ES, Nusbaum C, Birren B. The genome sequence of the filamentous fungus Neurospora crassa. Nature 2003; 422:859-68. [PMID: 12712197 DOI: 10.1038/nature01554] [Citation(s) in RCA: 1129] [Impact Index Per Article: 53.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Accepted: 03/14/2003] [Indexed: 11/09/2022]
Abstract
Neurospora crassa is a central organism in the history of twentieth-century genetics, biochemistry and molecular biology. Here, we report a high-quality draft sequence of the N. crassa genome. The approximately 40-megabase genome encodes about 10,000 protein-coding genes--more than twice as many as in the fission yeast Schizosaccharomyces pombe and only about 25% fewer than in the fruitfly Drosophila melanogaster. Analysis of the gene set yields insights into unexpected aspects of Neurospora biology including the identification of genes potentially associated with red light photobiology, genes implicated in secondary metabolism, and important differences in Ca2+ signalling as compared with plants and animals. Neurospora possesses the widest array of genome defence mechanisms known for any eukaryotic organism, including a process unique to fungi called repeat-induced point mutation (RIP). Genome analysis suggests that RIP has had a profound impact on genome evolution, greatly slowing the creation of new genes through genomic duplication and resulting in a genome with an unusually low proportion of closely related genes.
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Affiliation(s)
- James E Galagan
- Whitehead Institute Center for Genome Research, 320 Charles Street, Cambridge, Massachusetts 02141, USA.
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Abstract
We have constructed a plasmid vector for expressing firefly luciferase in Neurospora crassa under control of the light- and clock-regulated ccg-2 (eas) promoter. The sequence of the luciferase gene in the vector has been modified to reflect the N. crassa codon bias. Both light-induced activity and circadian activity are demonstrated. Expression of luciferase in strains carrying mutant frequency alleles shows appropriate period length alterations. These data demonstrate that luciferase is a sensitive reporter of gene expression in N. crassa. Our results also show that the modified luciferase is expressed in Aspergillus nidulans.
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Affiliation(s)
- Louis W Morgan
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
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Greene AV, Keller N, Haas H, Bell-Pedersen D. A circadian oscillator in Aspergillus spp. regulates daily development and gene expression. Eukaryot Cell 2003; 2:231-7. [PMID: 12684372 PMCID: PMC154850 DOI: 10.1128/ec.2.2.231-237.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2002] [Accepted: 01/15/2003] [Indexed: 11/20/2022]
Abstract
We have established the presence of a circadian clock in Aspergillus flavus and Aspergillus nidulans by morphological and molecular assays, respectively. In A. flavus, the clock regulates an easily assayable rhythm in the development of sclerotia, which are large survival structures produced by many fungi. This developmental rhythm exhibits all of the principal clock properties. The rhythm is maintained in constant environmental conditions with a period of 33 h at 30 degrees C, it can be entrained by environmental signals, and it is temperature compensated. This endogenous 33-h period is one of the longest natural circadian rhythms reported for any organism, and this likely contributes to some unique responses of the clock to environmental signals. In A. nidulans, no obvious rhythms in development are apparent. However, a free running and entrainable rhythm in the accumulation of gpdA mRNA (encoding glyceraldehyde-3-phosphate dehydrogenase) is observed, suggesting the presence of a circadian clock in this species. We are unable to identify an Aspergillus ortholog of frequency, a gene required for normal circadian rhythmicity in Neurospora crassa. Together, our data indicate the existence of an Aspergillus circadian clock, which has properties that differ from that of the well-described clock of N. crassa.
