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Cardoso FM, Elias A, Pereira I, Maurício I, Matos O. Improved dsRNA isolation and purification method validated by viral dsRNA detection using novel primers in Saccharomyces cerevisiae. MethodsX 2023; 11:102435. [PMID: 37876828 PMCID: PMC10591000 DOI: 10.1016/j.mex.2023.102435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 10/10/2023] [Indexed: 10/26/2023] Open
Abstract
Accurate genomic sequencing demands high-quality double-stranded RNA (dsRNA). Existing methods for dsRNA extraction from yeast, fungi, and plants primarily rely on cellulose, suitable only for small volume extractions, or the time-consuming lithium chloride precipitation. To streamline the traditional phenol-chloroform-based dsRNA extraction method, the main challenge is the reduction of mitochondrial DNA (mtDNA) and Single Stranded RNA (ssRNA) to no detectable levels after gel electrophoresis. This challenge is successfully addressed through the modified approach described here, involving phenol extraction at low pH, followed by the addition of ammonium sulfate to the aqueous buffer. The dsRNA isolated using this novel method exhibits comparable quality to that obtained through cellulose purification, and it is readily amenable to RT-PCR. Moreover, a single batch of yeast cell RNA isolation requires only 2-3 h of hands-on time, thus simplifying and expediting the process significantly.•Buffers were redesigned from [32,33,35].•No DNASE, Ribonuclease A or beads were used during the purification.•Simple and inexpensive dsRNA extraction and purification method is described.
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Affiliation(s)
- Fernando M.H. Cardoso
- Global Health and Tropical Medicine, GHTM, Associate Laboratory in Translation and Innovation Towards Global Health, LA-REAL, Instituto de Higiene e Medicina Tropical, IHMT, Universidade NOVA de Lisboa, UNL, Rua da Junqueira 100, Lisboa 1349-008, Portugal
| | | | - Inês Pereira
- Global Health and Tropical Medicine, GHTM, Associate Laboratory in Translation and Innovation Towards Global Health, LA-REAL, Instituto de Higiene e Medicina Tropical, IHMT, Universidade NOVA de Lisboa, UNL, Rua da Junqueira 100, Lisboa 1349-008, Portugal
| | - Isabel Maurício
- Global Health and Tropical Medicine, GHTM, Associate Laboratory in Translation and Innovation Towards Global Health, LA-REAL, Instituto de Higiene e Medicina Tropical, IHMT, Universidade NOVA de Lisboa, UNL, Rua da Junqueira 100, Lisboa 1349-008, Portugal
| | - Olga Matos
- Global Health and Tropical Medicine, GHTM, Associate Laboratory in Translation and Innovation Towards Global Health, LA-REAL, Instituto de Higiene e Medicina Tropical, IHMT, Universidade NOVA de Lisboa, UNL, Rua da Junqueira 100, Lisboa 1349-008, Portugal
- Environmental Health Institute, Faculdade de Medicina da Universidade de Lisboa, Lisboa 1649-028, Portugal
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2
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Khalifa ME, MacDiarmid RM. Molecular Characterization of Two Totiviruses from the Commensal Yeast Geotrichum candidum. Viruses 2023; 15:2150. [PMID: 38005831 PMCID: PMC10674808 DOI: 10.3390/v15112150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 10/16/2023] [Accepted: 10/20/2023] [Indexed: 11/26/2023] Open
Abstract
Mycoviruses can infect many of the major taxa of fungi including yeasts. Mycoviruses in the yeast fungus Geotrichum candidum are not well studied with only three G. candidum-associated viral species characterized to date, all of which belong to the Totiviridae genus Totivirus. In this study, we report the molecular characteristics of another two totiviruses co-infecting isolate Gc6 of G. candidum. The two totiviruses were tentatively named Geotrichum candidum totivirus 2 isolate Gc6 (GcTV2-Gc6) and Geotrichum candidum totivirus 4 isolate Gc6 (GcTV4-Gc6). Both viruses have the typical genome organization of totiviruses comprising two ORFs encoding capsid protein (CP) and RNA-dependent RNA polymerase (RdRp) at the N and C termini, respectively. The genomes of GcTV2-Gc6 and GcTV4-Gc6 are 4592 and 4530 bp long, respectively. Both viruses contain the-frameshifting elements and their proteins could be expressed as a single fusion protein. GcTV2-Gc6 is closely related to a totivirus isolated from the same host whereas GcTV4-Gc6 is related to insect-associated totiviruses. The phylogenetic analysis indicated that GcTV2-Gc6 and GcTV4-Gc6 belong to two different sister clades, I-A and I-B, respectively. It is interesting that all viruses identified from G. candidum belong to the genus Totivirus; however, this might be due to the lack of research reporting the characterization of mycoviruses from this fungal host. It is possible that the RNA interference (RNAi) mechanism cannot actively suppress totivirus accumulation in G. candidum Gc6.
