201
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Atias N, Kupiec M, Sharan R. Systematic identification and correction of annotation errors in the genetic interaction map of Saccharomyces cerevisiae. Nucleic Acids Res 2015; 44:e50. [PMID: 26602688 PMCID: PMC4797274 DOI: 10.1093/nar/gkv1284] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/04/2015] [Indexed: 01/05/2023] Open
Abstract
The yeast mutant collections are a fundamental tool in deciphering genomic organization and function. Over the last decade, they have been used for the systematic exploration of ∼6 000 000 double gene mutants, identifying and cataloging genetic interactions among them. Here we studied the extent to which these data are prone to neighboring gene effects (NGEs), a phenomenon by which the deletion of a gene affects the expression of adjacent genes along the genome. Analyzing ∼90,000 negative genetic interactions observed to date, we found that more than 10% of them are incorrectly annotated due to NGEs. We developed a novel algorithm, GINGER, to identify and correct erroneous interaction annotations. We validated the algorithm using a comparative analysis of interactions from Schizosaccharomyces pombe. We further showed that our predictions are significantly more concordant with diverse biological data compared to their mis-annotated counterparts. Our work uncovered about 9500 new genetic interactions in yeast.
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Affiliation(s)
- Nir Atias
- Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Roded Sharan
- Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
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202
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Zhu J, Deng S, Lu P, Bu W, Li T, Yu L, Xie Z. The Ccl1-Kin28 kinase complex regulates autophagy under nitrogen starvation. J Cell Sci 2015; 129:135-44. [PMID: 26567215 DOI: 10.1242/jcs.177071] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 11/06/2015] [Indexed: 01/15/2023] Open
Abstract
Starvation triggers global alterations in the synthesis and turnover of proteins. Under such conditions, the recycling of essential nutrients by using autophagy is indispensable for survival. By screening known kinases in the yeast genome, we newly identified a regulator of autophagy, the Ccl1-Kin28 kinase complex (the equivalent of the mammalian cyclin-H-Cdk7 complex), which is known to play key roles in RNA-polymerase-II-mediated transcription. We show that inactivation of Ccl1 caused complete block of autophagy. Interestingly, Ccl1 itself was subject to proteasomal degradation, limiting the level of autophagy during prolonged starvation. We present further evidence that the Ccl1-Kin28 complex regulates the expression of Atg29 and Atg31, which is crucial in the assembly of the Atg1 kinase complex. The identification of this previously unknown regulatory pathway sheds new light on the complex signaling network that governs autophagy activity.
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Affiliation(s)
- Jing Zhu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Shuangsheng Deng
- School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Puzhong Lu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Wenting Bu
- Division of Structure Biology & Biochemistry, School of Biological Sciences, Nanyang Technological University, Singapore 138673, Singapore
| | - Tian Li
- School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Li Yu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Zhiping Xie
- Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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203
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Becker JR, Pons C, Nguyen HD, Costanzo M, Boone C, Myers CL, Bielinsky AK. Genetic Interactions Implicating Postreplicative Repair in Okazaki Fragment Processing. PLoS Genet 2015; 11:e1005659. [PMID: 26545110 PMCID: PMC4636136 DOI: 10.1371/journal.pgen.1005659] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/19/2015] [Indexed: 01/28/2023] Open
Abstract
Ubiquitination of the replication clamp proliferating cell nuclear antigen (PCNA) at the conserved residue lysine (K)164 triggers postreplicative repair (PRR) to fill single-stranded gaps that result from stalled DNA polymerases. However, it has remained elusive as to whether cells engage PRR in response to replication defects that do not directly impair DNA synthesis. To experimentally address this question, we performed synthetic genetic array (SGA) analysis with a ubiquitination-deficient K164 to arginine (K164R) mutant of PCNA against a library of S. cerevisiae temperature-sensitive alleles. The SGA signature of the K164R allele showed a striking correlation with profiles of mutants deficient in various aspects of lagging strand replication, including rad27Δ and elg1Δ. Rad27 is the primary flap endonuclease that processes 5' flaps generated during lagging strand replication, whereas Elg1 has been implicated in unloading PCNA from chromatin. We observed chronic ubiquitination of PCNA at K164 in both rad27Δ and elg1Δ mutants. Notably, only rad27Δ cells exhibited a decline in cell viability upon elimination of PRR pathways, whereas elg1Δ mutants were not affected. We further provide evidence that K164 ubiquitination suppresses replication stress resulting from defective flap processing during Okazaki fragment maturation. Accordingly, ablation of PCNA ubiquitination increased S phase checkpoint activation, indicated by hyperphosphorylation of the Rad53 kinase. Furthermore, we demonstrate that alternative flap processing by overexpression of catalytically active exonuclease 1 eliminates PCNA ubiquitination. This suggests a model in which unprocessed flaps may directly participate in PRR signaling. Our findings demonstrate that PCNA ubiquitination at K164 in response to replication stress is not limited to DNA synthesis defects but extends to DNA processing during lagging strand replication.
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Affiliation(s)
- Jordan R. Becker
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Carles Pons
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Hai Dang Nguyen
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Michael Costanzo
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Charles Boone
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Chad L. Myers
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Anja-Katrin Bielinsky
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
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204
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Filteau M, Hamel V, Pouliot MC, Gagnon-Arsenault I, Dubé AK, Landry CR. Evolutionary rescue by compensatory mutations is constrained by genomic and environmental backgrounds. Mol Syst Biol 2015; 11:832. [PMID: 26459777 PMCID: PMC4631203 DOI: 10.15252/msb.20156444] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Since deleterious mutations may be rescued by secondary mutations during evolution, compensatory evolution could identify genetic solutions leading to therapeutic targets. Here, we tested this hypothesis and examined whether these solutions would be universal or would need to be adapted to one's genetic and environmental makeups. We performed experimental evolutionary rescue in a yeast disease model for the Wiskott–Aldrich syndrome in two genetic backgrounds and carbon sources. We found that multiple aspects of the evolutionary rescue outcome depend on the genotype, the environment, or a combination thereof. Specifically, the compensatory mutation rate and type, the molecular rescue mechanism, the genetic target, and the associated fitness cost varied across contexts. The course of compensatory evolution is therefore highly contingent on the initial conditions in which the deleterious mutation occurs. In addition, these results reveal biologically favored therapeutic targets for the Wiskott–Aldrich syndrome, including the target of an unrelated clinically approved drug. Our results experimentally illustrate the importance of epistasis and environmental evolutionary constraints that shape the adaptive landscape and evolutionary rate of molecular networks.
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Affiliation(s)
- Marie Filteau
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
| | - Véronique Hamel
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
| | - Marie-Christine Pouliot
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
| | - Isabelle Gagnon-Arsenault
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
| | - Alexandre K Dubé
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
| | - Christian R Landry
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval, Québec, Qc, Canada
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205
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Imura Y, Molho M, Chuang C, Nagy PD. Cellular Ubc2/Rad6 E2 ubiquitin-conjugating enzyme facilitates tombusvirus replication in yeast and plants. Virology 2015; 484:265-275. [DOI: 10.1016/j.virol.2015.05.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 02/10/2015] [Accepted: 05/15/2015] [Indexed: 10/23/2022]
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206
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Diaz-Muñoz G, Harchar TA, Lai TP, Shen KF, Hopper AK. Requirement of the spindle pole body for targeting and/or tethering proteins to the inner nuclear membrane. Nucleus 2015; 5:352-66. [PMID: 25482124 PMCID: PMC4152349 DOI: 10.4161/nucl.29793] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Appropriate targeting of inner nuclear membrane (INM) proteins is important for nuclear function and architecture. To gain new insights into the mechanism(s) for targeting and/or tethering peripherally associated proteins to the INM, we screened a collection of temperature sensitive S. cerevisiae yeast mutants for defects in INM location of the peripheral protein, Trm1-II-GFP. We uncovered numerous genes encoding components of the Spindle Pole Body (SPB), the yeast centrosome. SPB alterations affect the localization of both an integral (Heh2) and a peripheral INM protein (Trm1-II-GFP), but not a nucleoplasmic protein (Pus1). In wild-type cells Trm1-II-GFP is evenly distributed around the INM, but in SPB mutants, Trm1-II-GFP mislocalizes as a spot(s) near ER-nucleus junctions, perhaps its initial contact site with the nuclear envelope. Employing live cell imaging over time in a microfluidic perfusion system to study protein dynamics, we show that both Trm1-II-GFP INM targeting and maintenance depend upon the SPB. We propose a novel targeting and/or tethering model for a peripherally associated INM protein that combines mechanisms of both integral and soluble nuclear proteins, and describe a role of the SPB in nuclear envelope dynamics that affects this process.
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Affiliation(s)
- Greetchen Diaz-Muñoz
- a Molecular, Cellular and Developmental Biology Interdisciplinary Program; The Ohio State University; Columbus, OH USA
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207
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Abstract
Maintenance of genome integrity is a fundamental requirement of all organisms. To address this, organisms have evolved extremely faithful modes of replication, DNA repair and chromosome segregation to combat the deleterious effects of an unstable genome. Nonetheless, a small amount of genome instability is the driver of evolutionary change and adaptation, and thus a low level of instability is permitted in populations. While defects in genome maintenance almost invariably reduce fitness in the short term, they can create an environment where beneficial mutations are more likely to occur. The importance of this fact is clearest in the development of human cancer, where genome instability is a well-established enabling characteristic of carcinogenesis. This raises the crucial question: what are the cellular pathways that promote genome maintenance and what are their mechanisms? Work in model organisms, in particular the yeast Saccharomyces cerevisiae, has provided the global foundations of genome maintenance mechanisms in eukaryotes. The development of pioneering genomic tools inS. cerevisiae, such as the systematic creation of mutants in all nonessential and essential genes, has enabled whole-genome approaches to identifying genes with roles in genome maintenance. Here, we review the extensive whole-genome approaches taken in yeast, with an emphasis on functional genomic screens, to understand the genetic basis of genome instability, highlighting a range of genetic and cytological screening modalities. By revealing the biological pathways and processes regulating genome integrity, these analyses contribute to the systems-level map of the yeast cell and inform studies of human disease, especially cancer.
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208
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Genetic Networks Required to Coordinate Chromosome Replication by DNA Polymerases α, δ, and ε in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2015; 5:2187-97. [PMID: 26297725 PMCID: PMC4593000 DOI: 10.1534/g3.115.021493] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Three major DNA polymerases replicate the linear eukaryotic chromosomes. DNA polymerase α-primase (Pol α) and DNA polymerase δ (Pol δ) replicate the lagging-strand and Pol α and DNA polymerase ε (Pol ε) the leading-strand. To identify factors affecting coordination of DNA replication, we have performed genome-wide quantitative fitness analyses of budding yeast cells containing defective polymerases. We combined temperature-sensitive mutations affecting the three replicative polymerases, Pol α, Pol δ, and Pol ε with genome-wide collections of null and reduced function mutations. We identify large numbers of genetic interactions that inform about the roles that specific genes play to help Pol α, Pol δ, and Pol ε function. Surprisingly, the overlap between the genetic networks affecting the three DNA polymerases does not represent the majority of the genetic interactions identified. Instead our data support a model for division of labor between the different DNA polymerases during DNA replication. For example, our genetic interaction data are consistent with biochemical data showing that Pol ε is more important to the Pre-Loading complex than either Pol α or Pol δ. We also observed distinct patterns of genetic interactions between leading- and lagging-strand DNA polymerases, with particular genes being important for coupling proliferating cell nuclear antigen loading/unloading (Ctf18, Elg1) with nucleosome assembly (chromatin assembly factor 1, histone regulatory HIR complex). Overall our data reveal specialized genetic networks that affect different aspects of leading- and lagging-strand DNA replication. To help others to engage with these data we have generated two novel, interactive visualization tools, DIXY and Profilyzer.
