1
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Talavera RA, Prichard BE, Sommer RA, Leitao RM, Sarabia CJ, Hazir S, Paulo JA, Gygi SP, Kellogg DR. Cell growth and nutrient availability control the mitotic exit signaling network in budding yeast. J Cell Biol 2024; 223:e202305008. [PMID: 38722822 PMCID: PMC11082370 DOI: 10.1083/jcb.202305008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 01/03/2024] [Accepted: 04/04/2024] [Indexed: 05/13/2024] Open
Abstract
Cell growth is required for cell cycle progression. The amount of growth required for cell cycle progression is reduced in poor nutrients, which leads to a reduction in cell size. In budding yeast, nutrients can influence cell size by modulating the extent of bud growth, which occurs predominantly in mitosis. However, the mechanisms are unknown. Here, we used mass spectrometry to identify proteins that modulate bud growth in response to nutrient availability. This led to the discovery that nutrients regulate numerous components of the mitotic exit network (MEN), which controls exit from mitosis. A key component of the MEN undergoes gradual multisite phosphorylation during bud growth that is dependent upon bud growth and correlated with the extent of growth. Furthermore, activation of the MEN is sufficient to override a growth requirement for mitotic exit. The data suggest a model in which the MEN ensures that mitotic exit occurs only when an appropriate amount of bud growth has occurred.
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Affiliation(s)
- Rafael A. Talavera
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Beth E. Prichard
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Robert A. Sommer
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Ricardo M. Leitao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Christopher J. Sarabia
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Semin Hazir
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Joao A. Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Douglas R. Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
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2
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Moir RD, Lavados C, Lee J, Willis IM. Functional characterization of Polr3a hypomyelinating leukodystrophy mutations in the S. cerevisiae homolog, RPC160. Gene 2020; 768:145259. [PMID: 33148458 DOI: 10.1016/j.gene.2020.145259] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/23/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022]
Abstract
Mutations in RNA polymerase III (Pol III) cause hypomeylinating leukodystrophy (HLD) and neurodegeneration in humans. POLR3A and POLR3B, the two largest Pol III subunits, together form the catalytic center and carry the majority of disease alleles. Disease-causing mutations include invariant and highly conserved residues that are predicted to negatively affect Pol III activity and decrease transcriptional output. A subset of HLD missense mutations in POLR3A cluster in the pore region that provides nucleotide access to the Pol III active site. These mutations were engineered at the corresponding positions in the Saccharomyces cerevisiae homolog, Rpc160, to evaluate their functional deficits. None of the mutations caused a growth or transcription phenotype in yeast. Each mutation was combined with a frequently occurring pore mutation, POLR3A G672E, which was also wild-type for growth and transcription. The double mutants showed a spectrum of phenotypes from wild-type to lethal, with only the least fit combinations showing an effect on Pol III transcription. In one slow-growing temperature-sensitive mutant the steady-state level of tRNAs was unaffected, however global tRNA synthesis was compromised, as was the synthesis of RPR1 and SNR52 RNAs. Affinity-purified mutant Pol III was broadly defective in both factor-independent and factor-dependent transcription in vitro across genes that represent the yeast Pol III transcriptome. Thus, the robustness of yeast Rpc160 to single Pol III leukodystrophy mutations in the pore domain can be overcome by a second mutation in the domain.
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Affiliation(s)
- Robyn D Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Christian Lavados
- Graduate Program in Biomedical Science, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - JaeHoon Lee
- Department of Medicine (Cardiology), Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ian M Willis
- Departments of Biochemistry and Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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3
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Ahmed K, Carter DE, Lajoie P. Hyperactive
TORC
1 sensitizes yeast cells to endoplasmic reticulum stress by compromising cell wall integrity. FEBS Lett 2019; 593:1957-1973. [DOI: 10.1002/1873-3468.13463] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 05/17/2019] [Indexed: 12/20/2022]
Affiliation(s)
- Khadija Ahmed
- Department of Anatomy and Cell Biology The University of Western Ontario London Canada
| | - David E. Carter
- Robarts Research Institute The University of Western Ontario London Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology The University of Western Ontario London Canada
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4
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Davis RB, Likhite N, Jackson CA, Liu T, Yu MC. Robust repression of tRNA gene transcription during stress requires protein arginine methylation. Life Sci Alliance 2019; 2:2/3/e201800261. [PMID: 31160378 PMCID: PMC6549136 DOI: 10.26508/lsa.201800261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 05/21/2019] [Accepted: 05/22/2019] [Indexed: 02/06/2023] Open
Abstract
Protein arginine methylation is an important means by which protein function can be regulated. In the budding yeast, this modification is catalyzed by the major protein arginine methyltransferase Hmt1. Here, we provide evidence that the Hmt1-mediated methylation of Rpc31, a subunit of RNA polymerase III, plays context-dependent roles in tRNA gene transcription: under conditions optimal for growth, it positively regulates tRNA gene transcription, and in the setting of stress, it promotes robust transcriptional repression. In the context of stress, methylation of Rpc31 allows for its optimal interaction with RNA polymerase III global repressor Maf1. Interestingly, mammalian Hmt1 homologue is able to methylate one of Rpc31's human homologue, RPC32β, but not its paralogue, RPC32α. Our data led us to propose an efficient model whereby protein arginine methylation facilitates metabolic economy and coordinates protein-synthetic capacity.
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Affiliation(s)
- Richoo B Davis
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Neah Likhite
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Christopher A Jackson
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Tao Liu
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Michael C Yu
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY, USA
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5
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Szatkowska R, Garcia-Albornoz M, Roszkowska K, Holman SW, Furmanek E, Hubbard SJ, Beynon RJ, Adamczyk M. Glycolytic flux in Saccharomyces cerevisiae is dependent on RNA polymerase III and its negative regulator Maf1. Biochem J 2019; 476:1053-1082. [PMID: 30885983 PMCID: PMC6448137 DOI: 10.1042/bcj20180701] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 03/11/2019] [Accepted: 03/15/2019] [Indexed: 02/07/2023]
Abstract
Protein biosynthesis is energetically costly, is tightly regulated and is coupled to stress conditions including glucose deprivation. RNA polymerase III (RNAP III)-driven transcription of tDNA genes for production of tRNAs is a key element in efficient protein biosynthesis. Here we present an analysis of the effects of altered RNAP III activity on the Saccharomyces cerevisiae proteome and metabolism under glucose-rich conditions. We show for the first time that RNAP III is tightly coupled to the glycolytic system at the molecular systems level. Decreased RNAP III activity or the absence of the RNAP III negative regulator, Maf1 elicit broad changes in the abundance profiles of enzymes engaged in fundamental metabolism in S. cerevisiae In a mutant compromised in RNAP III activity, there is a repartitioning towards amino acids synthesis de novo at the expense of glycolytic throughput. Conversely, cells lacking Maf1 protein have greater potential for glycolytic flux.
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Affiliation(s)
- Roza Szatkowska
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland
| | - Manuel Garcia-Albornoz
- Division of Evolution & Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, U.K
| | - Katarzyna Roszkowska
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland
| | - Stephen W Holman
- Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Emil Furmanek
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland
| | - Simon J Hubbard
- Division of Evolution & Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, U.K
| | - Robert J Beynon
- Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool, U.K
| | - Malgorzata Adamczyk
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland
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6
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Sphingolipid/Pkh1/2-TORC1/Sch9 Signaling Regulates Ribosome Biogenesis in Tunicamycin-Induced Stress Response in Yeast. Genetics 2019; 212:175-186. [PMID: 30824472 DOI: 10.1534/genetics.118.301874] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 02/26/2019] [Indexed: 12/26/2022] Open
Abstract
Reduced ribosome biogenesis in response to environmental conditions is a key feature of cell adaptation to stress. For example, ribosomal genes are transcriptionally repressed when cells are exposed to tunicamycin, a protein glycosylation inhibitor that induces endoplasmic reticulum stress and blocks vesicular trafficking in the secretory pathway. Here, we describe a novel regulatory model, in which tunicamycin-mediated stress induces the accumulation of long-chain sphingoid bases and subsequent activation of Pkh1/2 signaling, which leads to decreased expression of ribosomal protein genes via the downstream effectors Pkc1 and Sch9. Target of rapamycin complex 1 (TORC1), an upstream activator of Sch9, is also required. This pathway links ribosome biogenesis to alterations in membrane lipid composition under tunicamycin-induced stress conditions. Our results suggest that sphingolipid/Pkh1/2-TORC1/Sch9 signaling is an important determinant for adaptation to tunicamycin-induced stress.
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7
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Walters AD, Amoateng K, Wang R, Chen JH, McDermott G, Larabell CA, Gadal O, Cohen-Fix O. Nuclear envelope expansion in budding yeast is independent of cell growth and does not determine nuclear volume. Mol Biol Cell 2018; 30:131-145. [PMID: 30379612 PMCID: PMC6337908 DOI: 10.1091/mbc.e18-04-0204] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Most cells exhibit a constant ratio between nuclear and cell volume. The mechanism dictating this constant ratio and the nuclear component(s) that scale with cell size are not known. To address this, we examined the consequences to the size and shape of the budding yeast nucleus when cell expansion is inhibited by down-regulating components of the secretory pathway. We find that under conditions where cell size increase is restrained, the nucleus becomes bilobed, with the bulk of the DNA in one lobe and the nucleolus in the other. The formation of bilobed nuclei is dependent on fatty acid and phospholipid synthesis, suggesting that it is associated with nuclear membrane expansion. Bilobed nuclei appeared predominantly after spindle pole body separation, suggesting that nuclear envelope expansion follows cell-cycle cues rather than cell size. Importantly, cells with bilobed nuclei had the same nuclear:cell volume ratio as cells with round nuclei. Therefore, the bilobed nucleus could be a consequence of continued NE expansion as cells traverse the cell cycle without an accompanying increase in nuclear volume due to the inhibition of cell growth. Our data suggest that nuclear volume is not determined by nuclear envelope availability but by one or more nucleoplasmic factors.