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Affiliation(s)
- Andrew V Greene
- Program in Biological Clocks, Department of Biology. Program in the Biology of Filamentous Fungi, Texas A&M University, College Station, Texas 77843, USA
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Bobrowicz P, Pawlak R, Correa A, Bell-Pedersen D, Ebbole DJ. The Neurospora crassa pheromone precursor genes are regulated by the mating type locus and the circadian clock. Mol Microbiol 2002; 45:795-804. [PMID: 12139624 DOI: 10.1046/j.1365-2958.2002.03052.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pheromones play important roles in female and male behaviour in the filamentous ascomycete fungi. To begin to explore the role of pheromones in mating, we have identified the genes encoding the sex pheromones of the heterothallic species Neurospora crassa. One gene, expressed exclusively in mat A strains, encodes a polypeptide containing multiple repeats of a putative pheromone sequence bordered by Kex2 processing sites. Strains of the opposite mating type, mat a, express a pheromone precursor gene whose polypeptide contains a C-terminal CAAX motif predicted to produce a mature pheromone with a C-terminal carboxy-methyl isoprenylated cysteine. The predicted sequences of the pheromones are remarkably similar to those encoded by other filamentous ascomycetes. The expression of the pheromone precursor genes is mating type specific and is under the control of the mating type locus. Furthermore, the genes are highly expressed in conidia and under conditions that favour sexual development. Both pheromone precursor genes are also regulated by the endogenous circadian clock in a time-of-day-specific fashion, supporting a role for the clock in mating.
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Affiliation(s)
- Piotr Bobrowicz
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843, USA
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Lewis ZA, Correa A, Schwerdtfeger C, Link KL, Xie X, Gomer RH, Thomas T, Ebbole DJ, Bell-Pedersen D. Overexpression of White Collar-1 (WC-1) activates circadian clock-associated genes, but is not sufficient to induce most light-regulated gene expression in Neurospora crassa. Mol Microbiol 2002; 45:917-31. [PMID: 12180913 DOI: 10.1046/j.1365-2958.2002.03074.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many processes in fungi are regulated by light, but the molecular mechanisms are not well understood. The White Collar-1 (WC-1) protein is required for all known blue-light responses in Neurospora crassa. In response to light, WC-1 levels increase, and the protein is transiently phosphorylated. To test the hypothesis that the increase in WC-1 levels after light treatment is sufficient to activate light-regulated gene expression, we used microarrays to identify genes that respond to light treatment. We then overexpressed WC-1 in dark-grown tissue and used the microarrays to identify genes regulated by an increase in WC-1 levels. We found that 3% of the genes were responsive to light, whereas 7% of the genes were responsive to WC-1 overexpression in the dark. However, only four out of 22 light-induced genes were also induced by WC-1 overexpression, demonstrating that changes in the levels of WC-1 are not sufficient to activate all light-responsive genes. The WC proteins are also required for circadian rhythms in dark-grown cultures and for light entrainment of the circadian clock, and WC-1 protein levels show a circadian rhythm in the dark. We found that representative samples of the mRNAs induced by over-expression of WC-1 show circadian fluctuations in their levels. These data suggest that WC-1 can mediate both light and circadian responses, with an increase in WC-1 levels affecting circadian clock-responsive gene regulation and other features of WC-1, possibly its phosphorylation, affecting light-responsive gene regulation.
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Affiliation(s)
- Z A Lewis
- Program in Biological Clocks, Department of Biology, Texas A & M University, College Station, TX 77843, USA
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Correa A, Bell-Pedersen D. Distinct signaling pathways from the circadian clock participate in regulation of rhythmic conidiospore development in Neurospora crassa. Eukaryot Cell 2002; 1:273-80. [PMID: 12455961 PMCID: PMC118037 DOI: 10.1128/ec.1.2.273-280.2002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Several different environmental signals can induce asexual spore development (conidiation) and expression of developmentally regulated genes in Neurospora crassa. However, under constant conditions, where no environmental cues for conidiation are present, the endogenous circadian clock in N. crassa promotes daily rhythms in expression of known developmental genes and of conidiation. We anticipated that the same pathway of gene regulation would be followed during clock-controlled conidiation and environmental induction of conidiation and that the circadian clock would need only to control the initial developmental switch. Previous experiments showed that high-level developmental induction of the clock-controlled genes eas (ccg-2) and ccg-1 requires the developmental regulatory proteins FL and ACON-2, respectively, and normal developmental induction of fl mRNA expression requires ACON-2. We demonstrate that the circadian clock regulates rhythmic fl gene expression and that fl rhythmicity requires ACON-2. However, we find that clock regulation of eas (ccg-2) is normal in an fl mutant strain and ccg-1 expression is rhythmic in an acon-2 mutant strain. Together, these data point to the endogenous clock and the environment following separate pathways to regulate conidiation-specific gene expression.