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Affiliation(s)
- Mahmoud E. Khalifa
- Botany and Microbiology Department, Faculty of Science, Damietta University, Damietta 34517, Egypt;
| | - Robin M. MacDiarmid
- The New Zealand Institute for Plant and Food Research Limited, Auckland 1025, New Zealand
- School of Biological Sciences, The University of Auckland, Auckland 1010, New Zealand
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3
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Travers-Cook TJ, Jokela J, Buser CC. The evolutionary ecology of fungal killer phenotypes. Proc Biol Sci 2023; 290:20231108. [PMID: 37583325 PMCID: PMC10427833 DOI: 10.1098/rspb.2023.1108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 07/20/2023] [Indexed: 08/17/2023] Open
Abstract
Ecological interactions influence evolutionary dynamics by selecting upon fitness variation within species. Antagonistic interactions often promote genetic and species diversity, despite the inherently suppressive effect they can have on the species experiencing them. A central aim of evolutionary ecology is to understand how diversity is maintained in systems experiencing antagonism. In this review, we address how certain single-celled and dimorphic fungi have evolved allelopathic killer phenotypes that engage in antagonistic interactions. We discuss the evolutionary pathways to the production of lethal toxins, the functions of killer phenotypes and the consequences of competition for toxin producers, their competitors and toxin-encoding endosymbionts. Killer phenotypes are powerful models because many appear to have evolved independently, enabling across-phylogeny comparisons of the origins, functions and consequences of allelopathic antagonism. Killer phenotypes can eliminate host competitors and influence evolutionary dynamics, yet the evolutionary ecology of killer phenotypes remains largely unknown. We discuss what is known and what remains to be ascertained about killer phenotype ecology and evolution, while bringing their model system properties to the reader's attention.
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Affiliation(s)
- Thomas J. Travers-Cook
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
- Department of Aquatic Ecology, Eawag, Dübendorf, Switzerland
| | - Jukka Jokela
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
- Department of Aquatic Ecology, Eawag, Dübendorf, Switzerland
| | - Claudia C. Buser
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
- Department of Aquatic Ecology, Eawag, Dübendorf, Switzerland
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4
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Kireeva N, Galkina K, Sokolov S, Knorre D. Role of Dead Cells in Collective Stress Tolerance in Microbial Communities: Evidence from Yeast. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1528-1534. [PMID: 36717444 DOI: 10.1134/s0006297922120100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
A substantial part of yeast life cycle takes place in the communities where the cells are surrounded by their own clones. Meanwhile, yeast cell fitness depends not only on its own adaptations but also on the processes in the neighboring cells. Moreover, even if a cell loses its clonogenic ability, it is still capable of protecting surrounding cells that are still alive. Dead cells can absorb lipophilic antibiotics and provide nutrients to their kin neighbors. Some enzymes can be released into the environment and detoxify exogenous toxins. For example, cytosolic catalase, which degrades hydrogen peroxide, can stay active outside of the cell. Inviable cells of pathogenic yeast species can suppress host immune responses and, in this way, boost spread of the pathogen. In this review, we speculate that biochemical processes in dying cells can facilitate increase of stress resistance in the alive kin cells and therefore be a subject of natural selection. We considered possible scenarios of how dead microbial cells can increase survival of their kin using unicellular fungi - baker's yeast Saccharomyces cerevisiae - as an example. We conclude that the evolutionary conserved mechanisms of programmed cell death in yeast are likely to include a module of early permeabilization of the cell plasma membrane rather than preserve its integrity.
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Affiliation(s)
- Nataliia Kireeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia. .,Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Kseniia Galkina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Sviatoslav Sokolov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Dmitry Knorre
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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5
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Adaptive Response of Saccharomyces Hosts to Totiviridae L-A dsRNA Viruses Is Achieved through Intrinsically Balanced Action of Targeted Transcription Factors. J Fungi (Basel) 2022; 8:jof8040381. [PMID: 35448612 PMCID: PMC9028071 DOI: 10.3390/jof8040381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 11/17/2022] Open
Abstract
Totiviridae L-A virus is a widespread yeast dsRNA virus. The persistence of the L-A virus alone appears to be symptomless, but the concomitant presence of a satellite M virus provides a killer trait for the host cell. The presence of L-A dsRNA is common in laboratory, industrial, and wild yeasts, but little is known about the impact of the L-A virus on the host’s gene expression. In this work, based on high-throughput RNA sequencing data analysis, the impact of the L-A virus on whole-genome expression in three different Saccharomyces paradoxus and S. cerevisiae host strains was analyzed. In the presence of the L-A virus, moderate alterations in gene expression were detected, with the least impact on respiration-deficient cells. Remarkably, the transcriptional adaptation of essential genes was limited to genes involved in ribosome biogenesis. Transcriptional responses to L-A maintenance were, nevertheless, similar to those induced upon stress or nutrient availability. Based on these data, we further dissected yeast transcriptional regulators that, in turn, modulate the cellular L-A dsRNA levels. Our findings point to totivirus-driven fine-tuning of the transcriptional landscape in yeasts and uncover signaling pathways employed by dsRNA viruses to establish the stable, yet allegedly profitless, viral infection of fungi.