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Affiliation(s)
- Alison D Walters
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Kwabena Amoateng
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Renjie Wang
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 31000 Toulouse, France
| | - Jian-Hua Chen
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Gerry McDermott
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Carolyn A Larabell
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158.,Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Olivier Gadal
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 31000 Toulouse, France
| | - Orna Cohen-Fix
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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8
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Willis IM, Moir RD. Signaling to and from the RNA Polymerase III Transcription and Processing Machinery. Annu Rev Biochem 2018; 87:75-100. [PMID: 29328783 DOI: 10.1146/annurev-biochem-062917-012624] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RNA polymerase (Pol) III has a specialized role in transcribing the most abundant RNAs in eukaryotic cells, transfer RNAs (tRNAs), along with other ubiquitous small noncoding RNAs, many of which have functions related to the ribosome and protein synthesis. The high energetic cost of producing these RNAs and their central role in protein synthesis underlie the robust regulation of Pol III transcription in response to nutrients and stress by growth regulatory pathways. Downstream of Pol III, signaling impacts posttranscriptional processes affecting tRNA function in translation and tRNA cleavage into smaller fragments that are increasingly attributed with novel cellular activities. In this review, we consider how nutrients and stress control Pol III transcription via its factors and its negative regulator, Maf1. We highlight recent work showing that the composition of the tRNA population and the function of individual tRNAs is dynamically controlled and that unrestrained Pol III transcription can reprogram central metabolic pathways.
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Affiliation(s)
- Ian M Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA; , .,Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robyn D Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA; ,
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9
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Clarke J, Dephoure N, Horecka I, Gygi S, Kellogg D. A conserved signaling network monitors delivery of sphingolipids to the plasma membrane in budding yeast. Mol Biol Cell 2017; 28:2589-2599. [PMID: 28794263 PMCID: PMC5620368 DOI: 10.1091/mbc.e17-01-0081] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 07/28/2017] [Accepted: 08/02/2017] [Indexed: 12/16/2022] Open
Abstract
In budding yeast, signals generated in response to membrane growth are required for cell cycle progression. A mass spectrometry screen for signals triggered by an arrest of membrane growth identified sphingolipid signaling pathways. Delivery of sphingolipids to the plasma membrane could generate signals that control cell growth and the cell cycle. In budding yeast, cell cycle progression and ribosome biogenesis are dependent on plasma membrane growth, which ensures that events of cell growth are coordinated with each other and with the cell cycle. However, the signals that link the cell cycle and ribosome biogenesis to membrane growth are poorly understood. Here we used proteome-wide mass spectrometry to systematically discover signals associated with membrane growth. The results suggest that membrane trafficking events required for membrane growth generate sphingolipid-dependent signals. A conserved signaling network appears to play an essential role in signaling by responding to delivery of sphingolipids to the plasma membrane. In addition, sphingolipid-dependent signals control phosphorylation of protein kinase C (Pkc1), which plays an essential role in the pathways that link the cell cycle and ribosome biogenesis to membrane growth. Together these discoveries provide new clues as to how growth-dependent signals control cell growth and the cell cycle.
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Affiliation(s)
- Jesse Clarke
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Noah Dephoure
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10021
| | - Ira Horecka
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Steven Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Douglas Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
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10
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Thai V, Dephoure N, Weiss A, Ferguson J, Leitao R, Gygi SP, Kellogg DR. Protein Kinase C Controls Binding of Igo/ENSA Proteins to Protein Phosphatase 2A in Budding Yeast. J Biol Chem 2017; 292:4925-4941. [PMID: 28100785 DOI: 10.1074/jbc.m116.753004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 01/09/2017] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase 2A (PP2A) plays important roles in controlling mitosis in all eukaryotic cells. The form of PP2A that controls mitosis is associated with a conserved regulatory subunit that is called B55 in vertebrates and Cdc55 in budding yeast. The activity of this form of PP2A can be inhibited by binding of conserved Igo/ENSA proteins. Although the mechanisms that activate Igo/ENSA to bind and inhibit PP2A are well understood, little is known about how Igo/Ensa are inactivated. Here, we have analyzed regulation of Igo/ENSA in the context of a checkpoint pathway that links mitotic entry to membrane growth in budding yeast. Protein kinase C (Pkc1) relays signals in the pathway by activating PP2ACdc55 We discovered that constitutively active Pkc1 can drive cells through a mitotic checkpoint arrest, which suggests that Pkc1-dependent activation of PP2ACdc55 plays a critical role in checkpoint signaling. We therefore used mass spectrometry to determine how Pkc1 modifies the PP2ACdc55 complex. This revealed that Pkc1 induces changes in the phosphorylation of multiple subunits of the complex, as well as dissociation of Igo/ENSA. Pkc1 directly phosphorylates Cdc55 and Igo/ENSA, and phosphorylation site mapping and mutagenesis indicate that phosphorylation of Cdc55 contributes to Igo/ENSA dissociation. Association of Igo2 with PP2ACdc55 is regulated during the cell cycle, yet mutation of Pkc1-dependent phosphorylation sites on Cdc55 and Igo2 did not cause defects in mitotic progression. Together, the data suggest that Pkc1 controls PP2ACdc55 by multiple overlapping mechanisms.
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Affiliation(s)
- Vu Thai
- From the Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Noah Dephoure
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10021, and
| | - Amit Weiss
- From the Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Jacqueline Ferguson
- From the Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Ricardo Leitao
- From the Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Steven P Gygi
- the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Douglas R Kellogg
- From the Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, California 95064,
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11
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Yabuki Y, Katayama M, Kodama Y, Sakamoto A, Yatsuhashi A, Funato K, Mizuta K. Arp2/3 complex and Mps3 are required for regulation of ribosome biosynthesis in the secretory stress response. Yeast 2017; 34:155-163. [PMID: 27862269 DOI: 10.1002/yea.3221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 10/18/2016] [Accepted: 11/03/2016] [Indexed: 11/11/2022] Open
Abstract
Secretory defects cause transcriptional repression of ribosome biogenesis in Saccharomyces cerevisiae. However, the molecular mechanism underlying secretory defect-induced transcriptional repression of ribosome biogenesis remains to be fully elucidated. In this study, we demonstrated that the Arp2/3 complex was required for reduction of ribosome protein gene expression in response to defective secretion by addition of tunicamycin. Two cmd1 mutants, cmd1-228 and cmd1-239 that cause mislocalization of calmodulin and defective mitotic spindle formation, respectively, failed to interact with Arc35, a component of the Arp2/3 complex. These mutants also caused defects in the reduction of ribosome protein gene expression induced by secretory blockade. A mutation in TUB4 (tub4-1), whose product has an essential function in microtubule organization, showed a similar response. In addition, we showed that the response to a secretory defect required SUN protein Mps3, which was localized at the nuclear envelope and involved in spindle pole body assembly. These results suggest that the Arp2/3 complex is required to transmit signals resulting from secretory blockade, and that the spindle pole body functions as a transit point from cytoplasm to Mps3 at the nuclear envelope. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Yukari Yabuki
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Masako Katayama
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Yushi Kodama
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Akiko Sakamoto
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Ayumi Yatsuhashi
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Kouichi Funato
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
| | - Keiko Mizuta
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, 739-8528, Japan
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12
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Ribosome quality control is a central protection mechanism for yeast exposed to deoxynivalenol and trichothecin. BMC Genomics 2016; 17:417. [PMID: 27245696 PMCID: PMC4888481 DOI: 10.1186/s12864-016-2718-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/10/2016] [Indexed: 11/25/2022] Open
Abstract
Background The trichothecene mycotoxins deoxynivalenol (DON) and trichothecin (TTC) are inhibitors of eukaryotic protein synthesis. Their effect on cellular homeostasis is poorly understood. We report a systematic functional investigation of the effect of DON and TTC on the yeast Saccharomyces cerevisiae using genetic array, network and microarray analysis. To focus the genetic analysis on intracellular consequences of toxin action we eliminated the PDR5 gene coding for a potent pleiotropic drug efflux protein potentially confounding results. We therefore used a knockout library with a pdr5Δ strain background. Results DON or TTC treatment creates a fitness bottleneck connected to ribosome efficiency. Genes isolated by systematic genetic array analysis as contributing to toxin resistance function in ribosome quality control, translation fidelity, and in transcription. Mutants in the E3 ligase Hel2, involved in ribosome quality control, and several members of the Rpd3 histone deacetylase complex were highly sensitive to DON. DON and TTC have similar genetic profiles despite their different toxic potency. Network analysis shows a coherent and tight network of genetic interactions among the DON and TTC resistance conferring gene products. The networks exhibited topological properties commonly associated with efficient processing of information. Many sensitive mutants have a "slow growth" gene expression signature. DON-exposed yeast cells increase transcripts of ribosomal protein and histone genes indicating an internal signal for growth enhancement. Conclusions The combination of gene expression profiling and analysis of mutants reveals cellular pathways which become bottlenecks under DON and TTC stress. These are generally directly or indirectly connected to ribosome biosynthesis such as the general secretory pathway, cytoskeleton, cell cycle delay, ribosome synthesis and translation quality control. Gene expression profiling points to an increased demand of ribosomal components and does not reveal activation of stress pathways. Our analysis highlights ribosome quality control and a contribution of a histone deacetylase complex as main sources of resistance against DON and TTC. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2718-y) contains supplementary material, which is available to authorized users.