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Affiliation(s)
- Alejandro Correa
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA
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Shinohara ML, Correa A, Bell-Pedersen D, Dunlap JC, Loros JJ. Neurospora clock-controlled gene 9 (ccg-9) encodes trehalose synthase: circadian regulation of stress responses and development. Eukaryot Cell 2002; 1:33-43. [PMID: 12455969 PMCID: PMC118043 DOI: 10.1128/ec.1.1.33-43.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2001] [Accepted: 11/27/2001] [Indexed: 11/20/2022]
Abstract
The circadian clock of Neurospora crassa regulates the rhythmic expression of a number of genes encoding diverse functions which, as an ensemble, are adaptive to life in a rhythmic environment of alternating levels of light and dark, warmth and coolness, and dryness and humidity. Previous differential screens have identified a number of such genes based solely on their cycling expression, including clock-controlled gene 9 (ccg-9). Sequence analysis now shows the predicted CCG-9 polypeptide to be homologous to a novel form of trehalose synthase; as such it would catalyze the synthesis of the disaccharide trehalose, which plays an important role in protecting many cells from environmental stresses. Consistent with this, heat, glucose starvation, and osmotic stress induce ccg-9 transcript accumulation. Surprisingly, however, a parallel role in development is suggested by the finding that inactivation of ccg-9 results in altered conidiophore morphology and abolishes the normal circadian rhythm of asexual macroconidial development. Examination of a clock component, FRQ, in the ccg-9-null strain revealed normal cycling, phosphorylation, and light induction, indicating that loss of the conidiation rhythm is not due to changes in either the circadian oscillator or light input into the clock but pointing instead to a defect in circadian output. These data imply an interplay between a role of trehalose in stress protection and an apparent requirement for trehalose in clock regulation of conidiation under constant environmental conditions. This requirement can be bypassed by a daily light signal which drives a light-entrained rhythm in conidiation in the ccg-9-null strain; this bypass suggests that the trehalose requirement is related to clock control of development and not to the developmental process itself. Circadian control of trehalose synthase suggests a link between clock control of stress responses and that of development.
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Affiliation(s)
- Mari L Shinohara
- Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Morgan LW, Feldman JF, Bell-Pedersen D. Genetic interactions between clock mutations in Neurospora crassa: can they help us to understand complexity? Philos Trans R Soc Lond B Biol Sci 2001; 356:1717-24. [PMID: 11710978 PMCID: PMC1088547 DOI: 10.1098/rstb.2001.0967] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent work on circadian clocks in Neurospora has primarily focused on the frequency (frq) and white-collar (wc) loci. However, a number of other genes are known that affect either the period or temperature compensation of the rhythm. These include the period (no relationship to the period gene of Drosophila) genes and a number of genes that affect cellular metabolism. How these other loci fit into the circadian system is not known, and metabolic effects on the clock are typically not considered in single-oscillator models. Recent evidence has pointed to multiple oscillators in Neurospora, at least one of which is predicted to incorporate metabolic processes. Here, the Neurospora clock-affecting mutations will be reviewed and their genetic interactions discussed in the context of a more complex clock model involving two coupled oscillators: a FRQ/WC-based oscillator and a 'frq-less' oscillator that may involve metabolic components.