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209
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Muir A, Roelants FM, Timmons G, Leskoske KL, Thorner J. Down-regulation of TORC2-Ypk1 signaling promotes MAPK-independent survival under hyperosmotic stress. eLife 2015; 4. [PMID: 26274562 PMCID: PMC4552222 DOI: 10.7554/elife.09336] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/13/2015] [Indexed: 01/10/2023] Open
Abstract
In eukaryotes, exposure to hypertonic conditions activates a MAPK (Hog1 in Saccharomyces cerevisiae and ortholog p38 in human cells). In yeast, intracellular glycerol accumulates to counterbalance the high external osmolarity. To prevent glycerol efflux, Hog1 action impedes the function of the aquaglyceroporin Fps1, in part, by displacing channel co-activators (Rgc1/2). However, Fps1 closes upon hyperosmotic shock even in hog1∆ cells, indicating another mechanism to prevent Fps1-mediated glycerol efflux. In our prior proteome-wide screen, Fps1 was identified as a target of TORC2-dependent protein kinase Ypk1 (Muir et al., 2014). We show here that Fps1 is an authentic Ypk1 substrate and that the open channel state of Fps1 requires phosphorylation by Ypk1. Moreover, hyperosmotic conditions block TORC2-dependent Ypk1-mediated Fps1 phosphorylation, causing channel closure, glycerol accumulation, and enhanced survival under hyperosmotic stress. These events are all Hog1-independent. Our findings define the underlying molecular basis of a new mechanism for responding to hypertonic conditions. DOI:http://dx.doi.org/10.7554/eLife.09336.001
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Affiliation(s)
- Alexander Muir
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Françoise M Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Garrett Timmons
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Kristin L Leskoske
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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210
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An Updated Collection of Sequence Barcoded Temperature-Sensitive Alleles of Yeast Essential Genes. G3-GENES GENOMES GENETICS 2015; 5:1879-87. [PMID: 26175450 PMCID: PMC4555224 DOI: 10.1534/g3.115.019174] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Systematic analyses of essential gene function using mutant collections in Saccharomyces cerevisiae have been conducted using collections of heterozygous diploids, promoter shut-off alleles, through alleles with destabilized mRNA, destabilized protein, or bearing mutations that lead to a temperature-sensitive (ts) phenotype. We previously described a method for construction of barcoded ts alleles in a systematic fashion. Here we report the completion of this collection of alleles covering 600 essential yeast genes. This resource covers a larger gene repertoire than previous collections and provides a complementary set of strains suitable for single gene and genomic analyses. We use deep sequencing to characterize the amino acid changes leading to the ts phenotype in half of the alleles. We also use high-throughput approaches to describe the relative ts behavior of the alleles. Finally, we demonstrate the experimental usefulness of the collection in a high-content, functional genomic screen for ts alleles that increase spontaneous P-body formation. By increasing the number of alleles and improving the annotation, this ts collection will serve as a community resource for probing new aspects of biology for essential yeast genes.
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211
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Kachroo AH, Laurent JM, Yellman CM, Meyer AG, Wilke CO, Marcotte EM. Evolution. Systematic humanization of yeast genes reveals conserved functions and genetic modularity. Science 2015; 348:921-5. [PMID: 25999509 PMCID: PMC4718922 DOI: 10.1126/science.aaa0769] [Citation(s) in RCA: 281] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
To determine whether genes retain ancestral functions over a billion years of evolution and to identify principles of deep evolutionary divergence, we replaced 414 essential yeast genes with their human orthologs, assaying for complementation of lethal growth defects upon loss of the yeast genes. Nearly half (47%) of the yeast genes could be successfully humanized. Sequence similarity and expression only partly predicted replaceability. Instead, replaceability depended strongly on gene modules: Genes in the same process tended to be similarly replaceable (e.g., sterol biosynthesis) or not (e.g., DNA replication initiation). Simulations confirmed that selection for specific function can maintain replaceability despite extensive sequence divergence. Critical ancestral functions of many essential genes are thus retained in a pathway-specific manner, resilient to drift in sequences, splicing, and protein interfaces.
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Affiliation(s)
- Aashiq H Kachroo
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Jon M Laurent
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Christopher M Yellman
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Austin G Meyer
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Center for Computational Biology and Bioinformatics, University of Texas at Austin, Austin, TX 78712, USA
| | - Claus O Wilke
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Center for Computational Biology and Bioinformatics, University of Texas at Austin, Austin, TX 78712, USA. Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Edward M Marcotte
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Center for Computational Biology and Bioinformatics, University of Texas at Austin, Austin, TX 78712, USA. Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
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212
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Abstract
Quantitative high-throughput cell array phenotyping (Q-HTCP) is applied to the genomic collection of yeast gene deletion mutants for systematic, comprehensive assessment of the contribution of genes and gene combinations to any phenotype of interest (phenomic analysis). Interacting gene networks influence every phenotype. Genetic buffering refers to how gene interaction networks stabilize or destabilize a phenotype. Like genomics, phenomics varies in its resolution with there being a trade-off allocating a greater number of measurements per sample to enhance quantification of the phenotype vs. increasing the number of different samples by obtaining fewer measurements per sample. The Q-HTCP protocol we describe assesses 50,000-70,000 cultures per experiment by obtaining kinetic growth curves from time series imaging of agar cell arrays. This approach was developed for the yeast gene deletion strains, but it could be applied as well to other microbial mutant arrays grown on solid agar media. The methods we describe are for creation and maintenance of frozen stocks, liquid source array preparation, agar destination plate printing, image scanning, image analysis, curve fitting, and evaluation of gene interaction.
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213
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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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214
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Dilworth D, Nelson CJ. Rapid identification of chemical genetic interactions in Saccharomyces cerevisiae. J Vis Exp 2015:e52345. [PMID: 25867090 PMCID: PMC4401395 DOI: 10.3791/52345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Determining the mode of action of bioactive chemicals is of interest to a broad range of academic, pharmaceutical, and industrial scientists. Saccharomyces cerevisiae, or budding yeast, is a model eukaryote for which a complete collection of ~6,000 gene deletion mutants and hypomorphic essential gene mutants are commercially available. These collections of mutants can be used to systematically detect chemical-gene interactions, i.e. genes necessary to tolerate a chemical. This information, in turn, reports on the likely mode of action of the compound. Here we describe a protocol for the rapid identification of chemical-genetic interactions in budding yeast. We demonstrate the method using the chemotherapeutic agent 5-fluorouracil (5-FU), which has a well-defined mechanism of action. Our results show that the nuclear TRAMP RNA exosome and DNA repair enzymes are needed for proliferation in the presence of 5-FU, which is consistent with previous microarray based bar-coding chemical genetic approaches and the knowledge that 5-FU adversely affects both RNA and DNA metabolism. The required validation protocols of these high-throughput screens are also described.
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Affiliation(s)
- David Dilworth
- Department of Biochemistry and Microbiology, University of Victoria
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215
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O'Meara TR, Veri AO, Ketela T, Jiang B, Roemer T, Cowen LE. Global analysis of fungal morphology exposes mechanisms of host cell escape. Nat Commun 2015; 6:6741. [PMID: 25824284 PMCID: PMC4382923 DOI: 10.1038/ncomms7741] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 02/24/2015] [Indexed: 11/13/2022] Open
Abstract
Developmental transitions between single-cell yeast and multicellular filaments underpin virulence of diverse fungal pathogens. For the leading human fungal pathogen Candida albicans, filamentation is thought to be required for immune cell escape via induction of an inflammatory programmed cell death. Here we perform a genome-scale analysis of C. albicans morphogenesis and identify 102 negative morphogenetic regulators and 872 positive regulators, highlighting key roles for ergosterol biosynthesis and N-linked glycosylation. We demonstrate that C. albicans filamentation is not required for escape from host immune cells; instead, macrophage pyroptosis is driven by fungal cell-wall remodelling and exposure of glycosylated proteins in response to the macrophage phagosome. The capacity of killed, previously phagocytized cells to drive macrophage lysis is also observed with the distantly related fungal pathogen Cryptococcus neoformans. This study provides a global view of morphogenetic circuitry governing a key virulence trait, and illuminates a new mechanism by which fungi trigger host cell death. Several pathogenic fungi such as Candida albicans undergo transitions between single-celled forms and multicellular filaments. Here the authors perform a genome-scale analysis of C. albicans and show that, contrary to common belief, filamentation is not required for escape from host immune cells.
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Affiliation(s)
- Teresa R O'Meara
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Amanda O Veri
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Troy Ketela
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Bo Jiang
- Bioprocess Technology &Expression, Merck Research Laboratories, 2000 Galloping Hill Rd, Kenilworth, New Jersey 07033, USA
| | - Terry Roemer
- Department of Infectious Diseases, Merck Research Laboratories, 2000 Galloping Hill Rd, Kenilworth, New Jersey 07033, USA
| | - Leah E Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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216
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Mattiazzi Ušaj M, Brložnik M, Kaferle P, Žitnik M, Wolinski H, Leitner F, Kohlwein SD, Zupan B, Petrovič U. Genome-Wide Localization Study of Yeast Pex11 Identifies Peroxisome-Mitochondria Interactions through the ERMES Complex. J Mol Biol 2015; 427:2072-87. [PMID: 25769804 PMCID: PMC4429955 DOI: 10.1016/j.jmb.2015.03.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/01/2015] [Accepted: 03/04/2015] [Indexed: 11/29/2022]
Abstract
Pex11 is a peroxin that regulates the number of peroxisomes in eukaryotic cells. Recently, it was found that a mutation in one of the three mammalian paralogs, PEX11β, results in a neurological disorder. The molecular function of Pex11, however, is not known. Saccharomyces cerevisiae Pex11 has been shown to recruit to peroxisomes the mitochondrial fission machinery, thus enabling proliferation of peroxisomes. This process is essential for efficient fatty acid β-oxidation. In this study, we used high-content microscopy on a genome-wide scale to determine the subcellular localization pattern of yeast Pex11 in all non-essential gene deletion mutants, as well as in temperature-sensitive essential gene mutants. Pex11 localization and morphology of peroxisomes was profoundly affected by mutations in 104 different genes that were functionally classified. A group of genes encompassing MDM10, MDM12 and MDM34 that encode the mitochondrial and cytosolic components of the ERMES complex was analyzed in greater detail. Deletion of these genes caused a specifically altered Pex11 localization pattern, whereas deletion of MMM1, the gene encoding the fourth, endoplasmic-reticulum-associated component of the complex, did not result in an altered Pex11 localization or peroxisome morphology phenotype. Moreover, we found that Pex11 and Mdm34 physically interact and that Pex11 plays a role in establishing the contact sites between peroxisomes and mitochondria through the ERMES complex. Based on these results, we propose that the mitochondrial/cytosolic components of the ERMES complex establish a direct interaction between mitochondria and peroxisomes through Pex11. Molecular function of Pex11, a protein with roles in metabolism and disease, is unknown. Genome-wide screening determined subcellular localization of Pex11-GFP in yeast. Mutants defective in components of the ERMES complex show altered Pex11 localization. Pex11 physically interacts with the ERMES complex component Mdm34. ERMES complex and Pex11 mediate interaction between mitochondria and peroxisomes.