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13
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Bonhoure N, Byrnes A, Moir RD, Hodroj W, Preitner F, Praz V, Marcelin G, Chua SC, Martinez-Lopez N, Singh R, Moullan N, Auwerx J, Willemin G, Shah H, Hartil K, Vaitheesvaran B, Kurland I, Hernandez N, Willis IM. Loss of the RNA polymerase III repressor MAF1 confers obesity resistance. Genes Dev 2015; 29:934-47. [PMID: 25934505 PMCID: PMC4421982 DOI: 10.1101/gad.258350.115] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
MAF1 is a global repressor of RNA polymerase III transcription that regulates the expression of highly abundant noncoding RNAs in response to nutrient availability and cellular stress. Thus, MAF1 function is thought to be important for metabolic economy. Here we show that a whole-body knockout of Maf1 in mice confers resistance to diet-induced obesity and nonalcoholic fatty liver disease by reducing food intake and increasing metabolic inefficiency. Energy expenditure in Maf1(-/-) mice is increased by several mechanisms. Precursor tRNA synthesis was increased in multiple tissues without significant effects on mature tRNA levels, implying increased turnover in a futile tRNA cycle. Elevated futile cycling of hepatic lipids was also observed. Metabolite profiling of the liver and skeletal muscle revealed elevated levels of many amino acids and spermidine, which links the induction of autophagy in Maf1(-/-) mice with their extended life span. The increase in spermidine was accompanied by reduced levels of nicotinamide N-methyltransferase, which promotes polyamine synthesis, enables nicotinamide salvage to regenerate NAD(+), and is associated with obesity resistance. Consistent with this, NAD(+) levels were increased in muscle. The importance of MAF1 for metabolic economy reveals the potential for MAF1 modulators to protect against obesity and its harmful consequences.
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Affiliation(s)
- Nicolas Bonhoure
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Ashlee Byrnes
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robyn D Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Wassim Hodroj
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Frédéric Preitner
- Mouse Metabolic Evaluation Facility, Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland
| | - Viviane Praz
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Genevieve Marcelin
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Streamson C Chua
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA; Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Nuria Martinez-Lopez
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Rajat Singh
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA; Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Norman Moullan
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Johan Auwerx
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Gilles Willemin
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland; Mouse Metabolic Evaluation Facility, Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland
| | - Hardik Shah
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Kirsten Hartil
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Bhavapriya Vaitheesvaran
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Irwin Kurland
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA; Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Nouria Hernandez
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland;
| | - Ian M Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA; Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA;
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14
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Lee J, Moir RD, Willis IM. Differential Phosphorylation of RNA Polymerase III and the Initiation Factor TFIIIB in Saccharomyces cerevisiae. PLoS One 2015; 10:e0127225. [PMID: 25970584 PMCID: PMC4430316 DOI: 10.1371/journal.pone.0127225] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/13/2015] [Indexed: 11/19/2022] Open
Abstract
The production of ribosomes and tRNAs for protein synthesis has a high energetic cost and is under tight transcriptional control to ensure that the level of RNA synthesis is balanced with nutrient availability and the prevailing environmental conditions. In the RNA polymerase (pol) III system in yeast, nutrients and stress affect transcription through a bifurcated signaling pathway in which protein kinase A (PKA) and TORC1 activity directly or indirectly, through downstream kinases, alter the phosphorylation state and function of the Maf1 repressor and Rpc53, a TFIIF-like subunit of the polymerase. However, numerous lines of evidence suggest greater complexity in the regulatory network including the phosphoregulation of other pol III components. To address this issue, we systematically examined all 17 subunits of pol III along with the three subunits of the initiation factor TFIIIB for evidence of differential phosphorylation in response to inhibition of TORC1. A relatively high stoichiometry of phosphorylation was observed for several of these proteins and the Rpc82 subunit of the polymerase and the Bdp1 subunit of TFIIIB were found to be differentially phosphorylated. Bdp1 is phosphorylated on four major sites during exponential growth and the protein is variably dephosphorylated under conditions that inhibit tRNA gene transcription. PKA, the TORC1-regulated kinase Sch9 and protein kinase CK2 are all implicated in the phosphorylation of Bdp1. Alanine substitutions at the four phosphosites cause hyper-repression of transcription indicating that phosphorylation of Bdp1 opposes Maf1-mediated repression. The new findings suggest an integrated regulatory model for signaling events controlling pol III transcription.
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Affiliation(s)
- Jaehoon Lee
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Robyn D. Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (RDM); (IMW)
| | - Ian M. Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (RDM); (IMW)
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15
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Jordán-Pla A, Gupta I, de Miguel-Jiménez L, Steinmetz LM, Chávez S, Pelechano V, Pérez-Ortín JE. Chromatin-dependent regulation of RNA polymerases II and III activity throughout the transcription cycle. Nucleic Acids Res 2014; 43:787-802. [PMID: 25550430 PMCID: PMC4333398 DOI: 10.1093/nar/gku1349] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The particular behaviour of eukaryotic RNA polymerases along different gene regions and amongst distinct gene functional groups is not totally understood. To cast light onto the alternative active or backtracking states of RNA polymerase II, we have quantitatively mapped active RNA polymerases at a high resolution following a new biotin-based genomic run-on (BioGRO) technique. Compared with conventional profiling with chromatin immunoprecipitation, the analysis of the BioGRO profiles in Saccharomyces cerevisiae shows that RNA polymerase II has unique activity profiles at both gene ends, which are highly dependent on positioned nucleosomes. This is the first demonstration of the in vivo influence of positioned nucleosomes on transcription elongation. The particular features at the 5' end and around the polyadenylation site indicate that this polymerase undergoes extensive specific-activity regulation in the initial and final transcription elongation phases. The genes encoding for ribosomal proteins show distinctive features at both ends. BioGRO also provides the first nascentome analysis for RNA polymerase III, which indicates that transcription of tRNA genes is poorly regulated at the individual copy level. The present study provides a novel perspective of the transcription cycle that incorporates inactivation/reactivation as an important aspect of RNA polymerase dynamics.
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Affiliation(s)
- Antonio Jordán-Pla
- Departamento de Bioquímica y Biología Molecular and ERI Biotecmed, Facultad de Biológicas, Universitat de València, C/Dr. Moliner 50, E46100 Burjassot, Spain
| | - Ishaan Gupta
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Lola de Miguel-Jiménez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, 41013 Seville, Spain
| | - Lars M Steinmetz
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany Stanford University School of Medicine, Department of Genetics, Stanford, CA 94305, USA Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA
| | - Sebastián Chávez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Virgen del Rocío-CSIC-Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, 41013 Seville, Spain
| | - Vicent Pelechano
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - José E Pérez-Ortín
- Departamento de Bioquímica y Biología Molecular and ERI Biotecmed, Facultad de Biológicas, Universitat de València, C/Dr. Moliner 50, E46100 Burjassot, Spain
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16
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Abstract
During environmental, developmental, or genetic stress, the cell's folding capacity can become overwhelmed, and misfolded proteins can accumulate in all cell compartments. Eukaryotes evolved the unfolded protein response (UPR) to counteract proteotoxic stress in the endoplasmic reticulum (ER). Although the UPR is vital to restoring homeostasis to protein folding in the ER, it has become evident that the response to ER stress is not limited to the UPR. Here, we used engineered orthogonal UPR induction, deep mRNA sequencing, and dynamic flow cytometry to dissect the cell's response to ER stress comprehensively. We show that budding yeast augments the UPR with time-delayed Ras/PKA signaling. This second wave of transcriptional dynamics is independent of the UPR and is necessary for fitness in the presence of ER stress, partially due to a reduction in general protein synthesis. This Ras/PKA-mediated effect functionally mimics other mechanisms, such as translational control by PKR-like ER kinase (PERK) and regulated inositol-requiring enzyme 1 (IRE1)-dependent mRNA decay (RIDD), which reduce the load of proteins entering the ER in response to ER stress in metazoan cells.
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17
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Miyakawa T, Mizunuma M. Physiological Roles of Calcineurin inSaccharomyces cerevisiaewith Special Emphasis on Its Roles in G2/M Cell-Cycle Regulation. Biosci Biotechnol Biochem 2014; 71:633-45. [PMID: 17341827 DOI: 10.1271/bbb.60495] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Calcineurin, a highly conserved Ca(2+)/CaM-dependent protein phosphatase, plays key regulatory roles in diverse biological processes from yeast to humans. Genetic and molecular analyses of the yeast model system have proved successful in dissecting complex regulatory pathways mediated by calcineurin. Saccharomyces cerevisiae calcineurin is not essential for growth under laboratory conditions, but becomes essential for survival under certain stress conditions, and is required for stress-induced expression of the genes for ion transporters and cell-wall synthesis. Yeast calcineurin, in collaboration with a Mpk1 MAP kinase cascade, is also important in G(2) cell-cycle regulation due to its action in a checkpoint-like mechanism. Genetic and molecular analysis of the Ca(2+)-dependent cell-cycle regulation has revealed an elaborate mechanism for the calcineurin-dependent regulation of the G(2)/M transition, in which calcineurin multilaterally activates Swe1, a negative regulator of the Cdc28/Clb complex, at the transcriptional, posttranslational, and degradation levels.
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Affiliation(s)
- Tokichi Miyakawa
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan.
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18
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A Ribosome Assembly Factor Ebp2p, the Yeast Homolog of EBNA1-Binding Protein 2, Is Involved in the Secretory Response. Biosci Biotechnol Biochem 2014; 72:1080-6. [DOI: 10.1271/bbb.70817] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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19
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Yabuki Y, Kodama Y, Katayama M, Sakamoto A, Kanemaru H, Wan K, Mizuta K. Glycogen synthase kinase-3 is involved in regulation of ribosome biogenesis in yeast. Biosci Biotechnol Biochem 2014; 78:800-5. [PMID: 25035982 DOI: 10.1080/09168451.2014.905183] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Secretory defects cause transcriptional repression of both ribosomal proteins and ribosomal RNA genes in Saccharomyces cerevisiae. Rrs1, a trans-acting factor that participates in ribosome biogenesis, is involved in the signaling pathway induced by secretory defects. Here, we found that Rrs1 interacts with two homologs of the glycogen synthase kinase-3 (GSK-3), Rim11, and Mrk1. Rrs1 possesses a repetitive consensus amino acid sequence for phosphorylation by GSK-3, and mutation of this sequence abolished the interaction of Rrs1 with Rim11 and Mrk1. Although this mutation did not affect vegetative cell growth or secretory response, disruption of all four genes encoding GSK-3 homologs, especially Mck1, diminished the transcriptional repression of ribosomal protein genes in response to secretory defects. Among the four GSK-3 kinases, Mck1 appears to be the primary mediator of this response, while the other GSK-3 kinases contribute redundantly.