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Affiliation(s)
- L W Morgan
- Department of Biology, Texas A&M University, College Station, TX 77843-3248, USA
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Abstract
The fungus Neurospora crassa is being used by a number of research groups as a model organism to investigate circadian (daily) rhythmicity. In this review we concentrate on recent work relating to the complexity of the circadian system in this organism. We discuss: the advantages of Neurospora as a model system for clock studies; the frequency (frq), white collar-1 and white collar-2 genes and their roles in rhythmicity; the phenomenon of rhythmicity in null frq mutants and its implications for clock mechanisms; the study of output pathways using clock-controlled genes; other rhythms in fungi; mathematical modelling of the Neurospora circadian system; and the application of new technologies to the study of Neurospora rhythmicity. We conclude that there may be many gene products involved in the clock mechanism, there may be multiple interacting oscillators comprising the clock mechanism, there may be feedback from output pathways onto the oscillator(s) and from the oscillator(s) onto input pathways, and there may be several independent clocks coexisting in one organism. Thus even a relatively simple lower eukaryote can be used to address questions about a complex, networked circadian system.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
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38
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Bell-Pedersen D, Lewis ZA, Loros JJ, Dunlap JC. The Neurospora circadian clock regulates a transcription factor that controls rhythmic expression of the output eas(ccg-2) gene. Mol Microbiol 2001; 41:897-909. [PMID: 11532152 DOI: 10.1046/j.1365-2958.2001.02558.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The circadian clock provides a link between an organism's environment and its behaviour, temporally phasing the expression of genes in anticipation of daily environmental changes. Input pathways sense environmental information and interact with the clock to synchronize it to external cycles, and output pathways read out from the clock to impart temporal control on downstream targets. Very little is known about the regulation of outputs from the clock. In Neurospora crassa, the circadian clock transcriptionally regulates expression of the clock-controlled genes, including the well-characterized eas(ccg-2) gene. Dissection of the eas(ccg-2) gene promoter previously localized a 68 bp sequence containing an activating clock element (ACE) that is both necessary and sufficient for rhythmic activation of transcription by the circadian clock. Using electrophoretic mobility shift assays (EMSAs), we have identified light-regulated nuclear protein factors that bind specifically to the ACE in a time-of-day-dependent fashion, consistent with their role in circadian regulation of expression of eas(ccg-2). Nucleotides in the ACE that interact with the protein factors were determined using interference binding assays, and deletion of the core interacting sequences affected, but did not completely eliminate, rhythmic accumulation of eas(ccg-2) mRNA in vivo, whereas deletion of the entire ACE abolished the rhythm. These data indicate that redundant binding sites for the protein factors that promote eas(ccg-2) rhythms exist within the 68 bp ACE. The ACE binding complexes formed using protein extracts from cells with lesions in central components of the Neurospora circadian clock were identical to those formed with extracts from wild-type cells, indicating that other proteins directly control eas(ccg-2) rhythmic expression. These data suggest that the Neurospora crassa circadian clock regulates an unknown transcription factor, which in turn activates the expression of eas(ccg-2) at specific times of the day.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biology, Texas A & M University, College Station, TX 77843, USA.
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Shrode LB, Lewis ZA, White LD, Bell-Pedersen D, Ebbole DJ. vvd is required for light adaptation of conidiation-specific genes of Neurospora crassa, but not circadian conidiation. Fungal Genet Biol 2001; 32:169-81. [PMID: 11343403 DOI: 10.1006/fgbi.2001.1264] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
con-10 and con-6 are two of the conidiation (con) genes of Neurospora crassa that were identified based on their preferential expression during macroconidiophore development. They are also regulated by several other environmental stimuli independent of development, including a transient induction by light. We identified an allele of vivid (vvd) in a mutant screen designed to obtain strains with altered expression of con-10. vvd mutants display enhanced carotenoid pigmentation in response to light. In addition, con-10 and con-6 show a heightened response to photoinduction. We tested the function of the light-responsive circadian clock in the vvd mutant and found no major defect in the circadian rhythm of conidiation or light regulation of a key clock component, frequency (frq). We conclude that vvd is primarily involved in a process of light-dependent gene repression, called light adaptation. Although a number of gene products are known to control light induction in fungi, vvd is the first gene shown to have a role in adaptation to constant light.