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Affiliation(s)
- M Mattiazzi Ušaj
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - M Brložnik
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - P Kaferle
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - M Žitnik
- Faculty of Computer and Information Science, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - H Wolinski
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - F Leitner
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - S D Kohlwein
- Institute of Molecular Biosciences, University of Graz, BioTechMed Graz, Humboldtstrasse 50, A-8010 Graz, Austria
| | - B Zupan
- Faculty of Computer and Information Science, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - U Petrovič
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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217
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Alings F, Sarin LP, Fufezan C, Drexler HCA, Leidel SA. An evolutionary approach uncovers a diverse response of tRNA 2-thiolation to elevated temperatures in yeast. RNA (NEW YORK, N.Y.) 2015; 21:202-12. [PMID: 25505025 PMCID: PMC4338348 DOI: 10.1261/rna.048199.114] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Chemical modifications of transfer RNA (tRNA) molecules are evolutionarily well conserved and critical for translation and tRNA structure. Little is known how these nucleoside modifications respond to physiological stress. Using mass spectrometry and complementary methods, we defined tRNA modification levels in six yeast species in response to elevated temperatures. We show that 2-thiolation of uridine at position 34 (s(2)U34) is impaired at temperatures exceeding 30°C in the commonly used Saccharomyces cerevisiae laboratory strains S288C and W303, and in Saccharomyces bayanus. Upon stress relief, thiolation levels recover and we find no evidence that modified tRNA or s(2)U34 nucleosides are actively removed. Our results suggest that loss of 2-thiolation follows accumulation of newly synthesized tRNA that lack s(2)U34 modification due to temperature sensitivity of the URM1 pathway in S. cerevisiae and S. bayanus. Furthermore, our analysis of the tRNA modification pattern in selected yeast species revealed two alternative phenotypes. Most strains moderately increase their tRNA modification levels in response to heat, possibly constituting a common adaptation to high temperatures. However, an overall reduction of nucleoside modifications was observed exclusively in S288C. This surprising finding emphasizes the importance of studies that utilize the power of evolutionary biology, and highlights the need for future systematic studies on tRNA modifications in additional model organisms.
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Affiliation(s)
- Fiona Alings
- RNA Biology Laboratory, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - L Peter Sarin
- RNA Biology Laboratory, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - Christian Fufezan
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Hannes C A Drexler
- Bioanalytical Mass Spectrometry Unit, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - Sebastian A Leidel
- RNA Biology Laboratory, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany Faculty of Medicine, University of Münster, 48149 Münster, Germany
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218
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Jin K, Musso G, Vlasblom J, Jessulat M, Deineko V, Negroni J, Mosca R, Malty R, Nguyen-Tran DH, Aoki H, Minic Z, Freywald T, Phanse S, Xiang Q, Freywald A, Aloy P, Zhang Z, Babu M. Yeast Mitochondrial Protein–Protein Interactions Reveal Diverse Complexes and Disease-Relevant Functional Relationships. J Proteome Res 2015; 14:1220-37. [DOI: 10.1021/pr501148q] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Ke Jin
- Terrence
Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Gabriel Musso
- Cardiovascular
Division, Brigham and Women’s Hospital, Boston, Massachusetts 02115, United States
- Department
of Medicine, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - James Vlasblom
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Matthew Jessulat
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Viktor Deineko
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Jacopo Negroni
- Joint
IRB−BSC Program in Computational Biology, IRB, Barcelona 08028, Spain
| | - Roberto Mosca
- Joint
IRB−BSC Program in Computational Biology, IRB, Barcelona 08028, Spain
| | - Ramy Malty
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Diem-Hang Nguyen-Tran
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Hiroyuki Aoki
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Zoran Minic
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Tanya Freywald
- Cancer Research
Unit, Saskatchewan Cancer Agency, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Sadhna Phanse
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Qian Xiang
- Terrence
Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - Andrew Freywald
- Cancer Research
Unit, Saskatchewan Cancer Agency, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Patrick Aloy
- Joint
IRB−BSC Program in Computational Biology, IRB, Barcelona 08028, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
| | - Zhaolei Zhang
- Terrence
Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - Mohan Babu
- Department
of Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
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219
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The proteasomal Rpn11 metalloprotease suppresses tombusvirus RNA recombination and promotes viral replication via facilitating assembly of the viral replicase complex. J Virol 2014; 89:2750-63. [PMID: 25540361 DOI: 10.1128/jvi.02620-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED RNA viruses co-opt a large number of cellular proteins that affect virus replication and, in some cases, viral genetic recombination. RNA recombination helps viruses in an evolutionary arms race with the host's antiviral responses and adaptation of viruses to new hosts. Tombusviruses and a yeast model host are used to identify cellular factors affecting RNA virus replication and RNA recombination. In this study, we have examined the role of the conserved Rpn11p metalloprotease subunit of the proteasome, which couples deubiquitination and degradation of proteasome substrates, in tombusvirus replication and recombination in Saccharomyces cerevisiae and plants. Depletion or mutations of Rpn11p lead to the rapid formation of viral RNA recombinants in combination with reduced levels of viral RNA replication in yeast or in vitro based on cell extracts. Rpn11p interacts with the viral replication proteins and is recruited to the viral replicase complex (VRC). Analysis of the multifunctional Rpn11p has revealed that the primary role of Rpn11p is to act as a "matchmaker" that brings the viral p92(pol) replication protein and the DDX3-like Ded1p/RH20 DEAD box helicases into VRCs. Overexpression of Ded1p can complement the defect observed in rpn11 mutant yeast by reducing TBSV recombination. This suggests that Rpn11p can suppress tombusvirus recombination via facilitating the recruitment of the cellular Ded1p helicase, which is a strong suppressor of viral recombination, into VRCs. Overall, this work demonstrates that the co-opted Rpn11p, which is involved in the assembly of the functional proteasome, also functions in the proper assembly of the tombusvirus VRCs. IMPORTANCE RNA viruses evolve rapidly due to genetic changes based on mutations and RNA recombination. Viral genetic recombination helps viruses in an evolutionary arms race with the host's antiviral responses and facilitates adaptation of viruses to new hosts. Cellular factors affect viral RNA recombination, although the role of the host in virus evolution is still understudied. In this study, we used a plant RNA virus, tombusvirus, to examine the role of a cellular proteasomal protein, called Rpn11, in tombusvirus recombination in a yeast model host, in plants, and in vitro. We found that the cellular Rpn11 is subverted for tombusvirus replication and Rpn11 has a proteasome-independent function in facilitating viral replication. When the Rpn11 level is knocked down or a mutated Rpn11 is expressed, then tombusvirus RNA goes through rapid viral recombination and evolution. Taken together, the results show that the co-opted cellular Rpn11 is a critical host factor for tombusviruses by regulating viral replication and genetic recombination.
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220
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Abstract
The budding yeast Saccharomyces cerevisiae is a powerful model organism for studying fundamental aspects of eukaryotic cell biology. This Primer article presents a brief historical perspective on the emergence of this organism as a premier experimental system over the course of the past century. An overview of the central features of the S. cerevisiae genome, including the nature of its genetic elements and general organization, is also provided. Some of the most common experimental tools and resources available to yeast geneticists are presented in a way designed to engage and challenge undergraduate and graduate students eager to learn more about the experimental amenability of budding yeast. Finally, a discussion of several major discoveries derived from yeast studies highlights the far-reaching impact that the yeast system has had and will continue to have on our understanding of a variety of cellular processes relevant to all eukaryotes, including humans.
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221
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Autophagy competes for a common phosphatidylethanolamine pool with major cellular PE-consuming pathways in Saccharomyces cerevisiae. Genetics 2014; 199:475-85. [PMID: 25519895 DOI: 10.1534/genetics.114.169797] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Autophagy is a highly regulated pathway that selectively degrades cellular constituents such as protein aggregates and excessive or damaged organelles. This transport route is characterized by engulfment of the targeted cargo by autophagosomes. The formation of these double-membrane vesicles requires the covalent conjugation of the ubiquitin-like protein Atg8 to phosphatidylethanolamine (PE). However, the origin of PE and the regulation of lipid flux required for autophagy remain poorly understood. Using a genetic screen, we found that the temperature-sensitive growth and intracellular membrane organization defects of mcd4-174 and mcd4-P301L mutants are suppressed by deletion of essential autophagy genes such as ATG1 or ATG7. MCD4 encodes an ethanolamine phosphate transferase that uses PE as a precursor for an essential step in the synthesis of the glycosylphosphatidylinositol (GPI) anchor used to link a subset of plasma membrane proteins to lipid bilayers. Similar to the deletion of CHO2, a gene encoding the enzyme converting PE to phosphatidylcholine (PC), deletion of ATG7 was able to restore lipidation and plasma membrane localization of the GPI-anchored protein Gas1 and normal organization of intracellular membranes. Conversely, overexpression of Cho2 was lethal in mcd4-174 cells grown at restrictive temperature. Quantitative lipid analysis revealed that PE levels are substantially reduced in the mcd4-174 mutant but can be restored by deletion of ATG7 or CHO2. Taken together, these data suggest that autophagy competes for a common PE pool with major cellular PE-consuming pathways such as the GPI anchor and PC synthesis, highlighting the possible interplay between these pathways and the existence of signals that may coordinate PE flux.
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222
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Cruz-Garcia D, Curwin AJ, Popoff JF, Bruns C, Duran JM, Malhotra V. Remodeling of secretory compartments creates CUPS during nutrient starvation. ACTA ACUST UNITED AC 2014; 207:695-703. [PMID: 25512390 PMCID: PMC4274258 DOI: 10.1083/jcb.201407119] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Upon starvation, Grh1, a peripheral membrane protein located at endoplasmic reticulum (ER) exit sites and early Golgi in Saccharomyces cerevisiae under growth conditions, relocates to a compartment called compartment for unconventional protein secretion (CUPS). Here we report that CUPS lack Golgi enzymes, but contain the coat protein complex II (COPII) vesicle tethering protein Uso1 and the Golgi t-SNARE Sed5. Interestingly, CUPS biogenesis is independent of COPII- and COPI-mediated membrane transport. Pik1- and Sec7-mediated membrane export from the late Golgi is required for complete assembly of CUPS, and Vps34 is needed for their maintenance. CUPS formation is triggered by glucose, but not nitrogen starvation. Moreover, upon return to growth conditions, CUPS are absorbed into the ER, and not the vacuole. Altogether our findings indicate that CUPS are not specialized autophagosomes as suggested previously. We suggest that starvation triggers relocation of secretory and endosomal membranes, but not their enzymes, to generate CUPS to sort and secrete proteins that do not enter, or are not processed by enzymes of the ER-Golgi pathway of secretion.