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Affiliation(s)
- Yukari Yabuki
- a Department of Biofunctional Science and Technology , Graduate School of Biosphere Science, Hiroshima University , Higashi-Hiroshima , Japan
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20
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Low YS, Bircham PW, Maass DR, Atkinson PH. Kinetochore genes are required to fully activate secretory pathway expansion in S. cerevisiae under induced ER stress. MOLECULAR BIOSYSTEMS 2014; 10:1790-802. [PMID: 24722431 DOI: 10.1039/c3mb70414a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Basal ER stress occurs when proteins misfold in normal physiological conditions and are corrected by the unfolded protein response (UPR). Elevated ER stress occurs when misfolding is refractory as found in numerous diseases such as atherosclerosis, Type II diabetes and some cancers. In elevated ER stress it is unclear whether cells utilise the same or different networks of genes as in basal levels of ER stress. To probe this question, we used secretory pathway reporters Yip3p-GFP, Erv29p-GFP, Orm2p-GFP and UPREpr-GFP placed on the yeast deletion mutant array (DMA) genetic background. The reporter's expression levels, measured by automated microscopy, at basal versus elevated ER stress induced by the over-expression of CPY* were compared. A novel group of kinetochore genes (CTF19 complex) were found to be uniquely required for full induction of all four ER stress reporters in elevated stress. A follow-up reporter screen was developed by mating the ctf19Δ kinetochore gene deletion strain into the genome-wide XXXp-GFP tagged library then testing with over-expressed CPY*. This screen identified Bcy1p and Bfr1p as possible signalling points that down-regulate the UPR and secretory pathway when kinetochore proteins are absent under elevated stress conditions. Bfr1p appears to be a checkpoint that monitors the integrity of kinetochores at increased levels of ER stress. This study concludes that functional kinetochores are required for full activation of the secretory pathway in elevated ER stress and that the responses to basal and elevated levels of ER stress require different networks of genes.
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Affiliation(s)
- Yee S Low
- School of Biological Sciences, Victoria University of Wellington, Kelburn Parade, Wellington, New Zealand.
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21
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Mod5 protein binds to tRNA gene complexes and affects local transcriptional silencing. Proc Natl Acad Sci U S A 2013; 110:E3081-9. [PMID: 23898186 DOI: 10.1073/pnas.1219946110] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The tRNA gene-mediated (tgm) silencing of RNA polymerase II promoters is dependent on subnuclear clustering of the tRNA genes, but genetic analysis shows that the silencing requires additional mechanisms. We have identified proteins that bind tRNA gene transcription complexes and are required for tgm silencing but not required for gene clustering. One of the proteins, Mod5, is a tRNA modifying enzyme that adds an N6-isopentenyl adenosine modification at position 37 on a small number of tRNAs in the cytoplasm, although a subpopulation of Mod5 is also found in the nucleus. Recent publications have also shown that Mod5 has tumor suppressor characteristics in humans as well as confers drug resistance through prion-like misfolding in yeast. Here, we show that a subpopulation of Mod5 associates with tRNA gene complexes in the nucleolus. This association occurs and is required for tgm silencing regardless of whether the pre-tRNA transcripts are substrates for Mod5 modification. In addition, Mod5 is bound to nuclear pre-tRNA transcripts, although they are not substrates for the A37 modification. Lastly, we show that truncation of the tRNA transcript to remove the normal tRNA structure also alleviates silencing, suggesting that synthesis of intact pre-tRNAs is required for the silencing mechanism. These results are discussed in light of recent results showing that silencing near tRNA genes also requires chromatin modification.
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22
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Lee YJ, Lee CY, Grzechnik A, Gonzales-Zubiate F, Vashisht AA, Lee A, Wohlschlegel J, Chanfreau GF. RNA polymerase I stability couples cellular growth to metal availability. Mol Cell 2013; 51:105-15. [PMID: 23747013 DOI: 10.1016/j.molcel.2013.05.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 03/28/2013] [Accepted: 05/02/2013] [Indexed: 10/26/2022]
Abstract
Zinc is an essential cofactor of all major eukaryotic RNA polymerases. How the activity of these enzymes is coordinated or regulated according to cellular zinc levels is largely unknown. Here we show that the stability of RNA polymerase I (RNAPI) is tightly coupled to zinc availability in vivo. In zinc deficiency, RNAPI is specifically degraded by proteolysis in the vacuole in a pathway dependent on the export in Xpo1p and deubiquitination of the RNAPI large subunit Rpa190p by Ubp2p and Ubp4p. RNAPII is unaffected, which allows for the expression of genes required in zinc deficiency. RNAPI export to the vacuole is required for survival during zinc starvation, suggesting that degradation of zinc-binding subunits might provide a last resort zinc reservoir. These results reveal a hierarchy of cellular transcriptional activities during zinc starvation and show that degradation of the most active cellular transcriptional machinery couples cellular growth and proliferation to zinc availability.
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Affiliation(s)
- Yueh-Jung Lee
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA
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23
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Moir RD, Willis IM. Regulation of pol III transcription by nutrient and stress signaling pathways. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:361-75. [PMID: 23165150 DOI: 10.1016/j.bbagrm.2012.11.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 12/29/2022]
Abstract
Transcription by RNA polymerase III (pol III) is responsible for ~15% of total cellular transcription through the generation of small structured RNAs such as tRNA and 5S RNA. The coordinate synthesis of these molecules with ribosomal protein mRNAs and rRNA couples the production of ribosomes and their tRNA substrates and balances protein synthetic capacity with the growth requirements of the cell. Ribosome biogenesis in general and pol III transcription in particular is known to be regulated by nutrient availability, cell stress and cell cycle stage and is perturbed in pathological states. High throughput proteomic studies have catalogued modifications to pol III subunits, assembly, initiation and accessory factors but most of these modifications have yet to be linked to functional consequences. Here we review our current understanding of the major points of regulation in the pol III transcription apparatus, the targets of regulation and the signaling pathways known to regulate their function. This article is part of a Special Issue entitled: Transcription by Odd Pols.
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Affiliation(s)
- Robyn D Moir
- Departments of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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24
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McCusker D, Kellogg DR. Plasma membrane growth during the cell cycle: unsolved mysteries and recent progress. Curr Opin Cell Biol 2012; 24:845-51. [PMID: 23141634 DOI: 10.1016/j.ceb.2012.10.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 10/11/2012] [Accepted: 10/15/2012] [Indexed: 11/28/2022]
Abstract
Growth of the plasma membrane is as fundamental to cell reproduction as DNA replication, chromosome segregation and ribosome biogenesis, yet little is known about the underlying mechanisms. Membrane growth during the cell cycle requires mechanisms that control the initiation, location, and extent of membrane growth, as well as mechanisms that coordinate membrane growth with cell cycle progression. Recent experiments have established links between membrane growth and core cell cycle regulators. Further analysis of these links will yield insights into conserved and fundamental mechanisms of cell growth. A better understanding of the post-Golgi pathways by which membrane growth occurs will be essential for future progress.
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Affiliation(s)
- Derek McCusker
- European Institute of Chemistry and Biology, 2 rue Robert Escarpit, 33607 Pessac, France
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25
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Moir RD, Gross DA, Silver DL, Willis IM. SCS3 and YFT2 link transcription of phospholipid biosynthetic genes to ER stress and the UPR. PLoS Genet 2012; 8:e1002890. [PMID: 22927826 PMCID: PMC3426550 DOI: 10.1371/journal.pgen.1002890] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 06/19/2012] [Indexed: 11/21/2022] Open
Abstract
The ability to store nutrients in lipid droplets (LDs) is an ancient function that provides the primary source of metabolic energy during periods of nutrient insufficiency and between meals. The Fat storage-Inducing Transmembrane (FIT) proteins are conserved ER–resident proteins that facilitate fat storage by partitioning energy-rich triglycerides into LDs. FIT2, the ancient ortholog of the FIT gene family first identified in mammals has two homologs in Saccharomyces cerevisiae (SCS3 and YFT2) and other fungi of the Saccharomycotina lineage. Despite the coevolution of these genes for more than 170 million years and their divergence from higher eukaryotes, SCS3, YFT2, and the human FIT2 gene retain some common functions: expression of the yeast genes in a human embryonic kidney cell line promotes LD formation, and expression of human FIT2 in yeast rescues the inositol auxotrophy and chemical and genetic phenotypes of strains lacking SCS3. To better understand the function of SCS3 and YFT2, we investigated the chemical sensitivities of strains deleted for either or both genes and identified synthetic genetic interactions against the viable yeast gene-deletion collection. We show that SCS3 and YFT2 have shared and unique functions that connect major biosynthetic processes critical for cell growth. These include lipid metabolism, vesicular trafficking, transcription of phospholipid biosynthetic genes, and protein synthesis. The genetic data indicate that optimal strain fitness requires a balance between phospholipid synthesis and protein synthesis and that deletion of SCS3 and YFT2 impacts a regulatory mechanism that coordinates these processes. Part of this mechanism involves a role for SCS3 in communicating changes in the ER (e.g. due to low inositol) to Opi1-regulated transcription of phospholipid biosynthetic genes. We conclude that SCS3 and YFT2 are required for normal ER membrane biosynthesis in response to perturbations in lipid metabolism and ER stress. The ability to form lipid droplets is a conserved property of eukaryotic cells that allows the storage of excess metabolic energy in a form that can be readily accessed. In adipose tissue, the storage of excess calories in lipid droplets normally protects other tissues from lipotoxicity and insulin resistance, but this protection is lost with chronic over-nutrition. The FAT storage-inducing transmembrane (FIT) proteins were recently identified as a conserved family of proteins that reside in the lipid bilayer of the endoplasmic reticulum and are implicated in lipid droplet formation. In this work we show that specific functions of the FIT proteins are conserved between yeast and humans and that SCS3 and YFT2, the yeast homologs of mammalian FIT2, are part of a large genetic interaction network connecting lipid metabolism, vesicle trafficking, transcription, and protein synthesis. From these interactions we determined that yeast strains lacking SCS3 and YFT2 are defective in their response to chronic ER stress and cannot induce the unfolded protein response pathway or transcription of phospholipid biosynthetic genes in low inositol. Our findings suggest that the mammalian FIT genes may play an important role in ER stress pathways, which are linked to obesity and type 2 diabetes.