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Affiliation(s)
- L B Shrode
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, 77843-2132, USA
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Zhu H, Nowrousian M, Kupfer D, Colot HV, Berrocal-Tito G, Lai H, Bell-Pedersen D, Roe BA, Loros JJ, Dunlap JC. Analysis of expressed sequence tags from two starvation, time-of-day-specific libraries of Neurospora crassa reveals novel clock-controlled genes. Genetics 2001; 157:1057-65. [PMID: 11238394 PMCID: PMC1461561 DOI: 10.1093/genetics/157.3.1057] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In an effort to determine genes that are expressed in mycelial cultures of Neurospora crassa over the course of the circadian day, we have sequenced 13,000 cDNA clones from two time-of-day-specific libraries (morning and evening library) generating approximately 20,000 sequences. Contig analysis allowed the identification of 445 unique expressed sequence tags (ESTs) and 986 ESTs present in multiple cDNA clones. For approximately 50% of the sequences (710 of 1431), significant matches to sequences in the National Center for Biotechnology Information database (of known or unknown function) were detected. About 50% of the ESTs (721 of 1431) showed no similarity to previously identified genes. We hybridized Northern blots with probes derived from 26 clones chosen from contigs identified by multiple cDNA clones and EST sequences. Using these sequences, the representation of genes among the morning and evening sequences, respectively, in most cases does not reflect their expression patterns over the course of the day. Nevertheless, we were able to identify four new clock-controlled genes. On the basis of these data we predict that a significant proportion of the expressed Neurospora genes may be regulated by the circadian clock. The mRNA levels of all four genes peak in the subjective morning as is the case with previously identified ccgs.
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Affiliation(s)
- H Zhu
- Department of Chemistry and Biochemistry, Advanced Center for Genome Technology, University of Oklahoma, Norman, Oklahoma 73019, USA
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Abstract
Circadian clocks have been described in organisms ranging in complexity from unicells to mammals, in which they function to control daily rhythms in cellular activities and behavior. The significance of a detailed understanding of the clock can be appreciated by its ubiquity and its established involvement in human physiology, including endocrine function, sleep/wake cycles, psychiatric illness, and drug tolerances and effectiveness. Because the clock in all organisms is assembled within the cell and clock mechanisms are evolutionarily conserved, simple eukaryotes provide appropriate experimental systems for dissecting the clock. Significant progress has been made in deciphering the circadian system in Neurospora crassa using both genetic and molecular approaches, and Neurospora has contributed greatly to our understanding of (1) the feedback cycle that comprises a circadian oscillator, (2) the mechanisms by which the clock is kept in synchrony with the environment, and (3) the genes that reside in rhythmic output pathways. Importantly, the lessons learned in Neurospora are relevant to our understanding of clocks in higher eukaryotes.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA
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Bell-Pedersen D, Shinohara ML, Loros JJ, Dunlap JC. Circadian clock-controlled genes isolated from Neurospora crassa are late night- to early morning-specific. Proc Natl Acad Sci U S A 1996; 93:13096-101. [PMID: 8917550 PMCID: PMC24052 DOI: 10.1073/pnas.93.23.13096] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/1996] [Accepted: 08/23/1996] [Indexed: 02/03/2023] Open
Abstract