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Affiliation(s)
- David Cruz-Garcia
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Amy J Curwin
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Jean-François Popoff
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Caroline Bruns
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Juan M Duran
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Vivek Malhotra
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
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223
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Yang X, Shen Y, Garre E, Hao X, Krumlinde D, Cvijović M, Arens C, Nyström T, Liu B, Sunnerhagen P. Stress granule-defective mutants deregulate stress responsive transcripts. PLoS Genet 2014; 10:e1004763. [PMID: 25375155 PMCID: PMC4222700 DOI: 10.1371/journal.pgen.1004763] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 09/18/2014] [Indexed: 01/28/2023] Open
Abstract
To reduce expression of gene products not required under stress conditions, eukaryotic cells form large and complex cytoplasmic aggregates of RNA and proteins (stress granules; SGs), where transcripts are kept translationally inert. The overall composition of SGs, as well as their assembly requirements and regulation through stress-activated signaling pathways remain largely unknown. We have performed a genome-wide screen of S. cerevisiae gene deletion mutants for defects in SG formation upon glucose starvation stress. The screen revealed numerous genes not previously implicated in SG formation. Most mutants with strong phenotypes are equally SG defective when challenged with other stresses, but a considerable fraction is stress-specific. Proteins associated with SG defects are enriched in low-complexity regions, indicating that multiple weak macromolecule interactions are responsible for the structural integrity of SGs. Certain SG-defective mutants, but not all, display an enhanced heat-induced mutation rate. We found several mutations affecting the Ran GTPase, regulating nucleocytoplasmic transport of RNA and proteins, to confer SG defects. Unexpectedly, we found stress-regulated transcripts to reach more extreme levels in mutants unable to form SGs: stress-induced mRNAs accumulate to higher levels than in the wild-type, whereas stress-repressed mRNAs are reduced further in such mutants. Our findings are consistent with the view that, not only are SGs being regulated by stress signaling pathways, but SGs also modulate the extent of stress responses. We speculate that nucleocytoplasmic shuttling of RNA-binding proteins is required for gene expression regulation during stress, and that SGs modulate this traffic. The absence of SGs thus leads the cell to excessive, and potentially deleterious, reactions to stress. When cells encounter harsh conditions, they face an energy crisis since the stress will reduce their energy production, and at the same time cause extra demands on energy expenditure. To tackle this dilemma, cells under stress form giant agglomerates of RNA and protein, called stress granules. In these, mRNA molecules are kept silent, preventing waste of energy on producing proteins not needed under these conditions. A few mRNAs, encoding proteins required for the cell to survive, stay outside of stress granules and escape this silencing. This mechanism can protect plants and microbes against cold spells or heat shocks, and human cells exposed to oxidative damage or toxic drugs. We have investigated which genes are necessary to form stress granules, and their impact on the stress response. We discovered that mutant cells unable to form stress granules overreacted to stress, in that they produced much higher levels of the induced mRNAs. We think this means that gene regulatory proteins are sequestered inside stress granules, inhibiting their action. Stress granules may thus function as moderators that dampen the stress response, safeguarding the cell against excessive reactions.
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Affiliation(s)
- Xiaoxue Yang
- School of Life Science and Engineering, Harbin Institute of Technology, Harbin, China
| | - Yi Shen
- School of Life Science and Engineering, Harbin Institute of Technology, Harbin, China
| | - Elena Garre
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
| | - Xinxin Hao
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
| | - Daniel Krumlinde
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
| | - Marija Cvijović
- Department of Mathematical Sciences, Chalmers University of Technology, Göteborg, Sweden
- Department of Mathematical Sciences, University of Gothenburg, Göteborg, Sweden
| | - Christina Arens
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
| | - Thomas Nyström
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
| | - Beidong Liu
- School of Life Science and Engineering, Harbin Institute of Technology, Harbin, China
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
- * E-mail: (BL); (PS)
| | - Per Sunnerhagen
- Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Göteborg, Sweden
- * E-mail: (BL); (PS)
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224
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Fang NN, Chan GT, Zhu M, Comyn SA, Persaud A, Deshaies RJ, Rotin D, Gsponer J, Mayor T. Rsp5/Nedd4 is the main ubiquitin ligase that targets cytosolic misfolded proteins following heat stress. Nat Cell Biol 2014; 16:1227-37. [PMID: 25344756 PMCID: PMC5224936 DOI: 10.1038/ncb3054] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 09/17/2014] [Indexed: 12/14/2022]
Abstract
The heat-shock response is a complex cellular program that induces major changes in protein translation, folding and degradation to alleviate toxicity caused by protein misfolding. Although heat shock has been widely used to study proteostasis, it remained unclear how misfolded proteins are targeted for proteolysis in these conditions. We found that Rsp5 and its mammalian homologue Nedd4 are important E3 ligases responsible for the increased ubiquitylation induced by heat stress. We determined that Rsp5 ubiquitylates mainly cytosolic misfolded proteins upon heat shock for proteasome degradation. We found that ubiquitylation of heat-induced substrates requires the Hsp40 co-chaperone Ydj1 that is further associated with Rsp5 upon heat shock. In addition, ubiquitylation is also promoted by PY Rsp5-binding motifs found primarily in the structured regions of stress-induced substrates, which can act as heat-induced degrons. Our results support a bipartite recognition mechanism combining direct and chaperone-dependent ubiquitylation of misfolded cytosolic proteins by Rsp5.
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Affiliation(s)
- Nancy N Fang
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
| | - Gerard T Chan
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
| | - Mang Zhu
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
| | - Sophie A Comyn
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
| | - Avinash Persaud
- Program in Cell Biology, Hospital for Sick Children, and Biochemistry Department, University of Toronto, Toronto, Ontario M5G 0A4, Canada
| | - Raymond J Deshaies
- Howard Hughes Medical Institute, Division of Biology and Biological Engineering, 114-96 Caltech, 1200 E. California Boulevard Pasadena, California 91125, USA
| | - Daniela Rotin
- Program in Cell Biology, Hospital for Sick Children, and Biochemistry Department, University of Toronto, Toronto, Ontario M5G 0A4, Canada
| | - Joerg Gsponer
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
| | - Thibault Mayor
- Department of Biochemistry and Molecular Biology, Centre for High-Throughput Biology, University of British Columbia, 2125 East Mall Vancouver, British Columbia V6T1Z4, Canada
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225
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Paul JM, Templeton SD, Baharani A, Freywald A, Vizeacoumar FJ. Building high-resolution synthetic lethal networks: a 'Google map' of the cancer cell. Trends Mol Med 2014; 20:704-15. [PMID: 25446836 DOI: 10.1016/j.molmed.2014.09.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/05/2014] [Accepted: 09/17/2014] [Indexed: 02/08/2023]
Abstract
The most commonly used therapies for cancer involve delivering high doses of radiation or toxic chemicals to the patient that also cause substantial damage to normal tissue. To overcome this, researchers have recently resorted to a basic biological concept called 'synthetic lethality' (SL) that takes advantage of interactions between gene pairs. The identification of SL interactions is of considerable therapeutic interest because if a particular gene is SL with a tumor-causing mutation, then the targeting that gene carries therapeutic advantages. Mapping these interactions in the context of human cancer cells could hold the key to effective, targeted cancer treatments. In this review, we cover the recent advances that aim to identify these SL interactions using unbiased genetic screens.
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Affiliation(s)
- James M Paul
- Department of Biochemistry, University of Saskatchewan, Saskatoon, S7N 5E5 Canada; Department of Pathology, University of Saskatchewan, Saskatoon, S7N 0W8 Canada
| | - Shaina D Templeton
- Department of Biochemistry, University of Saskatchewan, Saskatoon, S7N 5E5 Canada
| | - Akanksha Baharani
- Department of Biochemistry, University of Saskatchewan, Saskatoon, S7N 5E5 Canada
| | - Andrew Freywald
- Department of Pathology, University of Saskatchewan, Saskatoon, S7N 0W8 Canada
| | - Franco J Vizeacoumar
- Department of Biochemistry, University of Saskatchewan, Saskatoon, S7N 5E5 Canada; Saskatchewan Cancer Agency, Saskatoon, SK S7N 4H4, Canada.
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226
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Zhou C, Slaughter BD, Unruh JR, Guo F, Yu Z, Mickey K, Narkar A, Ross RT, McClain M, Li R. Organelle-based aggregation and retention of damaged proteins in asymmetrically dividing cells. Cell 2014; 159:530-42. [PMID: 25417105 DOI: 10.1016/j.cell.2014.09.026] [Citation(s) in RCA: 172] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 08/07/2014] [Accepted: 09/10/2014] [Indexed: 12/26/2022]
Abstract
Aggregation of damaged or misfolded proteins is a protective mechanism against proteotoxic stress, abnormalities of which underlie many aging-related diseases. Here, we show that in asymmetrically dividing yeast cells, aggregation of cytosolic misfolded proteins does not occur spontaneously but requires new polypeptide synthesis and is restricted to the surface of ER, which harbors the majority of active translation sites. Protein aggregates formed on ER are frequently also associated with or are later captured by mitochondria, greatly constraining aggregate mobility. During mitosis, aggregates are tethered to well-anchored maternal mitochondria, whereas mitochondria acquired by the bud are largely free of aggregates. Disruption of aggregate-mitochondria association resulted in increased mobility and leakage of mother-accumulated aggregates into the bud. Cells with advanced replicative age exhibit gradual decline of aggregates-mitochondria association, likely contributing to their diminished ability to rejuvenate through asymmetric cell division.
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Affiliation(s)
- Chuankai Zhou
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Brian D Slaughter
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Jay R Unruh
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Fengli Guo
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Zulin Yu
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Kristen Mickey
- Department of Pharmacolgy, Toxicology, and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Akshay Narkar
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Rhonda Trimble Ross
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Melainia McClain
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA
| | - Rong Li
- Stowers Institute for Medical Research, 1000 East 50(th) Street, Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
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227
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Wu J, Hopper AK. Healing for destruction: tRNA intron degradation in yeast is a two-step cytoplasmic process catalyzed by tRNA ligase Rlg1 and 5'-to-3' exonuclease Xrn1. Genes Dev 2014; 28:1556-61. [PMID: 25030695 PMCID: PMC4102763 DOI: 10.1101/gad.244673.114] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In eukaryotes and archaea, tRNA splicing generates free intron molecules. Although ∼ 600,000 introns are produced per generation in yeast, they are barely detectable in cells, indicating efficient turnover of introns. Through a genome-wide search for genes involved in tRNA biology in yeast, we uncovered the mechanism for intron turnover. This process requires healing of the 5' termini of linear introns by the tRNA ligase Rlg1 and destruction by the cytoplasmic tRNA quality control 5'-to-3' exonuclease Xrn1, which has specificity for RNAs with 5' monophosphate.