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Affiliation(s)
- Robyn D. Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David A. Gross
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke–NUS Graduate Medical School Singapore, Singapore, Singapore
| | - David L. Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke–NUS Graduate Medical School Singapore, Singapore, Singapore
- * E-mail: (IMW); (DLS)
| | - Ian M. Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (IMW); (DLS)
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26
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Anastasia SD, Nguyen DL, Thai V, Meloy M, MacDonough T, Kellogg DR. A link between mitotic entry and membrane growth suggests a novel model for cell size control. ACTA ACUST UNITED AC 2012; 197:89-104. [PMID: 22451696 PMCID: PMC3317797 DOI: 10.1083/jcb.201108108] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Addition of new membrane to the cell surface by membrane trafficking is necessary for cell growth. In this paper, we report that blocking membrane traffic causes a mitotic checkpoint arrest via Wee1-dependent inhibitory phosphorylation of Cdk1. Checkpoint signals are relayed by the Rho1 GTPase, protein kinase C (Pkc1), and a specific form of protein phosphatase 2A (PP2A(Cdc55)). Signaling via this pathway is dependent on membrane traffic and appears to increase gradually during polar bud growth. We hypothesize that delivery of vesicles to the site of bud growth generates a signal that is proportional to the extent of polarized membrane growth and that the strength of the signal is read by downstream components to determine when sufficient growth has occurred for initiation of mitosis. Growth-dependent signaling could explain how membrane growth is integrated with cell cycle progression. It could also control both cell size and morphogenesis, thereby reconciling divergent models for mitotic checkpoint function.
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Affiliation(s)
- Steph D Anastasia
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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27
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Lajoie P, Moir RD, Willis IM, Snapp EL. Kar2p availability defines distinct forms of endoplasmic reticulum stress in living cells. Mol Biol Cell 2012; 23:955-64. [PMID: 22219379 PMCID: PMC3290652 DOI: 10.1091/mbc.e11-12-0995] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The endoplasmic reticulum (ER) unfolded protein response (UPR) is correlated with changes in unfolded secretory levels. A novel fluorescence biosensor now reports changes in the unfolded protein burden. This reporter reveals a form of ER stress—inositol withdrawal—that stimulates the UPR without changes in unfolded protein levels. Accumulation of misfolded secretory proteins in the endoplasmic reticulum (ER) activates the unfolded protein response (UPR) stress pathway. To enhance secretory protein folding and promote adaptation to stress, the UPR upregulates ER chaperone levels, including BiP. Here we describe chromosomal tagging of KAR2, the yeast homologue of BiP, with superfolder green fluorescent protein (sfGFP) to create a multifunctional endogenous reporter of the ER folding environment. Changes in Kar2p-sfGFP fluorescence levels directly correlate with UPR activity and represent a robust reporter for high-throughput analysis. A novel second feature of this reporter is that photobleaching microscopy (fluorescence recovery after photobleaching) of Kar2p-sfGFP mobility reports on the levels of unfolded secretory proteins in individual cells, independent of UPR status. Kar2p-sfGFP mobility decreases upon treatment with tunicamycin or dithiothreitol, consistent with increased levels of unfolded proteins and the incorporation of Kar2p-sfGFP into slower-diffusing complexes. During adaptation, we observe a significant lag between down-regulation of the UPR and resolution of the unfolded protein burden. Finally, we find that Kar2p-sfGFP mobility significantly increases upon inositol withdrawal, which also activates the UPR, apparently independent of unfolded protein levels. Thus Kar2p mobility represents a powerful new tool capable of distinguishing between the different mechanisms leading to UPR activation in living cells.
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Affiliation(s)
- Patrick Lajoie
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY 10461, USA
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28
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Sebastian TT, Baldridge RD, Xu P, Graham TR. Phospholipid flippases: building asymmetric membranes and transport vesicles. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:1068-77. [PMID: 22234261 DOI: 10.1016/j.bbalip.2011.12.007] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 12/14/2011] [Accepted: 12/16/2011] [Indexed: 01/25/2023]
Abstract
Phospholipid flippases in the type IV P-type ATPase family (P4-ATPases) are essential components of the Golgi, plasma membrane and endosomal system that play critical roles in membrane biogenesis. These pumps flip phospholipid across the bilayer to create an asymmetric membrane structure with substrate phospholipids, such as phosphatidylserine and phosphatidylethanolamine, enriched within the cytosolic leaflet. The P4-ATPases also help form transport vesicles that bud from Golgi and endosomal membranes, thereby impacting the sorting and localization of many different proteins in the secretory and endocytic pathways. At the organismal level, P4-ATPase deficiencies are linked to liver disease, obesity, diabetes, hearing loss, neurological deficits, immune deficiency and reduced fertility. Here, we review the biochemical, cellular and physiological functions of P4-ATPases, with an emphasis on their roles in vesicle-mediated protein transport. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Tessy T Sebastian
- Department of Biological Sciences, Vanderbilt University, Nashville TN 37235, USA
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Baumann K, Adelantado N, Lang C, Mattanovich D, Ferrer P. Protein trafficking, ergosterol biosynthesis and membrane physics impact recombinant protein secretion in Pichia pastoris. Microb Cell Fact 2011; 10:93. [PMID: 22050768 PMCID: PMC3219557 DOI: 10.1186/1475-2859-10-93] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 11/03/2011] [Indexed: 12/27/2022] Open
Abstract
Background The increasing availability of 'omics' databases provide important platforms for yeast engineering strategies since they offer a lot of information on the physiology of the cells under diverse growth conditions, including environmental stresses. Notably, only a few of these approaches have considered a performance under recombinant protein production conditions. Recently, we have identified a beneficial effect of low oxygen availability on the expression of a human Fab fragment in Pichia pastoris. Transcriptional analysis and data mining allowed for the selection of potential targets for strain improvement. A first selection of these candidates has been evaluated as recombinant protein secretion enhancers. Results Based on previous transcriptomics analyses, we selected 8 genes for co-expression in the P. pastoris strain already secreting a recombinant Fab fragment. Notably, WSC4 (which is involved in trafficking through the ER) has been identified as a novel potential target gene for strain improvement, with up to a 1.2-fold increase of product yield in shake flask cultures. A further transcriptomics-based strategy to modify the yeast secretion system was focused on the ergosterol pathway, an aerobic process strongly affected by oxygen depletion. By specifically partially inhibiting ergosterol synthesis with the antifungal agent fluconazole (inhibiting Erg11p), we tried to mimic the hypoxic conditions, in which the cellular ergosterol content was significantly decreased. This strategy led to an improved Fab yield (2-fold) without impairing cellular growth. Since ergosterol shortage provokes alterations in the plasma membrane composition, an important role of this cellular structure in protein secretion is suggested. This hypothesis was additionally supported by the fact that the addition of non-ionic surfactants also enhanced Fab secretion. Conclusions The current study presents a systems biotechnology-based strategy for the engineering of the industrially important yeast P. pastoris combining the use of host specific DNA microarray technologies and physiological studies under well defined environmental conditions. Such studies allowed for the identification of novel targets related with protein trafficking and ergosterol biosynthesis for improved recombinant protein production. Nevertheless, further studies will be required to elucidate the precise mechanisms whereby membrane biogenesis and composition impact on protein secretion in P. pastoris.
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Affiliation(s)
- Kristin Baumann
- Department of Chemical Engineering, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
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30
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Mitjana FV, Petkova MI, Pujol-Carrion N, de la Torre-Ruiz MA. Pkc1 and actin polymerisation activities play a role in ribosomal gene repression associated with secretion impairment caused by oxidative stress. FEMS Yeast Res 2011; 11:656-9. [PMID: 22093750 DOI: 10.1111/j.1567-1364.2011.00754.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 06/20/2011] [Accepted: 08/18/2011] [Indexed: 11/29/2022] Open
Abstract
In Saccharomyces cerevisiae, the cell integrity pathway plays a role in the oxidative stress response. In this study, we show that the Pkc1 protein mediates oxidative signalling by helping to downregulate ribosomal gene expression when cells are exposed to hydrogen peroxide. An active actin cytoskeleton is required for this function, because the cells blocked in actin polymerisation were unable to repress ribosomal gene transcription. Following the invertase secretion pattern, we hypothesize that oxidative stress induced by hydrogen peroxide could have affected the latter steps of secretion. This would explain why the Pkc1 function was required to repress ribosomal biogenesis.