An endogenous circadian biological clock controls the temporal aspects of life in most organisms, including rhythmic control of genes involved in clock output pathways. In the fungus Neurospora crassa, one pathway known to be under control of the clock is asexual spore (conidia) development. To understand more fully the processes that are regulated by the N. crassa circadian clock, systematic screens were carried out for genes that oscillate at the transcriptional level. Time-of-day-specific cDNA libraries were generated and used in differential screens to identify six new clock-controlled genes (ccgs). Transcripts specific for each of the ccgs preferentially accumulate during the late night to early morning, although they vary with respect to steady-state mRNA levels and amplitude of the rhythm. Sequencing of the ends of the new ccg cDNAs revealed that ccg-12 is identical to N. crassa cmt encoding copper metallothionein, providing the suggestion that not all clock-regulated genes in N. crassa are specifically involved in the development of conidia. This was supported by finding that half of the new ccgs, including cmt(ccg-12), are not transcriptionally induced by developmental or light signals. These data suggest a major role for the clock in the regulation of biological processes distinct from development.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biochemistry, Darmouth Medical School, Hanover, NH 03755, USA
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Bell-Pedersen D, Dunlap JC, Loros JJ. Distinct cis-acting elements mediate clock, light, and developmental regulation of the Neurospora crassa eas (ccg-2) gene. Mol Cell Biol 1996; 16:513-21. [PMID: 8552078 PMCID: PMC231029 DOI: 10.1128/mcb.16.2.513] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The Neurospora crassa eas (ccg-2) gene, which encodes a fungal hydrophobin, is transcriptionally regulated by the circadian clock. In addition, eas (ccg-2) is positively regulated by light and transcripts accumulate during asexual development. To sort out the basis of this complex regulation, deletion analyses of the eas (ccg-2) promoter were carried out to localize the cis-acting elements mediating clock, light, and developmental control. The primary sequence determinants of a positive activating clock element (ACE) were found to reside in a 45-bp region, just upstream from the TATA box. Using a novel unregulated promoter/reporter system developed for this study, we show that a 68-bp sequence encompassing the ACE is sufficient to confer clock regulation on the eas (ccg-2) gene. Electrophoretic mobility shift assays using the ACE reveal factors present in N. crassa protein extracts that recognize and bind specifically to DNA containing this element. Separate regions of the eas (ccg-2) promoter involved in light induction and developmental control are identified and shown not to be required for clock-regulated expression of eas (ccg-2). The distinct nature of the ACE validates its use as a tool for the identification of upstream regulatory factors involved in clock control of gene expression.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Dunlap JC, Loros JJ, Merrow M, Crosthwaite S, Bell-Pedersen D, Garceau N, Shinohara M, Cho H, Luo C. The genetic and molecular dissection of a prototypic circadian system. Prog Brain Res 1996; 111:11-27. [PMID: 8990904 DOI: 10.1016/s0079-6123(08)60397-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A great deal is known about this archetypal circadian system, and it is likely that Neurospora will represent the first circadian system in which it will be possible to provide a complete description of the flow of information from the photoreceptor, through the components of oscillator, out to a terminal aspect of regulation. In Neurospora the strongest case has been made for there being a state variable of clock identified (Hall, 1995), it has now been shown that light resetting of the clock is mediated by the rapid light induction of the gene encoding this state variable, and a number of defined clock-regulated output genes have been identified, in two of which the clock-specific parts of the promoters have been localized. In addition to the importance of these factoids themselves, our efforts towards understanding of this system has allowed the development of tools and paradigms (e.g. Loros et al., 1989; Loros and Dunlap, 1991; Aronson et al., 1994a) that will help to pave the way for proving the identity of clock components in more complex systems, for understanding how clocks are regulated by entraining factors, and for showing how time information eventually is used to regulate the behaviors of clock cells, and of whole organisms.