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Affiliation(s)
- Jingyan Wu
- Department of Molecular Genetics, Graduate Program in Plant Cellular and Molecular Biology, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
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228
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Sasvari Z, Alatriste Gonzalez P, Nagy PD. Tombusvirus-yeast interactions identify conserved cell-intrinsic viral restriction factors. FRONTIERS IN PLANT SCIENCE 2014; 5:383. [PMID: 25157258 PMCID: PMC4127529 DOI: 10.3389/fpls.2014.00383] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Accepted: 07/18/2014] [Indexed: 05/23/2023]
Abstract
To combat viral infections, plants possess innate and adaptive immune pathways, such as RNA silencing, R gene and recessive gene-mediated resistance mechanisms. However, it is likely that additional cell-intrinsic restriction factors (CIRF) are also involved in limiting plant virus replication. This review discusses novel CIRFs with antiviral functions, many of them RNA-binding proteins or affecting the RNA binding activities of viral replication proteins. The CIRFs against tombusviruses have been identified in yeast (Saccharomyces cerevisiae), which is developed as an advanced model organism. Grouping of the identified CIRFs based on their known cellular functions and subcellular localization in yeast reveals that TBSV replication is limited by a wide variety of host gene functions. Yeast proteins with the highest connectivity in the network map include the well-characterized Xrn1p 5'-3' exoribonuclease, Act1p actin protein and Cse4p centromere protein. The protein network map also reveals an important interplay between the pro-viral Hsp70 cellular chaperone and the antiviral co-chaperones, and possibly key roles for the ribosomal or ribosome-associated factors. We discuss the antiviral functions of selected CIRFs, such as the RNA binding nucleolin, ribonucleases, WW-domain proteins, single- and multi-domain cyclophilins, TPR-domain co-chaperones and cellular ion pumps. These restriction factors frequently target the RNA-binding region in the viral replication proteins, thus interfering with the recruitment of the viral RNA for replication and the assembly of the membrane-bound viral replicase. Although many of the characterized CIRFs act directly against TBSV, we propose that the TPR-domain co-chaperones function as "guardians" of the cellular Hsp70 chaperone system, which is subverted efficiently by TBSV for viral replicase assembly in the absence of the TPR-domain co-chaperones.
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Affiliation(s)
| | | | - Peter D. Nagy
- *Correspondence: Peter D. Nagy, Department of Plant Pathology, University of Kentucky, 201F Plant Science Building, Lexington, KY 40546, USA e-mail:
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229
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Li T, Belda-Palazón B, Ferrando A, Alepuz P. Fertility and polarized cell growth depends on eIF5A for translation of polyproline-rich formins in Saccharomyces cerevisiae. Genetics 2014; 197:1191-200. [PMID: 24923804 PMCID: PMC4125393 DOI: 10.1534/genetics.114.166926] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 06/05/2014] [Indexed: 01/15/2023] Open
Abstract
eIF5A is an essential and evolutionary conserved translation elongation factor, which has recently been proposed to be required for the translation of proteins with consecutive prolines. The binding of eIF5A to ribosomes occurs upon its activation by hypusination, a modification that requires spermidine, an essential factor for mammalian fertility that also promotes yeast mating. We show that in response to pheromone, hypusinated eIF5A is required for shmoo formation, localization of polarisome components, induction of cell fusion proteins, and actin assembly in yeast. We also show that eIF5A is required for the translation of Bni1, a proline-rich formin involved in polarized growth during shmoo formation. Our data indicate that translation of the polyproline motifs in Bni1 is eIF5A dependent and this translation dependency is lost upon deletion of the polyprolines. Moreover, an exogenous increase in Bni1 protein levels partially restores the defect in shmoo formation seen in eIF5A mutants. Overall, our results identify eIF5A as a novel and essential regulator of yeast mating through formin translation. Since eIF5A and polyproline formins are conserved across species, our results also suggest that eIF5A-dependent translation of formins could regulate polarized growth in such processes as fertility and cancer in higher eukaryotes.
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Affiliation(s)
- Tianlu Li
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universitat de València, E-46100 Burjassot, Valencia, Spain
| | - Borja Belda-Palazón
- Instituto de Biología Molecular y Celular de Plantas, Centro Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022 Valencia, Spain
| | - Alejandro Ferrando
- Instituto de Biología Molecular y Celular de Plantas, Centro Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022 Valencia, Spain
| | - Paula Alepuz
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universitat de València, E-46100 Burjassot, Valencia, Spain
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230
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Song J, Yang Q, Yang J, Larsson L, Hao X, Zhu X, Malmgren-Hill S, Cvijovic M, Fernandez-Rodriguez J, Grantham J, Gustafsson CM, Liu B, Nyström T. Essential genetic interactors of SIR2 required for spatial sequestration and asymmetrical inheritance of protein aggregates. PLoS Genet 2014; 10:e1004539. [PMID: 25079602 PMCID: PMC4117435 DOI: 10.1371/journal.pgen.1004539] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 06/16/2014] [Indexed: 11/19/2022] Open
Abstract
Sir2 is a central regulator of yeast aging and its deficiency increases daughter cell inheritance of stress- and aging-induced misfolded proteins deposited in aggregates and inclusion bodies. Here, by quantifying traits predicted to affect aggregate inheritance in a passive manner, we found that a passive diffusion model cannot explain Sir2-dependent failures in mother-biased segregation of either the small aggregates formed by the misfolded Huntingtin, Htt103Q, disease protein or heat-induced Hsp104-associated aggregates. Instead, we found that the genetic interaction network of SIR2 comprises specific essential genes required for mother-biased segregation including those encoding components of the actin cytoskeleton, the actin-associated myosin V motor protein Myo2, and the actin organization protein calmodulin, Cmd1. Co-staining with Hsp104-GFP demonstrated that misfolded Htt103Q is sequestered into small aggregates, akin to stress foci formed upon heat stress, that fail to coalesce into inclusion bodies. Importantly, these Htt103Q foci, as well as the ATPase-defective Hsp104Y662A-associated structures previously shown to be stable stress foci, co-localized with Cmd1 and Myo2-enriched structures and super-resolution 3-D microscopy demonstrated that they are associated with actin cables. Moreover, we found that Hsp42 is required for formation of heat-induced Hsp104Y662A foci but not Htt103Q foci suggesting that the routes employed for foci formation are not identical. In addition to genes involved in actin-dependent processes, SIR2-interactors required for asymmetrical inheritance of Htt103Q and heat-induced aggregates encode essential sec genes involved in ER-to-Golgi trafficking/ER homeostasis.
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Affiliation(s)
- Jia Song
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Qian Yang
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Junsheng Yang
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Lisa Larsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Xinxin Hao
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Xuefeng Zhu
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Sandra Malmgren-Hill
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Marija Cvijovic
- Mathematical Sciences, University of Gothenburg, Gothenburg, Sweden
- Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | | | - Julie Grantham
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
| | - Claes M. Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Beidong Liu
- School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
- * E-mail:
| | - Thomas Nyström
- Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
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231
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Huang HY, Hopper AK. Separate responses of karyopherins to glucose and amino acid availability regulate nucleocytoplasmic transport. Mol Biol Cell 2014; 25:2840-52. [PMID: 25057022 PMCID: PMC4161518 DOI: 10.1091/mbc.e14-04-0948] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The subcellular distribution of yeast β-importins inverts upon acute glucose deprivation, likely due to collapse of the RanGTP nuclear–cytoplasmic gradient. This redistribution of β-importins likely results in rapid widespread alterations of the traffic of macromolecules between the nucleus and cytoplasm in response to glucose limitation. The importin-β family members (karyopherins) mediate the majority of nucleocytoplasmic transport. Msn5 and Los1, members of the importin-β family, function in tRNA nuclear export. tRNAs move bidirectionally between the nucleus and the cytoplasm. Nuclear tRNA accumulation occurs upon amino acid (aa) or glucose deprivation. To understand the mechanisms regulating tRNA subcellular trafficking, we investigated whether Msn5 and Los1 are regulated in response to nutrient availability. We provide evidence that tRNA subcellular trafficking is regulated by distinct aa-sensitive and glucose-sensitive mechanisms. Subcellular distributions of Msn5 and Los1 are altered upon glucose deprivation but not aa deprivation. Redistribution of tRNA exportins from the nucleus to the cytoplasm likely provides one mechanism for tRNA nuclear distribution upon glucose deprivation. We extended our studies to other members of the importin-β family and found that all tested karyopherins invert their subcellular distributions upon glucose deprivation but not aa deprivation. Glucose availability regulates the subcellular distributions of karyopherins likely due to alteration of the RanGTP gradient since glucose deprivation causes redistribution of Ran. Thus nuclear–cytoplasmic distribution of macromolecules is likely generally altered upon glucose deprivation due to collapse of the RanGTP gradient and redistribution of karyopherins between the nucleus and the cytoplasm.
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Affiliation(s)
- Hsiao-Yun Huang
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, OH 43210 Graduate Program in Molecular, Cellular, and Developmental Biology, Ohio State University, Columbus, OH 43210
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, OH 43210
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232
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Peplowska K, Wallek AU, Storchova Z. Sgo1 regulates both condensin and Ipl1/Aurora B to promote chromosome biorientation. PLoS Genet 2014; 10:e1004411. [PMID: 24945276 PMCID: PMC4063673 DOI: 10.1371/journal.pgen.1004411] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 04/16/2014] [Indexed: 12/23/2022] Open
Abstract
Correct chromosome segregation is essential in order to prevent aneuploidy. To segregate sister chromatids equally to daughter cells, the sisters must attach to microtubules emanating from opposite spindle poles. This so-called biorientation manifests itself by increased tension and conformational changes across kinetochores and pericentric chromatin. Tensionless attachments are dissolved by the activity of the conserved mitotic kinase Aurora B/Ipl1, thereby promoting the formation of correctly attached chromosomes. Recruitment of the conserved centromeric protein shugoshin is essential for biorientation, but its exact role has been enigmatic. Here, we identify a novel function of shugoshin (Sgo1 in budding yeast) that together with the protein phosphatase PP2A-Rts1 ensures localization of condensin to the centromeric chromatin in yeast Saccharomyces cerevisiae. Failure to recruit condensin results in an abnormal conformation of the pericentric region and impairs the correction of tensionless chromosome attachments. Moreover, we found that shugoshin is required for maintaining Aurora B/Ipl1 localization on kinetochores during metaphase. Thus, shugoshin has a dual function in promoting biorientation in budding yeast: first, by its ability to facilitate condensin recruitment it modulates the conformation of the pericentric chromatin. Second, shugoshin contributes to the maintenance of Aurora B/Ipl1 at the kinetochore during gradual establishment of bipolarity in budding yeast mitosis. Our findings identify shugoshin as a versatile molecular adaptor that governs chromosome biorientation. Accurate chromosome segregation is required for the equal distribution of genetic information to progeny. Failure to equally segregate chromosomes leads to aneuploidy, cell death or cancer. Proteins of the conserved shugoshin family contribute to accurate chromosome segregation in both meiosis and mitosis. The role of shugoshin in protection of centromeric cohesion during meiosis is well understood, but only little is known about shugoshin's function during mitosis. We show that Sgo1 mediates localization of the heterotrimeric phosphatase PP2A-Rts1 to the centromere and that this is in turn important for the efficient recruitment of condensin to the centromere. The failure to load centromeric condensin results in a defect during correction of improper microtubule-kinetochore attachments. Moreover, Sgo1 facilitates the maintenance of a centromeric pool of Aurora B/Ipl1, a conserved mitotic kinase essential for the correction of faulty microtubule-kinetochore attachments. Our results show that Sgo1 operates as a multifunctional hub that coordinates two centromeric functions essential for correct chromosome segregation.