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31
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Dumay-Odelot H, Durrieu-Gaillard S, Da Silva D, Roeder RG, Teichmann M. Cell growth- and differentiation-dependent regulation of RNA polymerase III transcription. Cell Cycle 2010; 9:3687-99. [PMID: 20890107 DOI: 10.4161/cc.9.18.13203] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
RNA polymerase III transcribes small untranslated RNAs that fulfill essential cellular functions in regulating transcription, RNA processing, translation and protein translocation. RNA polymerase III transcription activity is tightly regulated during the cell cycle and coupled to growth control mechanisms. Furthermore, there are reports of changes in RNA polymerase III transcription activity during cellular differentiation, including the discovery of a novel isoform of human RNA polymerase III that has been shown to be specifically expressed in undifferentiated human H1 embryonic stem cells. Here, we review major regulatory mechanisms of RNA polymerase III transcription during the cell cycle, cell growth and cell differentiation.
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Affiliation(s)
- Hélène Dumay-Odelot
- Institut Européen de Chimie et Biologie (I.E.C.B.), Université de Bordeaux, Institut National de la Santé et de la Recherche Médicale (INSERM) U869, Pessac, France
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32
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Ash MR, Faelber K, Kosslick D, Albert GI, Roske Y, Kofler M, Schuemann M, Krause E, Freund C. Conserved β-Hairpin Recognition by the GYF Domains of Smy2 and GIGYF2 in mRNA Surveillance and Vesicular Transport Complexes. Structure 2010; 18:944-54. [PMID: 20696395 DOI: 10.1016/j.str.2010.04.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 04/09/2010] [Accepted: 04/28/2010] [Indexed: 01/07/2023]
Affiliation(s)
- Miriam-Rose Ash
- Protein Engineering, Leibniz-Institut fuer Molekulare Pharmakologie, 13125 Berlin, Germany
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33
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Goranov AI, Amon A. Growth and division--not a one-way road. Curr Opin Cell Biol 2010; 22:795-800. [PMID: 20667436 DOI: 10.1016/j.ceb.2010.06.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Accepted: 06/29/2010] [Indexed: 01/31/2023]
Abstract
Maintaining cell size homeostasis and regulating cell size in response to changing conditions is a fundamental property of organisms. Here we examine the recent advances in our understanding of the interplay between accumulation of mass (growth) and the progression through the cell cycle (proliferation), the coordination of which determines the size of cells. It is well established that growth affects cell division (reviewed in Jorgensen and Tyers, 2004). This review will focus on the reverse, less well-defined relationship-how cell cycle progression affects growth. We will summarize findings that indicate that growth is not constant during the cell cycle and discuss the surprising possibility that cyclin-dependent kinases (CDKs) inhibit growth.
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Affiliation(s)
- Alexi I Goranov
- David H. Koch Institute for Integrative Cancer Research and Howard Hughes Medical Institute, Massachusetts Institute of Technology, E17-233, 40 Ames Street, Cambridge, MA 02139, USA
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34
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Rodicio R, Heinisch JJ. Together we are strong-cell wall integrity sensors in yeasts. Yeast 2010; 27:531-40. [DOI: 10.1002/yea.1785] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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35
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An extensive circuitry for cell wall regulation in Candida albicans. PLoS Pathog 2010; 6:e1000752. [PMID: 20140194 PMCID: PMC2816693 DOI: 10.1371/journal.ppat.1000752] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Accepted: 01/06/2010] [Indexed: 01/30/2023] Open
Abstract
Protein kinases play key roles in signaling and response to changes in the external environment. The ability of Candida albicans to quickly sense and respond to changes in its environment is key to its survival in the human host. Our guiding hypothesis was that creating and screening a set of protein kinase mutant strains would reveal signaling pathways that mediate stress response in C. albicans. A library of protein kinase mutant strains was created and screened for sensitivity to a variety of stresses. For the majority of stresses tested, stress response was largely conserved between C. albicans, Saccharomyces cerevisiae, and Schizosaccharomyces pombe. However, we identified eight protein kinases whose roles in cell wall regulation (CWR) were not expected from functions of their orthologs in the model fungi Saccharomyces cerevisiae and Schizosaccharomyces pombe. Analysis of the conserved roles of these protein kinases indicates that establishment of cell polarity is critical for CWR. In addition, we found that septins, crucial to budding, are both important for surviving and are mislocalized by cell wall stress. Our study shows an expanded role for protein kinase signaling in C. albicans cell wall integrity. Our studies suggest that in some cases, this expansion represents a greater importance for certain pathways in cell wall biogenesis. In other cases, it appears that signaling pathways have been rewired for a cell wall integrity response. Candida albicans is the major fungal commensal and pathogen of humans. Like most microorganisms, C. albicans is surrounded and protected by a cell wall. This cell wall has two purposes: to act as a rigid “exoskeleton” to prevent cells from bursting, and to provide a surface where a cell can interact with the outside environment while protecting the cell itself from this environment. Maintenance of this structure has been well studied in the model fungus, Saccharomyces cerevisiae, but previous evidence suggested that C. albicans might have additional inputs to this process. By creating and testing a library of mutant strains for sensitivity to cell wall stress, we were able to identify a number of conserved genes with roles in this process not shared by their S. cerevisiae counterparts. Although some of these genes had previously been linked to cell wall integrity, it appears that they have increased impact on this process in C. albicans. For other genes, their role in cell wall integrity may represent a novel connection. Our findings provide insight into novel aspects of cell wall integrity in this pathogen and lay a foundation for its more detailed analysis.
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36
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Singh J, Tyers M. A Rab escort protein integrates the secretion system with TOR signaling and ribosome biogenesis. Genes Dev 2009; 23:1944-58. [PMID: 19684114 DOI: 10.1101/gad.1804409] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The coupling of environmental conditions to cell growth and division is integral to cell fitness. In Saccharomyces cerevisiae, the transcription factor Sfp1 couples nutrient status to cell growth rate by controlling the expression of ribosome biogenesis (Ribi) and ribosomal protein (RP) genes. Sfp1 is localized to the nucleus in rich nutrients, but upon nutrient limitation or target of rapamycin (TOR) pathway inhibition by rapamycin, Sfp1 rapidly exits the nucleus, leading to repression of the Ribi/RP regulons. Through systematic cell-based screens we found that many components of the secretory system influence Sfp1 localization. Notably, the essential Rab escort protein Mrs6 exhibited a nutrient-sensitive interaction with Sfp1. Overexpression of Mrs6 prevented nuclear localization of Sfp1 in rich nutrients, whereas loss of Mrs6 resulted in nuclear Sfp1 localization in poor nutrients. These effects were specific to Sfp1 and independent of the protein kinase C (PKC) pathway, suggesting that Mrs6 lies in a distinct branch of TOR and ribosome biogenesis regulation. Rapamycin-resistant alleles of MRS6 were defective in the cytoplasmic retention of Sfp1, the control of cell size, and in the repression of the Ribi/RP regulons. The Sfp1-Mrs6 interaction is a nexus for growth regulation that links the secretory system and TOR-dependent nutrient signaling to ribosome biogenesis.
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Affiliation(s)
- Jaspal Singh
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
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37
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Wei Y, Tsang CK, Zheng XFS. Mechanisms of regulation of RNA polymerase III-dependent transcription by TORC1. EMBO J 2009; 28:2220-30. [PMID: 19574957 DOI: 10.1038/emboj.2009.179] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/29/2009] [Indexed: 12/27/2022] Open
Abstract
We have found earlier that Tor1 binds to 5S rDNA chromatin but the functional significance has not been established. Here, we show that association with 5S rDNA chromatin is necessary for TOR complex 1 (TORC1) to regulate the synthesis of 5S ribosomal RNA and transfer RNAs (tRNAs) by RNA polymerase (Pol) III, as well as the phosphorylation and binding to Pol III-transcribed genes of the Pol III repressor Maf1. Interestingly, TORC1 does not bind to tRNA genes, suggesting that TORC1 modulates tRNA synthesis indirectly through Maf1 phosphorylation at the rDNA loci. We also find that Maf1 cytoplasmic localization is dependent on the SSD1-v allele. In W303 cells that carry the SSD1-d allele, Maf1 is constitutively nuclear but its nucleolar localization is inhibited by TORC1, indicating that TORC1 regulates nucleoplasm-to-nucleolus transport of Maf1. Finally, we show that TORC1 interacts with Maf1 in vivo and phosphorylates Maf1 in vitro, and regulates Maf1 nucleoplasm-to-nucleolus translocation. Together, these observations provide new insights into the chromatin-dependent mechanism by which TORC1 controls transcription by Pol III.
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Affiliation(s)
- Yuehua Wei
- Graduate Program in Cellular and Molecular Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ, USA
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38
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Soragni E, Kassavetis GA. Absolute gene occupancies by RNA polymerase III, TFIIIB, and TFIIIC in Saccharomyces cerevisiae. J Biol Chem 2008; 283:26568-76. [PMID: 18667429 PMCID: PMC2546553 DOI: 10.1074/jbc.m803769200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/16/2008] [Indexed: 11/06/2022] Open
Abstract
A major limitation of chromatin immunoprecipitation lies in the challenge of measuring the immunoprecipitation effectiveness of different proteins and antibodies and the resultant inability to compare the occupancies of different DNA-binding proteins. Here we present the implementation of a quantitative chromatin immunoprecipitation assay in the RNA polymerase III (pol III) system that allowed us to measure the absolute in vivo occupancy of pol III and its two transcription factors, TFIIIC and TFIIIB, on a subset of pol III genes. The crucial point of our analysis was devising a method that allows the accurate determination of the immunoprecipitation efficiency for each protein. We achieved this by spiking every immunoprecipitation reaction with the formaldehyde cross-linked in vitro counterparts of TFIIIB-, TFIIIC-, and pol III-DNA complexes, measuring the in vitro occupancies of the corresponding factors on a DNA probe and determining probe recovery by quantitative PCR. Analysis of nine pol III-transcribed genes with diverse sequence characteristics showed a very high occupancy by TFIIIB and pol III (pol III occupancy being generally approximately 70% of TFIIIB occupancy) and a TFIIIC occupancy that ranged between approximately 5 and 25%. Current data suggest that TFIIIC is released during transcription in vitro, and it has been proposed that TFIIIB suffices for pol III recruitment in vivo. Our findings point to the transient nature of the TFIIIC-DNA interaction in vivo, with no significant counter-correlation between pol III and TFIIIC occupancy and instead to a dependence of TFIIIB-DNA and TFIIIC-DNA complex maintenance in vivo on pol III function.