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Affiliation(s)
- J C Dunlap
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA
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Aronson BD, Bell-Pedersen D, Block GD, Bos NP, Dunlap JC, Eskin A, Garceau NY, Geusz ME, Johnson KA, Khalsa SB. Circadian rhythms. Brain Res Brain Res Rev 1993; 18:315-33. [PMID: 8401597 DOI: 10.1016/0165-0173(93)90015-r] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Circadian rhythms are a ubiquitous adaptation of eukaryotic organisms to the most reliable and predictable of environmental changes, the daily cycles of light and temperature. Prominent daily rhythms in behavior, physiology, hormone levels and biochemistry (including gene expression) are not merely responses to these environmental cycles, however, but embody the organism's ability to keep and tell time. At the core of circadian systems is a mysterious mechanism, located in the brain (actually the suprachiasmatic nucleus of the hypothalamus) of mammals, but present even in unicellular organisms, that functions as a clock. This clock drives circadian rhythms. It is independent of, but remains responsive to, environmental cycles (especially light). The interest in temporal regulation--its organization, mechanism and consequences--unites investigators in diverse disciplines studying otherwise disparate systems. This diversity is reflected in the brief reviews that summarize the presentations at a meeting on circadian rhythms held in New York City on October 31, 1992. The meeting was sponsored by the Fondation pour l'Etude du Système Nerveux (FESN) and followed a larger meeting held 18 months earlier in Geneva, whose proceedings have been published (M. Zatz (Ed.), Report of the Ninth FESN Study Group on 'Circadian Rhythms', Discussions in Neuroscience, Vol. VIII, Nos. 2 + 3, Elsevier, Amsterdam, 1992). Some speakers described progress made in the interim, while others addressed aspects of the field not previously covered.
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Affiliation(s)
- B D Aronson
- Section on Biochemical Pharmacology, National Institute of Mental Health, Bethesda, MD 20892
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Bell-Pedersen D, Dunlap JC, Loros JJ. The Neurospora circadian clock-controlled gene, ccg-2, is allelic to eas and encodes a fungal hydrophobin required for formation of the conidial rodlet layer. Genes Dev 1992; 6:2382-94. [PMID: 1459460 DOI: 10.1101/gad.6.12a.2382] [Citation(s) in RCA: 187] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Neurospora crassa clock-controlled gene (ccg-2) is transcriptionally activated by the circadian clock in a time-of-day-specific manner. Transcript and sequence analyses of ccg-2 reveal that the predicted Ccg-2 polypeptide bears significant similarity to a class of low-molecular-weight, cysteine-rich, hydrophobic proteins (hydrophobins), first identified in Schizophyllum, and including the product of the developmentally regulated Aspergillus gene, rodletless, required for spore surface rodlets. Allelism between ccg-2 and easily wettable (eas) (one of the first developmental genetic loci identified in Neurospora) was predicted on the basis of this similarity, their close genetic linkage, and previous findings demonstrating that eas mutants lack rodlets. In this study allelism is confirmed experimentally by showing that (1) transformation of an eas mutant strain with ccg-2 DNA results in phenotypic complementation, including restoration of surface rodlets, (2) inactivation of the ccg-2 gene, by RIP, results in an eas phenotype including loss of rodlet fascicles, and (3) the original eas strain has dramatically reduced levels of ccg-2 mRNA. Thus, the clock-controlled ccg-2 gene encodes an integral component of fungal asexual spores important for spore dispersal. The dramatic reduction of ccg-2 expression in the eas mutant has no apparent effect on the normal operation of the circadian clock, confirming that there is no feedback of this clock output on the oscillator itself. These data, in conjunction with the previous observation that ccg-2 is light induced, serve to focus attention on the dual interacting role of light and the circadian clock in the regulation of fungal spore development.
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Affiliation(s)
- D Bell-Pedersen
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755
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Bell-Pedersen D, Quirk SM, Bryk M, Belfort M. I-TevI, the endonuclease encoded by the mobile td intron, recognizes binding and cleavage domains on its DNA target. Proc Natl Acad Sci U S A 1991; 88:7719-23. [PMID: 1881913 PMCID: PMC52374 DOI: 10.1073/pnas.88.17.7719] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mobility of the phage T4 td intron depends on activity of an intron-encoded endonuclease (I-TevI), which cleaves a homologous intronless (delta In) target gene. The double-strand break initiates a recombination event that leads to intron transfer. We found previously that I-TevI cleaves td delta In target DNA 23-26 nucleotides upstream of the intron insertion site. DNase I-footprinting experiments and gel-shift assays indicate that I-TevI makes primary contacts around the intron insertion site. A synthetic DNA duplex spanning the insertion site but lacking the cleavage site was shown to bind I-TevI specifically, and when cloned, to direct cleavage into vector sequences. The behavior of the cloned duplex and that of deletion and insertion mutants support a primary role for sequences surrounding the insertion site in directing I-TevI binding, conferring cleavage ability, and determining cleavage polarity. On the other hand, sequences around the cleavage site were shown to influence cleavage efficiency and cut-site selection. The role of cleavage-site sequences in determining cleavage distance argues against a strict "ruler" mechanism for cleavage by I-TevI. The complex nature of the homing site recognized by this unusual type of endonuclease is considered in the context of intron spread.