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Affiliation(s)
- Karolina Peplowska
- Group Maintenance of Genome Stability, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Andreas U. Wallek
- Group Maintenance of Genome Stability, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Zuzana Storchova
- Group Maintenance of Genome Stability, Max Planck Institute of Biochemistry, Martinsried, Germany
- * E-mail:
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233
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Abstract
The yeast deletion collections comprise >21,000 mutant strains that carry precise start-to-stop deletions of ∼6000 open reading frames. This collection includes heterozygous and homozygous diploids, and haploids of both MATa and MATα mating types. The yeast deletion collection, or yeast knockout (YKO) set, represents the first and only complete, systematically constructed deletion collection available for any organism. Conceived during the Saccharomyces cerevisiae sequencing project, work on the project began in 1998 and was completed in 2002. The YKO strains have been used in numerous laboratories in >1000 genome-wide screens. This landmark genome project has inspired development of numerous genome-wide technologies in organisms from yeast to man. Notable spinoff technologies include synthetic genetic array and HIPHOP chemogenomics. In this retrospective, we briefly describe the yeast deletion project and some of its most noteworthy biological contributions and the impact that these collections have had on the yeast research community and on genomics in general.
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234
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Parts L. Genome-wide mapping of cellular traits using yeast. Yeast 2014; 31:197-205. [PMID: 24700360 DOI: 10.1002/yea.3010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 03/24/2014] [Accepted: 03/25/2014] [Indexed: 11/09/2022] Open
Abstract
Yeast has long enjoyed superiority as a genetic model because of its short generation time and ease of generating alleles for genetic analysis. However, recent developments of guided nucleases for genome editing in higher eukaryotes, and funding pressures for translational findings, force all model organism communities to reaffirm and rearticulate the advantages of their chosen creature. Here I examine the utility of budding yeast for understanding the genetic basis of cellular traits, using natural variation as well as classical genetic perturbations, and its future prospects compared to undertaking the work in human cell lines. Will yeast remain central, or will it join the likes of phage as an early model that is no longer widely used to answer the pressing questions?
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Affiliation(s)
- Leopold Parts
- Department of Molecular Genetics, Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Canada
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235
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Kovalev N, Nagy PD. The expanding functions of cellular helicases: the tombusvirus RNA replication enhancer co-opts the plant eIF4AIII-like AtRH2 and the DDX5-like AtRH5 DEAD-box RNA helicases to promote viral asymmetric RNA replication. PLoS Pathog 2014; 10:e1004051. [PMID: 24743583 PMCID: PMC3990711 DOI: 10.1371/journal.ppat.1004051] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 02/19/2014] [Indexed: 12/17/2022] Open
Abstract
Replication of plus-strand RNA viruses depends on recruited host factors that aid several critical steps during replication. Several of the co-opted host factors bind to the viral RNA, which plays multiple roles, including mRNA function, as an assembly platform for the viral replicase (VRC), template for RNA synthesis, and encapsidation during infection. It is likely that remodeling of the viral RNAs and RNA-protein complexes during the switch from one step to another requires RNA helicases. In this paper, we have discovered a second group of cellular RNA helicases, including the eIF4AIII-like yeast Fal1p and the DDX5-like Dbp3p and the orthologous plant AtRH2 and AtRH5 DEAD box helicases, which are co-opted by tombusviruses. Unlike the previously characterized DDX3-like AtRH20/Ded1p helicases that bind to the 3' terminal promoter region in the viral minus-strand (-)RNA, the other class of eIF4AIII-like RNA helicases bind to a different cis-acting element, namely the 5' proximal RIII(-) replication enhancer (REN) element in the TBSV (-)RNA. We show that the binding of AtRH2 and AtRH5 helicases to the TBSV (-)RNA could unwind the dsRNA structure within the RIII(-) REN. This unique characteristic allows the eIF4AIII-like helicases to perform novel pro-viral functions involving the RIII(-) REN in stimulation of plus-strand (+)RNA synthesis. We also show that AtRH2 and AtRH5 helicases are components of the tombusvirus VRCs based on co-purification experiments. We propose that eIF4AIII-like helicases destabilize dsRNA replication intermediate within the RIII(-) REN that promotes bringing the 5' and 3' terminal (-)RNA sequences in close vicinity via long-range RNA-RNA base pairing. This newly formed RNA structure promoted by eIF4AIII helicase together with AtRH20 helicase might facilitate the recycling of the viral replicases for multiple rounds of (+)-strand synthesis, thus resulting in asymmetrical viral replication.
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Affiliation(s)
- Nikolay Kovalev
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Peter D. Nagy
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
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236
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Nagy PD, Pogany J, Lin JY. How yeast can be used as a genetic platform to explore virus-host interactions: from 'omics' to functional studies. Trends Microbiol 2014; 22:309-16. [PMID: 24647076 DOI: 10.1016/j.tim.2014.02.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/05/2014] [Accepted: 02/10/2014] [Indexed: 01/07/2023]
Abstract
The yeast Saccharomyces cerevisiae is an advanced model organism that has emerged as an effective host to gain insights into the intricate interactions of viruses with host cells. RNA viruses have limited coding potential and need to coopt numerous host cellular factors to facilitate their replication. To identify the host factors subverted by viruses, high-throughput genomics and global proteomics approaches have been performed with plant viruses such as brome mosaic virus (BMV) and tomato bushy stunt virus (TBSV). Accordingly, several hundred susceptibility and restriction factors for BMV and TBSV have been identified using yeast as a model host. Amazingly, host factors affecting viral genetic recombination and evolution have also been identified in genome-wide screens in yeast. The roles of many yeast host factors involved in various steps of the viral replication process have been validated by exploiting the orthologous genes in plant hosts. This Opinion summarizes the advantages of using simple viruses and yeast model host to advance our general understanding of virus-host interactions. The knowledge gained on host factors could lead to novel specific or broad-range resistance and antiviral tools against viruses.
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Affiliation(s)
- Peter D Nagy
- Department of Plant Pathology, University of Kentucky, Lexington, KY, USA.
| | - Judit Pogany
- Department of Plant Pathology, University of Kentucky, Lexington, KY, USA
| | - Jing-Yi Lin
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
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237
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Rossi D, Galvão FC, Bellato HM, Boldrin PEG, Andrews BJ, Valentini SR, Zanelli CF. eIF5A has a function in the cotranslational translocation of proteins into the ER. Amino Acids 2014; 46:645-53. [PMID: 24306454 DOI: 10.1007/s00726-013-1618-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 11/01/2013] [Indexed: 10/25/2022]
Abstract
The putative eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved and essential protein present in all organisms except bacteria. To be activated, eIF5A requires the conversion of a specific residue of lysine into hypusine. This hypusine modification occurs posttranslationally in two enzymatic steps, and the polyamine spermidine is the substrate. Despite having an essential function in translation elongation, the critical role played by eIF5A remains unclear. In addition to demonstrating genetic interactions with translation factors, eIF5A mutants genetically interact with mutations in YPT1, which encodes an essential protein involved in endoplasmic reticulum (ER)-to-Golgi vesicle transport. In this study, we investigated the correlation between the function of eIF5A in translation and secretion in yeast. The results of in vivo translocation assays and genetic interaction analyses suggest a specific role for eIF5A in the cotranslational translocation of proteins into the ER, but not in the posttranslational pathway. Additionally, we observed that a block in eIF5A activation up-regulates stress-induced chaperones, which also occurs when SRP function is lost. Finally, loss of eIF5A function affects binding of the ribosome-nascent chain complex to SRP. These results link eIF5A function in translation with a role of SRP in the cell and may help explain the dual effects of eIF5A in differential and general translation.
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Affiliation(s)
- Danuza Rossi
- Department of Biological Sciences, School of Pharmaceutical Sciences, Univ Estadual Paulista, UNESP, Araraquara, SP, Brazil
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238
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Kwon MJ, Arentshorst M, Fiedler M, de Groen FLM, Punt PJ, Meyer V, Ram AFJ. Molecular genetic analysis of vesicular transport in Aspergillus niger reveals partial conservation of the molecular mechanism of exocytosis in fungi. Microbiology (Reading) 2014; 160:316-329. [DOI: 10.1099/mic.0.074252-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The filamentous fungus Aspergillus niger is an industrially exploited protein expression platform, well known for its capacity to secrete high levels of proteins. To study the process of protein secretion in A. niger, we established a GFP-v-SNARE reporter strain in which the trafficking and dynamics of secretory vesicles can be followed in vivo. The biological role of putative A. niger orthologues of seven secretion-specific genes, known to function in key aspects of the protein secretion machinery in Saccharomyces cerevisiae, was analysed by constructing respective gene deletion mutants in the GFP-v-SNARE reporter strain. Comparison of the deletion phenotype of conserved proteins functioning in the secretory pathway revealed common features but also interesting differences between S. cerevisiae and A. niger. Deletion of the S. cerevisiae Sec2p orthologue in A. niger (SecB), encoding a guanine exchange factor for the GTPase Sec4p (SrgA in A. niger), did not have an obvious phenotype, while SEC2 deletion in S. cerevisiae is lethal. Similarly, deletion of the A. niger orthologue of the S. cerevisiae exocyst subunit Sec3p (SecC) did not result in a lethal phenotype as in S. cerevisiae, although severe growth reduction of A. niger was observed. Deletion of secA, secH and ssoA (encoding SecA, SecH and SsoA the A. niger orthologues of S. cerevisiae Sec1p, Sec8p and Sso1/2p, respectively) showed that these genes are essential for A. niger, similar to the situation in S. cerevisiae. These data demonstrate that the orchestration of exocyst-mediated vesicle transport is only partially conserved in S. cerevisiae and A. niger.