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Affiliation(s)
- Elisabetta Soragni
- Division of Biological Sciences and Center for Molecular Genetics,
University of California, San Diego, La Jolla, California 92093-0634
| | - George A. Kassavetis
- Division of Biological Sciences and Center for Molecular Genetics,
University of California, San Diego, La Jolla, California 92093-0634
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39
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Disrupting vesicular trafficking at the endosome attenuates transcriptional activation by Gcn4. Mol Cell Biol 2008; 28:6796-818. [PMID: 18794364 DOI: 10.1128/mcb.00800-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The late endosome (MVB) plays a key role in coordinating vesicular transport of proteins between the Golgi complex, vacuole/lysosome, and plasma membrane. We found that deleting multiple genes involved in vesicle fusion at the MVB (class C/D vps mutations) impairs transcriptional activation by Gcn4, a global regulator of amino acid biosynthetic genes, by decreasing the ability of chromatin-bound Gcn4 to stimulate preinitiation complex assembly at the promoter. The functions of hybrid activators with Gal4 or VP16 activation domains are diminished in class D mutants as well, suggesting a broader defect in activation. Class E vps mutations, which impair protein sorting at the MVB, also decrease activation by Gcn4, provided they elicit rapid proteolysis of MVB cargo proteins in the aberrant late endosome. By contrast, specifically impairing endocytic trafficking from the plasma membrane, or vesicular transport to the vacuole, has a smaller effect on Gcn4 function. Thus, it appears that decreasing cargo proteins in the MVB through impaired delivery or enhanced degradation, and not merely the failure to transport cargo properly to the vacuole or downregulate plasma membrane proteins by endocytosis, is required to attenuate substantially transcriptional activation by Gcn4.
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40
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Acker J, Ozanne C, Kachouri-Lafond R, Gaillardin C, Neuvéglise C, Marck C. Dicistronic tRNA-5S rRNA genes in Yarrowia lipolytica: an alternative TFIIIA-independent way for expression of 5S rRNA genes. Nucleic Acids Res 2008; 36:5832-44. [PMID: 18790808 PMCID: PMC2566860 DOI: 10.1093/nar/gkn549] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In eukaryotes, genes transcribed by RNA polymerase III (Pol III) carry their own internal promoters and as such, are transcribed as individual units. Indeed, a very few cases of dicistronic Pol III genes are yet known. In contrast to other hemiascomycetes, 5S rRNA genes of Yarrowia lipolytica are not embedded into the tandemly repeated rDNA units, but appear scattered throughout the genome. We report here an unprecedented genomic organization: 48 over the 108 copies of the 5S rRNA genes are located 3' of tRNA genes. We show that these peculiar tRNA-5S rRNA dicistronic genes are expressed in vitro and in vivo as Pol III transcriptional fusions without the need of the 5S rRNA gene-specific factor TFIIIA, the deletion of which displays a viable phenotype. We also report the existence of a novel putative non-coding Pol III RNA of unknown function about 70 nucleotide-long (RUF70), the 13 genes of which are devoid of internal Pol III promoters and located 3' of the 13 copies of the tDNA-Trp (CCA). All genes embedded in the various dicistronic genes, fused 5S rRNA genes, RUF70 genes and their leader tRNA genes appear to be efficiently transcribed and their products correctly processed in vivo.
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Affiliation(s)
- Joël Acker
- Saclay Biology and Technologies Institute (iBiTec-S), CEA, 91191 Gif-sur-Yvette Cedex, France
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41
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Hos2p/Set3p deacetylase complex signals secretory stress through the Mpk1p cell integrity pathway. EUKARYOTIC CELL 2008; 7:1191-9. [PMID: 18487345 DOI: 10.1128/ec.00059-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Perturbations in secretory function activate stress response pathways critical for yeast survival. Here we report the identification of the Hos2p/Set3p deacetylase complex (SET3C) as an essential component of the secretory stress response. Strains lacking core components of the Hos2p/Set3p complex exhibit hypersensitivity to secretory stress. Although not required for the unfolded protein response (UPR) and ribosomal gene repression, the Hos2p complex is required for proper activation of the Mpk1p/Slt2p cell integrity kinase cascade. Disruption of the Hos2p complex results in abrogated Mpk1p phosphorylation, whereas constitutive activation of the Mpk1p pathway rescues the hos2Delta mutant growth defect in response to secretory stress. Furthermore, Hos2p activity is required for the Mpk1p-mediated activation of stress-responsive transcription factor Rlm1p, but not for the stress-induced degradation of the C-type cyclin Ssn8p. Our results identify the Hos2p complex as a critical component of the secretory stress response and support the existence a coordinated stress response consisting of the UPR, ribosomal gene repression, and mitogen-activated protein kinase signaling in response to defects in secretory function.
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42
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Towpik J, Graczyk D, Gajda A, Lefebvre O, Boguta M. Derepression of RNA polymerase III transcription by phosphorylation and nuclear export of its negative regulator, Maf1. J Biol Chem 2008; 283:17168-74. [PMID: 18445601 DOI: 10.1074/jbc.m709157200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Maf1 is the global repressor of RNA polymerase III (Pol III) in yeast Saccharomyces cerevisiae. Transcription regulation by Maf1 is important under stress conditions and during the switch between fermentation and respiration. Under repressive conditions on nonfermentable carbon sources, Maf1 is dephosphorylated and located predominantly in the nucleus. When cells were shifted to glucose medium, Maf1 became phosphorylated and concomitantly relocated to the cytoplasm. This relocation was dependent on Msn5, a carrier responsible for export of several other phosphoproteins out of the nucleus. Using coimmunoprecipitation, Maf1 was found to interact with Msn5. When msn5-Delta cells were transferred to glucose, Maf1 remained in the nucleus. Remarkably, despite constitutive presence in the nucleus, Maf1 was dephosphorylated and phosphorylated normally in the msn5-Delta mutant, and Pol III was under proper regulation. That phosphorylation of Maf1 and Pol III derepression are tightly linked was shown by studying tRNA transcription in Maf1 mutants with an altered pattern of phosphorylation. In summary, we conclude that phosphorylation of Maf1 inside the nucleus acts both directly by decreasing of Maf1-mediated repression of Pol III and indirectly by stimulation of Msn5 binding and export of nuclear Maf1 to the cytoplasm.
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Affiliation(s)
- Joanna Towpik
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawiñskiego 5a, 02-106 Warsaw, Poland
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43
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Georgiev A, Leipus A, Olsson I, Berrez JM, Mutvei A. Characterization of MYR1, a dosage suppressor of YPT6 and RIC1 deficient mutants. Curr Genet 2008; 53:235-47. [PMID: 18327588 DOI: 10.1007/s00294-008-0183-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2007] [Revised: 02/20/2008] [Accepted: 02/25/2008] [Indexed: 02/03/2023]
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Cieśla M, Towpik J, Graczyk D, Oficjalska-Pham D, Harismendy O, Suleau A, Balicki K, Conesa C, Lefebvre O, Boguta M. Maf1 is involved in coupling carbon metabolism to RNA polymerase III transcription. Mol Cell Biol 2007; 27:7693-702. [PMID: 17785443 PMCID: PMC2169064 DOI: 10.1128/mcb.01051-07] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 07/04/2007] [Accepted: 08/23/2007] [Indexed: 12/29/2022] Open
Abstract
RNA polymerase III (Pol III) produces essential components of the biosynthetic machinery, and therefore its activity is tightly coupled with cell growth and metabolism. In the yeast Saccharomyces cerevisiae, Maf1 is the only known global and direct Pol III transcription repressor which mediates numerous stress signals. Here we demonstrate that transcription regulation by Maf1 is not limited to stress but is important for the switch between fermentation and respiration. Under respiratory conditions, Maf1 is activated by dephosphorylation and imported into the nucleus. The transition from a nonfermentable carbon source to that of glucose induces Maf1 phosphorylation and its relocation to the cytoplasm. The absence of Maf1-mediated control of tRNA synthesis impairs cell viability in nonfermentable carbon sources. The respiratory phenotype of maf1-Delta allowed genetic suppression studies to dissect the mechanism of Maf1 action on the Pol III transcription apparatus. Moreover, in cells grown in a nonfermentable carbon source, Maf1 regulates the levels of different tRNAs to various extents. The differences in regulation may contribute to the physiological role of Maf1.
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Affiliation(s)
- Małgorzata Cieśla
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
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45
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Piao HL, Machado IM, Payne GS. NPFXD-mediated endocytosis is required for polarity and function of a yeast cell wall stress sensor. Mol Biol Cell 2006; 18:57-65. [PMID: 17065552 PMCID: PMC1751320 DOI: 10.1091/mbc.e06-08-0721] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The actin-associated protein Sla1p, through its SHD1 domain, acts as an adaptor for the NPFX(1,2)D endocytic targeting signal in yeast. Here we report that Wsc1p, a cell wall stress sensor, depends on this signal-adaptor pair for endocytosis. Mutation of NPFDD in Wsc1p or expression of Sla1p lacking SHD1 blocked Wsc1p internalization. By live cell imaging, endocytically defective Wsc1p was not concentrated at sites of endocytosis. Polarized distribution of Wsc1p to regions of cell growth was lost in the absence of endocytosis. Mutations in genes necessary for endosome to Golgi traffic caused redistribution of Wsc1p from the cell surface to internal compartments, indicative of recycling. Inhibition of Wsc1p endocytosis caused defects in polarized deposition of the cell wall and increased sensitivity to perturbation of cell wall synthesis. Our results reveal that the NPFX(1,2)D-Sla1p system is responsible for directing Wsc1p into an endocytosis and recycling pathway necessary to maintain yeast cell wall polarity. The dynamic localization of Wsc1p, a sensor of the extracellular wall in yeast, resembles polarized distribution of certain extracellular matrix-sensing integrins through endocytic recycling.