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Affiliation(s)
- D Bell-Pedersen
- Molecular Genetics Program, Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509
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Bell-Pedersen D, Quirk S, Clyman J, Belfort M. Intron mobility in phage T4 is dependent upon a distinctive class of endonucleases and independent of DNA sequences encoding the intron core: mechanistic and evolutionary implications. Nucleic Acids Res 1990; 18:3763-70. [PMID: 2165250 PMCID: PMC331075 DOI: 10.1093/nar/18.13.3763] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Although mobility of the phylogenetically widespread group I introns appears to be mechanistically similar, the phage T4 intron-encoded endonucleases that promote mobility of the td and sunY introns are different from their eukaryotic counterparts. Most notably, they cleave at a distance from the intron insertion sites. The td enzyme was shown to cleave 23-26 nt 5' and the sunY endonuclease 13-15 nt 3' to the intron insertion site to generate 3-nt or 2-nt 3'-OH extensions, respectively. The absolute coconversion of exon markers between the distant cleavage and insertion sites is consistent with the double-strand-break repair model for intron mobility. As a further critical test of the model we have demonstrated that the mobility event is independent of DNA sequences that encode the catalytic intron core structure. Thus, in derivatives in which the lacZ or kanR coding sequences replace the intron, these marker genes are efficiently inserted into intron-minus alleles when the cognate endonuclease is provided in trans. The process is therefore endonuclease-dependent, rather than dependent on the intron per se. These findings, which imply that the endonucleases rather than the introns themselves were the primordial mobile elements, are incorporated into a model for the evolution of mobile introns.
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Affiliation(s)
- D Bell-Pedersen
- Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509
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Bell-Pedersen D, Quirk SM, Aubrey M, Belfort M. A site-specific endonuclease and co-conversion of flanking exons associated with the mobile td intron of phage T4. Gene 1989; 82:119-26. [PMID: 2555262 DOI: 10.1016/0378-1119(89)90036-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The product of the td intron open reading frame (ORF) of phage T4 is required for high-frequency transfer of the intervening sequence from intron-plus (In+) to intron-minus (In-) alleles. In vivo studies have demonstrated that the td ORF product targets cleavage of td In- DNA, and that cleavage is correlated with intron inheritance [Quirk et al., Cell 56 (1989) 455-465]. In the present study we show by in vitro synthesis of the td intron ORF product, that the protein possesses endonuclease activity and efficiently cleaves double-stranded DNA at or near the site of intron integration. In addition, we demonstrate that intron insertion is accompanied by co-conversion of the flanking exon sequences. Co-conversion of markers within 50 nt surrounding the site of intron insertion occurred at a high frequency (80-100%), and decreased at greater distance from the intervening sequence. Co-conversion may provide a mechanism for maintaining exon-intron RNA contacts required for accurate splicing of the relocated intron. Cleavage of target DNA by an intron endonuclease and co-conversion of flanking exon sequences are both features associated with mobile introns of eukaryotes, indicating a common mechanism for intron transfer in the eukaryotic and prokaryotic kingdoms.
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Affiliation(s)
- D Bell-Pedersen
- Wadsworth Center for Laboratory and Research, New York State Department of Health, Albany 12201-0509
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