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Affiliation(s)
- Min Jin Kwon
- Kluyver Centre for Genomics of Industrial Fermentation, P.O. Box 5057, 2600 GA Delft, The Netherlands
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Mark Arentshorst
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Markus Fiedler
- Department Applied and Molecular Microbiology, Institute of Biotechnology, Berlin University of Technology, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
| | - Florence L. M. de Groen
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Peter J. Punt
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Vera Meyer
- Department Applied and Molecular Microbiology, Institute of Biotechnology, Berlin University of Technology, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
- Kluyver Centre for Genomics of Industrial Fermentation, P.O. Box 5057, 2600 GA Delft, The Netherlands
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Arthur F. J. Ram
- Kluyver Centre for Genomics of Industrial Fermentation, P.O. Box 5057, 2600 GA Delft, The Netherlands
- Department Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
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239
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Kurat CF, Recht J, Radovani E, Durbic T, Andrews B, Fillingham J. Regulation of histone gene transcription in yeast. Cell Mol Life Sci 2014; 71:599-613. [PMID: 23974242 PMCID: PMC11113579 DOI: 10.1007/s00018-013-1443-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/10/2013] [Accepted: 07/29/2013] [Indexed: 12/11/2022]
Abstract
Histones are the primary protein component of chromatin, the mixture of DNA and proteins that packages the genetic material in eukaryotes. Large amounts of histones are required during the S phase of the cell cycle when genome replication occurs. However, ectopic expression of histones during other cell cycle phases is toxic; thus, histone expression is restricted to the S phase and is tightly regulated at multiple levels, including transcriptional, post-transcriptional, translational, and post-translational. In this review, we discuss mechanisms of regulation of histone gene expression with emphasis on the transcriptional regulation of the replication-dependent histone genes in the model yeast Saccharomyces cerevisiae.
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Affiliation(s)
- Christoph F. Kurat
- The Donnelly Center, University of Toronto, Toronto, ON M5S 3E1 Canada
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S 3E1 Canada
| | | | - Ernest Radovani
- Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B 2K3 Canada
| | - Tanja Durbic
- Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B 2K3 Canada
| | - Brenda Andrews
- The Donnelly Center, University of Toronto, Toronto, ON M5S 3E1 Canada
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S 3E1 Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 3E1 Canada
| | - Jeffrey Fillingham
- Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B 2K3 Canada
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Chemical suppression of defects in mitotic spindle assembly, redox control, and sterol biosynthesis by hydroxyurea. G3-GENES GENOMES GENETICS 2014; 4:39-48. [PMID: 24192836 PMCID: PMC3887538 DOI: 10.1534/g3.113.009100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We describe the results of a systematic search for a class of hitherto-overlooked chemical-genetic interactions in the Saccharomyces cerevisiae genome, which exists between a detrimental genetic mutation and a chemical/drug that can ameliorate, rather than exacerbate, that detriment. We refer to this type of interaction as “chemical suppression.” Our work was driven by the hypothesis that genome instability in a certain class of mutants could be alleviated by mild replication inhibition using chemicals/drugs. We queried a collection of conditionally lethal, i.e., temperature-sensitive, alleles representing 40% of the yeast essential genes for those mutants whose growth defect can be suppressed by hydroxyurea (HU), known as a potent DNA replication inhibitor, at the restrictive temperature. Unexpectedly, we identified a number of mutants defective in diverse cellular pathways other than DNA replication. Here we report that HU suppresses selected mutants defective in the kinetochore-microtubule attachment pathway during mitotic chromosome segregation. HU also suppresses an ero1-1 mutant defective for a thiol oxidase of the endoplasmic reticulum by providing oxidation equivalents. Finally, we report that HU suppresses an erg26-1 mutant defective for a C-3 sterol dehydrogenase through regulating iron homeostasis and in turn impacting ergosterol biosynthesis. We further demonstrate that cells carrying the erg26-1 mutation show an increased rate of mitochondrial DNA loss and delayed G1 to S phase transition. We conclude that systematic gathering of a compendium of “chemical suppression” of yeast mutants by genotoxic drugs will not only enable the identification of novel functions of both chemicals and genes, but also have profound implications in cautionary measures of anticancer intervention in humans.
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Sasabe M, Shintani S, Kintaka R, Kaizu K, Makanae K, Moriya H. Evaluation of the lower protein limit in the budding yeast Saccharomyces cerevisiae using TIPI-gTOW. BMC SYSTEMS BIOLOGY 2014; 8:2. [PMID: 24393197 PMCID: PMC3892067 DOI: 10.1186/1752-0509-8-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 12/27/2013] [Indexed: 12/19/2022]
Abstract
Background Identifying permissible limits of intracellular parameters such as protein expression provides important information for examining robustness. In this study, we used the TEV protease-mediated induction of protein instability (TIPI) in combination with the genetic Tug-of-War (gTOW) to develop a method to measure the lower limit of protein level. We first tested the feasibility of this method using ADE2 as a marker and then analyzed some cell cycle regulators to reveal genetic interactions. Results Using TIPI-gTOW, we successfully constructed a strain in which GFP-TDegFAde2 was expressed at the lower limit, just sufficient to support cellular growth under the -Ade condition by accelerating degradation by TEV protease. We also succeeded in constructing a strain in which the minimal level of GFP-TDegFCdc20 was expressed by TIPI-gTOW. Using this strain, we studied genetic interactions between cell cycle regulators and CDC20, and the result was highly consistent with the previously identified interactions. Comparison of the experimental data with predictions of a mathematical model revealed some interactions that were not implemented into the current model. Conclusions TIPI-gTOW is useful for estimating changes in the lower limit of a protein under different conditions, such as different genetic backgrounds and environments. TIPI-gTOW is also useful for analyzing genetic interactions of essential genes whose deletion mutants cannot be obtained.
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Affiliation(s)
| | | | | | | | | | - Hisao Moriya
- Research Core for Interdisciplinary Sciences, Okayama University, Kita-ku, Okayama, Japan.
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242
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Higher-order septin assembly is driven by GTP-promoted conformational changes: evidence from unbiased mutational analysis in Saccharomyces cerevisiae. Genetics 2014; 196:711-27. [PMID: 24398420 PMCID: PMC3948802 DOI: 10.1534/genetics.114.161182] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Septin proteins bind GTP and heterooligomerize into filaments with conserved functions across a wide range of eukaryotes. Most septins hydrolyze GTP, altering the oligomerization interfaces; yet mutations designed to abolish nucleotide binding or hydrolysis by yeast septins perturb function only at high temperatures. Here, we apply an unbiased mutational approach to this problem. Mutations causing defects at high temperature mapped exclusively to the oligomerization interface encompassing the GTP-binding pocket, or to the pocket itself. Strikingly, cold-sensitive defects arise when certain of these same mutations are coexpressed with a wild-type allele, suggestive of a novel mode of dominance involving incompatibility between mutant and wild-type molecules at the septin–septin interfaces that mediate filament polymerization. A different cold-sensitive mutant harbors a substitution in an unstudied but highly conserved region of the septin Cdc12. A homologous domain in the small GTPase Ran allosterically regulates GTP-binding domain conformations, pointing to a possible new functional domain in some septins. Finally, we identify a mutation in septin Cdc3 that restores the high-temperature assembly competence of a mutant allele of septin Cdc10, likely by adopting a conformation more compatible with nucleotide-free Cdc10. Taken together, our findings demonstrate that GTP binding and hydrolysis promote, but are not required for, one-time events—presumably oligomerization-associated conformational changes—during assembly of the building blocks of septin filaments. Restrictive temperatures impose conformational constraints on mutant septin proteins, preventing new assembly and in certain cases destabilizing existing assemblies. These insights from yeast relate directly to disease-causing mutations in human septins.
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243
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Abstract
Microscopic imaging techniques play a pivotal role in the life sciences. Here we describe labeling and imaging methods for live yeast cell imaging. Yeast is an excellent reference organism for biomedical research to investigate fundamental cellular processes, and has gained great popularity also for large-scale imaging-based screens. Methods are described to label live yeast cells with organelle-specific fluorescent dyes or GFP-tagged proteins, and how cells are maintained viable over extended periods of time during microscopy. We point out common pitfalls and potential microscopy artifacts arising from inhomogeneous labeling and depending on cellular physiology. Application and limitation of bleaching techniques to address dynamic processes in the yeast cell are described.
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Affiliation(s)
- Heimo Wolinski
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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244
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Abstract
Genetic interactions occur when mutant alleles of two or more genes collaborate to generate an unusual composite phenotype, one that would not be predicted based on the expected combined effects of the individual mutant alleles. Synthetic Genetic Array (SGA) methodology was developed to automate yeast genetic analysis and enable systematic genetic interaction studies. In its simplest form, SGA consists of a series of replica pinning steps, which enable the construction of haploid double mutants through mating and meiotic recombination. For example, a strain carrying a query mutation, such as a deletion allele of a nonessential gene or a conditional temperature sensitive allele of an essential gene, could be crossed to an input array of yeast mutants, such as the complete set of ~5,000 viable deletion mutants, to generate an output array of double mutants, that can be scored for genetic interactions based on estimates of cellular fitness derived from colony-size measurements. A simple quantitative measure of genetic interactions can be derived from colony size, which serves as a proxy for fitness. Furthermore, SGA can be applied in a variety of other contexts, such as Synthetic Dosage Lethality (SDL), in which a query mutation is crossed into an array of yeast strains, each of which overexpresses a different gene, thus making use of SGA to probe for gain-of-function phenotypes in specific genetic backgrounds. High-Content Screening (HCS) also integrates SGA to perform genome-wide screens for quantitative analysis of morphological phenotypes or pathway activity based upon fluorescent markers, extending genetic interaction analysis beyond fitness-based measurements. Genetic interaction studies offer insight into gene function, pathway structure, and buffering, and thus a complete genetic interaction network of yeast will generate a global functional wiring diagram for a eukaryotic cell.
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245
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Abstract
In addition to environmental factors and intrinsic variations in base substitution rates, specific genome-destabilizing mutations can shape the mutational trajectory of genomes. How specific alleles influence the nature and position of accumulated mutations in a genomic context is largely unknown. Understanding the impact of genome-destabilizing alleles is particularly relevant to cancer genomes where biased mutational signatures are identifiable. We first created a more complete picture of cellular pathways that impact mutation rate using a primary screen to identify essential Saccharomyces cerevisiae gene mutations that cause mutator phenotypes. Drawing primarily on new alleles identified in this resource, we measure the impact of diverse mutator alleles on mutation patterns directly by whole-genome sequencing of 68 mutation-accumulation strains derived from wild-type and 11 parental mutator genotypes. The accumulated mutations differ across mutator strains, displaying base-substitution biases, allele-specific mutation hotspots, and break-associated mutation clustering. For example, in mutants of POLα and the Cdc13–Stn1–Ten1 complex, we find a distinct subtelomeric bias for mutations that we show is independent of the target sequence. Together our data suggest that specific genome-instability mutations are sufficient to drive discrete mutational signatures, some of which share properties with mutation patterns seen in tumors. Thus, in a population of cells, genome-instability mutations could influence clonal evolution by establishing discrete mutational trajectories for genomes.