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Affiliation(s)
- Hai Lan Piao
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095
| | - Iara M.P. Machado
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095
| | - Gregory S. Payne
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095
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46
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Moir RD, Lee J, Haeusler RA, Desai N, Engelke DR, Willis IM. Protein kinase A regulates RNA polymerase III transcription through the nuclear localization of Maf1. Proc Natl Acad Sci U S A 2006; 103:15044-9. [PMID: 17005718 PMCID: PMC1622776 DOI: 10.1073/pnas.0607129103] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Maf1 is an essential and specific mediator of transcriptional repression in the RNA polymerase (pol) III system. Maf1-dependent repression occurs in response to a wide range of conditions, suggesting that the protein itself is targeted by the major nutritional and stress-signaling pathways. We show that Maf1 is a substrate for cAMP-dependent PKA in vitro and is differentially phosphorylated on PKA sites in vivo under normal versus repressing conditions. PKA activity negatively regulates Maf1 function because strains with unregulated high PKA activity block repression of pol III transcription in vivo, and strains lacking all PKA activity are hyperrepressible. Nuclear accumulation of Maf1 is required for transcriptional repression and is regulated by two nuclear localization sequences in the protein. An analysis of PKA phosphosite mutants shows that the localization of Maf1 is affected via the N-terminal nuclear localization sequence. In particular, mutations that prevent phosphorylation at PKA consensus sites promote nuclear accumulation of Maf1 without inducing repression. These results indicate that negative regulation of Maf1 by PKA is achieved by inhibiting its nuclear import and suggest that a PKA-independent activation step is required for nuclear Maf1 to function in the repression of pol III transcription. Finally, we report a previously undescribed phenotype for Maf1 in tRNA gene-mediated silencing of nearby RNA pol II transcription.
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Affiliation(s)
- Robyn D. Moir
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461; and
| | - JaeHoon Lee
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461; and
| | - Rebecca A. Haeusler
- Department of Biological Chemistry, University of Michigan Medical School, 3200 MSRB III, Ann Arbor, MI 48109-0606
| | - Neelam Desai
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461; and
| | - David R. Engelke
- Department of Biological Chemistry, University of Michigan Medical School, 3200 MSRB III, Ann Arbor, MI 48109-0606
| | - Ian M. Willis
- *Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461; and
- To whom correspondence should be addressed. E-mail:
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Laferté A, Favry E, Sentenac A, Riva M, Carles C, Chédin S. The transcriptional activity of RNA polymerase I is a key determinant for the level of all ribosome components. Genes Dev 2006; 20:2030-40. [PMID: 16882981 PMCID: PMC1536055 DOI: 10.1101/gad.386106] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Regulation of ribosome biogenesis is a key element of cell biology, not only because ribosomes are directly required for growth, but also because ribosome production monopolizes nearly 80% of the global transcriptional activity in rapidly growing yeast cells. These observations underscore the need for a tight regulation of ribosome synthesis in response to environmental conditions. In eukaryotic cells, ribosome synthesis involves the activities of the three nuclear RNA polymerases (Pol). Although postulated, there is no clear evidence indicating whether the maintenance of an equimolar supply of ribosomal components reflects communication between the nuclear transcriptional machineries. Here, by constructing a yeast strain expressing a Pol I that remains constitutively competent for the initiation of transcription under stress conditions, we demonstrate that derepression of Pol I transcription leads to a derepression of Pol II transcription that is restricted to the genes encoding ribosomal proteins. Furthermore, we show that the level of 5S rRNA, synthesized by Pol III, is deregulated concomitantly with Pol I transcription. Altogether, these results indicate that a partial derepression of Pol I activity drives an abnormal accumulation of all ribosomal components, highlighting the critical role of the regulation of Pol I activity within the control of ribosome biogenesis.
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Affiliation(s)
- Arnaud Laferté
- Laboratoire de Transcription des Gènes, Service de Biochimie et de Génétique Moléculaire, CEA/Saclay, F-Gif sur Yvette, France
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48
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Chen S, Wang J, Muthusamy BP, Liu K, Zare S, Andersen RJ, Graham TR. Roles for the Drs2p-Cdc50p Complex in Protein Transport and Phosphatidylserine Asymmetry of the Yeast Plasma Membrane. Traffic 2006; 7:1503-17. [PMID: 16956384 DOI: 10.1111/j.1600-0854.2006.00485.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Drs2p, a P-type adenosine triphosphatase required for a phosphatidylserine (PS) flippase activity in the yeast trans Golgi network (TGN), was first implicated in protein trafficking by a screen for mutations synthetically lethal with arf1 (swa). Here, we show that SWA4 is allelic to CDC50, encoding a membrane protein previously shown to chaperone Drs2p from the endoplasmic reticulum to the Golgi complex. We find that cdc50Delta exhibits the same clathrin-deficient phenotypes as drs2Delta, including delayed transport of carboxypeptidase Y to the vacuole, mislocalization of resident TGN enzymes and the accumulation of aberrant membrane structures. These trafficking defects precede appearance of cell polarity defects in cdc50Delta, suggesting that the latter are a secondary consequence of disrupting Golgi function. Involvement of Drs2p-Cdc50p in PS translocation suggests a role in restricting PS to the cytosolic leaflet of the Golgi and plasma membrane. Annexin V binding and papuamide B hypersensitivity indicate that drs2Delta or cdc50Delta causes a loss of plasma membrane PS asymmetry. However, clathrin and other endocytosis null mutants also exhibit a comparable loss of PS asymmetry, and studies with drs2-ts and clathrin (chc1-ts) conditional mutants suggest that loss of plasma membrane asymmetry is a secondary consequence of disrupting protein trafficking.
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Affiliation(s)
- Sophie Chen
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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49
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Roberts DN, Wilson B, Huff JT, Stewart AJ, Cairns BR. Dephosphorylation and genome-wide association of Maf1 with Pol III-transcribed genes during repression. Mol Cell 2006; 22:633-44. [PMID: 16762836 PMCID: PMC2788557 DOI: 10.1016/j.molcel.2006.04.009] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Revised: 01/30/2006] [Accepted: 04/05/2006] [Indexed: 11/23/2022]
Abstract
Nutrient deprivation and various stress conditions repress RNA polymerase III (Pol III) transcription in S. cerevisiae. The signaling pathways that relay stress and nutrient conditions converge on the conserved protein Maf1, but how Maf1 integrates environmental conditions and couples them to transcriptional repression is largely unknown. Here, we demonstrate that Maf1 is phosphorylated in favorable conditions, whereas diverse unfavorable conditions lead to rapid Maf1 dephosphorylation, nuclear localization, physical association of dephosphorylated Maf1 with Pol III, and Maf1 targeting to Pol III-transcribed genes genome wide. Furthermore, Maf1 mutants defective in full dephosphorylation display maf1Delta phenotypes and are compromised for both nuclear localization and Pol III association. Repression conditions also promote TFIIIB-TFIIIC interactions in crosslinked chromatin. Taken together, Maf1 appears to integrate environmental conditions and signaling pathways through its phosphorylation state, with stress leading to dephosphorylation, association with Pol III at target loci, alterations in basal factor interactions, and transcriptional repression.
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Affiliation(s)
- Douglas N. Roberts
- Howard Hughes Medical Institute
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Boris Wilson
- Howard Hughes Medical Institute
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Jason T. Huff
- Howard Hughes Medical Institute
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Allen J. Stewart
- Howard Hughes Medical Institute
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Bradley R. Cairns
- Howard Hughes Medical Institute
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112
- Correspondence:
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50
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Chatterjee I, Gross SR, Kinzy TG, Chen KY. Rapid depletion of mutant eukaryotic initiation factor 5A at restrictive temperature reveals connections to actin cytoskeleton and cell cycle progression. Mol Genet Genomics 2006; 275:264-76. [PMID: 16408210 DOI: 10.1007/s00438-005-0086-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 11/24/2005] [Indexed: 11/29/2022]
Abstract
Eukaryotic initiation factor 5A (eIF5A) is the only protein in nature that contains hypusine, an unusual amino acid derived from the modification of lysine by spermidine. Two genes, TIF51A and TIF51B, encode eIF5A in the yeast Saccharomyces cerevisiae. In an effort to understand the structure-function relationship of eIF5A, we have generated yeast mutants by introducing plasmid-borne tif51A into a double null strain where both TIF51A and TIF51B have been disrupted. One of the mutants, tsL102A strain (tif51A L102A tif51aDelta tif51bDelta) exhibits a strong temperature-sensitive growth phenotype. At the restrictive temperature, tsL102A strain also exhibits a cell shape change, a lack of volume change in response to temperature increase and becomes more sensitive to ethanol, a hallmark of defects in the PKC/WSC cell wall integrity pathway. In addition, a striking change in actin dynamics and a complete cell cycle arrest at G1 phase occur in tsL102A cells at restrictive temperature. The temperature-sensitivity of tsL102A strain is due to a rapid loss of mutant eIF5A with the half-life reduced from 6 h at permissive temperature to 20 min at restrictive temperature. Phenylmethyl sulfonylfluoride (PMSF), an irreversible inhibitor of serine protease, inhibited the degradation of mutant eIF5A and suppressed the temperature-sensitive growth arrest. Sorbitol, an osmotic stabilizer that complement defects in PKC/WSC pathways, stabilizes the mutant eIF5A and suppresses all the observed temperature-sensitive phenotypes.
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Affiliation(s)
- Ishita Chatterjee
- Department of Chemistry and Chemical Biology, Rutgers-The State University of New Jersey, Piscataway, NJ 08854-8087, USA
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