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246
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Lenstra TL, Tudek A, Clauder S, Xu Z, Pachis ST, van Leenen D, Kemmeren P, Steinmetz LM, Libri D, Holstege FCP. The role of Ctk1 kinase in termination of small non-coding RNAs. PLoS One 2013; 8:e80495. [PMID: 24324601 PMCID: PMC3851182 DOI: 10.1371/journal.pone.0080495] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022] Open
Abstract
Transcription termination in Saccharomyces cerevisiae can be performed by at least two distinct pathways and is influenced by the phosphorylation status of the carboxy-terminal domain (CTD) of RNA polymerase II (Pol II). Late termination of mRNAs is performed by the CPF/CF complex, the recruitment of which is dependent on CTD-Ser2 phosphorylation (Ser2P). Early termination of shorter cryptic unstable transcripts (CUTs) and small nucleolar/nuclear RNAs (sno/snRNAs) is performed by the Nrd1-Nab3-Sen1 (NNS) complex that binds phosphorylated CTD-Ser5 (Ser5P) via the CTD-interacting domain (CID) of Nrd1p. In this study, mutants of the different termination pathways were compared by genome-wide expression analysis. Surprisingly, the expression changes observed upon loss of the CTD-Ser2 kinase Ctk1p are more similar to those derived from alterations in the Ser5P-dependent NNS pathway, than from loss of CTD-Ser2P binding factors. Tiling array analysis of ctk1Δ cells reveals readthrough at snoRNAs, at many cryptic unstable transcripts (CUTs) and stable uncharacterized transcripts (SUTs), but only at some mRNAs. Despite the suggested predominant role in termination of mRNAs, we observed that a CTK1 deletion or a Pol II CTD mutant lacking all Ser2 positions does not result in a global mRNA termination defect. Rather, termination defects in these strains are widely observed at NNS-dependent genes. These results indicate that Ctk1p and Ser2 CTD phosphorylation have a wide impact in termination of small non-coding RNAs but only affect a subset of mRNA coding genes.
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Affiliation(s)
- Tineke L. Lenstra
- Molecular Cancer Research, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Agnieszka Tudek
- LEA Laboratory of Nuclear RNA Metabolism, Centre de de Génétique Moléculaire, C.N.R.S.-UPR3404, Gif sur Yvette, France
| | - Sandra Clauder
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Zhenyu Xu
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Spyridon T. Pachis
- Molecular Cancer Research, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dik van Leenen
- Molecular Cancer Research, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Patrick Kemmeren
- Molecular Cancer Research, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lars M. Steinmetz
- Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Domenico Libri
- LEA Laboratory of Nuclear RNA Metabolism, Centre de de Génétique Moléculaire, C.N.R.S.-UPR3404, Gif sur Yvette, France
- * E-mail: (DL); (FCPH)
| | - Frank C. P. Holstege
- Molecular Cancer Research, University Medical Center Utrecht, Utrecht, The Netherlands
- * E-mail: (DL); (FCPH)
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247
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Sasvari Z, Gonzalez PA, Rachubinski RA, Nagy PD. Tombusvirus replication depends on Sec39p endoplasmic reticulum-associated transport protein. Virology 2013; 447:21-31. [PMID: 24210096 DOI: 10.1016/j.virol.2013.07.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 07/03/2013] [Accepted: 07/31/2013] [Indexed: 10/26/2022]
Abstract
Positive-stranded RNA viruses subvert subcellular membranes to built viral replicases complexes (VRCs) in infected cells. Tombusviruses use peroxisomal membranes for the assembly of their VRCs and they can efficiently switch to the endoplasmic reticulum membrane in the absence of peroxisomes. In this paper, we show that the ER-resident Sec39p vesicular transport protein is critical for the formation of active VRCs in yeast model host. Repression of Sec39p expression in yeast or in plants resulted in greatly reduced tombusvirus accumulation. Moreover, the purified tombusvirus replicase from Sec39p-depleted yeast cells showed low in vitro activity. Also, tombusvirus RNA replication was poor in cell-free extracts or in isolated ER membranes from yeast with repressed Sec39p expression. The tombusvirus p33 replication protein was mislocalized to the ER when Sec39p was depleted in yeast. Overall, Sec39p is the first peroxisomal biogenesis protein characterized that is critical for tombusvirus replication in yeast and plants.
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Affiliation(s)
- Zsuzsanna Sasvari
- Department of Plant Pathology, University of Kentucky, Lexington, 201F Plant Science Building, KY 40546, USA
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248
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Zhou F, Walker SE, Mitchell SF, Lorsch JR, Hinnebusch AG. Identification and characterization of functionally critical, conserved motifs in the internal repeats and N-terminal domain of yeast translation initiation factor 4B (yeIF4B). J Biol Chem 2013; 289:1704-22. [PMID: 24285537 DOI: 10.1074/jbc.m113.529370] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
eIF4B has been implicated in attachment of the 43 S preinitiation complex (PIC) to mRNAs and scanning to the start codon. We recently determined that the internal seven repeats (of ∼26 amino acids each) of Saccharomyces cerevisiae eIF4B (yeIF4B) compose the region most critically required to enhance mRNA recruitment by 43 S PICs in vitro and stimulate general translation initiation in yeast. Moreover, although the N-terminal domain (NTD) of yeIF4B contributes to these activities, the RNA recognition motif is dispensable. We have now determined that only two of the seven internal repeats are sufficient for wild-type (WT) yeIF4B function in vivo when all other domains are intact. However, three or more repeats are needed in the absence of the NTD or when the functions of eIF4F components are compromised. We corroborated these observations in the reconstituted system by demonstrating that yeIF4B variants with only one or two repeats display substantial activity in promoting mRNA recruitment by the PIC, whereas additional repeats are required at lower levels of eIF4A or when the NTD is missing. These findings indicate functional overlap among the 7-repeats and NTD domains of yeIF4B and eIF4A in mRNA recruitment. Interestingly, only three highly conserved positions in the 26-amino acid repeat are essential for function in vitro and in vivo. Finally, we identified conserved motifs in the NTD and demonstrate functional overlap of two such motifs. These results provide a comprehensive description of the critical sequence elements in yeIF4B that support eIF4F function in mRNA recruitment by the PIC.
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Affiliation(s)
- Fujun Zhou
- From the Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892 and
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249
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Vlasblom J, Jin K, Kassir S, Babu M. Exploring mitochondrial system properties of neurodegenerative diseases through interactome mapping. J Proteomics 2013; 100:8-24. [PMID: 24262152 DOI: 10.1016/j.jprot.2013.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/08/2013] [Accepted: 11/06/2013] [Indexed: 12/20/2022]
Abstract
UNLABELLED Mitochondria are double membraned, dynamic organelles that are required for a large number of cellular processes, and defects in their function have emerged as causative factors for a growing number of human disorders and are highly associated with cancer, metabolic, and neurodegenerative (ND) diseases. Biochemical and genetic investigations have uncovered small numbers of candidate mitochondrial proteins (MPs) involved in ND disease, but given the diversity of processes affected by MP function and the difficulty of detecting interactions involving these proteins, many more likely remain unknown. However, high-throughput proteomic and genomic approaches developed in genetically tractable model prokaryotes and lower eukaryotes have proven to be effective tools for querying the physical (protein-protein) and functional (gene-gene) relationships between diverse types of proteins, including cytosolic and membrane proteins. In this review, we highlight how experimental and computational approaches developed recently by our group and others can be effectively used towards elucidating the mitochondrial interactome in an unbiased and systematic manner to uncover network-based connections. We discuss how the knowledge from the resulting interaction networks can effectively contribute towards the identification of new mitochondrial disease gene candidates, and thus further clarify the role of mitochondrial biology and the complex etiologies of ND disease. BIOLOGICAL SIGNIFICANCE Biochemical and genetic investigations have uncovered small numbers of candidate mitochondrial proteins (MPs) involved in neurodegenerative (ND) diseases, but given the diversity of processes affected by MP function and the difficulty of detecting interactions involving these proteins, many more likely remain unknown. Large-scale proteomic and genomic approaches developed in model prokaryotes and lower eukaryotes have proven to be effective tools for querying the physical (protein-protein) and functional (gene-gene) relationships between diverse types of proteins. Extension of this new framework to the mitochondrial sub-system in human will likewise provide a universally informative systems-level view of the physical and functional landscape for exploring the evolutionary principles underlying mitochondrial function. In this review, we highlight how experimental and computational approaches developed recently by our group and others can be effectively used towards elucidating the mitochondrial interactome in an unbiased and systematic manner to uncover network-based connections. We anticipate that the knowledge from these resulting interaction networks can effectively contribute towards the identification of new mitochondrial disease gene candidates, and thus foster a deeper molecular understanding of mitochondrial biology as well as the etiology of mitochondrial diseases. This article is part of a Special Issue: Can Proteomics Fill the Gap Between Genomics and Phenotypes?
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Affiliation(s)
- James Vlasblom
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Ke Jin
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan S4S 0A2, Canada; Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada; Terrence Donnelly Center for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - Sandy Kassir
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Mohan Babu
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.
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250
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Rochette S, Gagnon-Arsenault I, Diss G, Landry CR. Modulation of the yeast protein interactome in response to DNA damage. J Proteomics 2013; 100:25-36. [PMID: 24262151 DOI: 10.1016/j.jprot.2013.11.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 10/10/2013] [Accepted: 11/05/2013] [Indexed: 01/24/2023]
Abstract
UNLABELLED Cells deploy diverse mechanisms to physiologically adapt to potentially detrimental perturbations. These mechanisms include changes in the organization of protein-protein interaction networks (PINs). Most PINs characterized to date are portrayed in a single environmental condition and are thus likely to miss important connections among biological processes. In this report, we show that the yeast DHFR-PCA on high-density arrays allows to detects modulations of protein-protein interactions (PPIs) in different conditions by testing more than 1000 PPIs in standard and in a drug-inducing DNA damage conditions. We identify 156 PPIs that show significant modulation in response to DNA damage. We provide evidence that modulated PPIs involve essential genes (NOP7, EXO84 and LAS17) playing critical roles in response to DNA damage. Additionally, we show that a significant proportion of PPI changes are likely explained by changes in protein localization and, to a lesser extent, protein abundance. The protein interaction modules affected by changing PPIs support the role of mRNA stability and translation, protein degradation and ubiquitylation and the regulation of the actin cytoskeleton in response to DNA damage. Overall, we provide a valuable tool and dataset for the study of the rewiring of PINs in response to environmental perturbations. BIOLOGICAL SIGNIFICANCE We show that the DHFR-PCA is a high-throughput method that allows the detection of changes in PPIs associated with different environmental conditions using DNA damage response as a testbed. We provide a valuable resource for the study of DNA damage in eukaryotic cells. This article is part of a Special Issue: Can Proteomics Fill the Gap Between Genomics and Phenotypes?
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Affiliation(s)
- Samuel Rochette
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Isabelle Gagnon-Arsenault
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Guillaume Diss
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Christian R Landry
- Département de Biologie, PROTEO and Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, Québec G1V 0A6, Canada.
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