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6
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Chiba Y, Tomaru Y, Shimabukuro H, Kimura K, Hirai M, Takaki Y, Hagiwara D, Nunoura T, Urayama SI. Viral RNA Genomes Identified from Marine Macroalgae and a Diatom. Microbes Environ 2021; 35. [PMID: 32554943 PMCID: PMC7511793 DOI: 10.1264/jsme2.me20016] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Protists provide insights into the diversity and function of RNA viruses in marine systems. Among them, marine macroalgae are good targets for RNA virome analyses because they have a sufficient biomass in nature. However, RNA viruses in macroalgae have not yet been examined in detail, and only partial genome sequences have been reported for the majority of RNA viruses. Therefore, to obtain further insights into the distribution and diversity of RNA viruses associated with marine protists, we herein examined RNA viruses in macroalgae and a diatom. We report the putative complete genome sequences of six novel RNA viruses from two marine macroalgae and one diatom holobiont. Four viruses were not classified into established viral genera or families. Furthermore, a virus classified into Totiviridae showed a genome structure that has not yet been reported in this family. These results suggest that a number of distinct RNA viruses are widespread in a broad range of protists.
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Affiliation(s)
- Yuto Chiba
- Laboratory of Fungal Interaction and Molecular Biology (donated by IFO), Department of Life and Environmental Sciences, University of Tsukuba.,Faculty of Science, International College of Arts and Science, Yokohama City University
| | - Yuji Tomaru
- Japan Fisheries Research and Education Agency, National Research Institute of Fisheries and Environment of the Inland Sea
| | - Hiromori Shimabukuro
- Japan Fisheries Research and Education Agency, National Research Institute of Fisheries and Environment of the Inland Sea
| | | | - Miho Hirai
- Super-cutting-edge Grand and Advanced Research (SUGAR) Program, JAMSTEC
| | - Yoshihiro Takaki
- Super-cutting-edge Grand and Advanced Research (SUGAR) Program, JAMSTEC
| | - Daisuke Hagiwara
- Laboratory of Fungal Interaction and Molecular Biology (donated by IFO), Department of Life and Environmental Sciences, University of Tsukuba.,Microbiology Research Center for Sustainability (MiCS), University of Tsukuba
| | - Takuro Nunoura
- Research Center for Bioscience and Nanoscience (CeBN), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
| | - Syun-Ichi Urayama
- Laboratory of Fungal Interaction and Molecular Biology (donated by IFO), Department of Life and Environmental Sciences, University of Tsukuba.,Microbiology Research Center for Sustainability (MiCS), University of Tsukuba.,Research Center for Bioscience and Nanoscience (CeBN), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
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7
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Analysis of Yeast Killer Toxin K1 Precursor Processing via Site-Directed Mutagenesis: Implications for Toxicity and Immunity. mSphere 2020; 5:5/1/e00979-19. [PMID: 32051241 PMCID: PMC7021474 DOI: 10.1128/msphere.00979-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The killer phenotype in the baker’s yeast Saccharomyces cerevisiae relies on two double-stranded RNA viruses that are persistently present in the cytoplasm. As they carry the same receptor populations as sensitive cells, killer yeast cells need—in contrast to various bacterial toxin producers—a specialized immunity mechanism. The ionophoric killer toxin K1 leads to the formation of cation-specific pores in the plasma membrane of sensitive yeast cells. Based on the data generated in this study, we were able to update the current model of toxin processing, validating the temporary inactivation of the toxic α subunit during maturation in the secretory pathway of the killer yeast. K1 represents a heterodimeric A/B toxin secreted by virus-infected Saccharomyces cerevisiae strains. In a two-staged receptor-mediated process, the ionophoric activity of K1 leads to an uncontrolled influx of protons, culminating in the breakdown of the cellular transmembrane potential of sensitive cells. K1 killer yeast necessitate not only an immunity mechanism saving the toxin-producing cell from its own toxin but, additionally, a molecular system inactivating the toxic α subunit within the secretory pathway. In this study, different derivatives of the K1 precursor were constructed to analyze the biological function of particular structural components and their influence on toxin activity as well as the formation of protective immunity. Our data implicate an inactivation of the α subunit during toxin maturation and provide the basis for an updated model of K1 maturation within the host cell’s secretory pathway. IMPORTANCE The killer phenotype in the baker’s yeast Saccharomyces cerevisiae relies on two double-stranded RNA viruses that are persistently present in the cytoplasm. As they carry the same receptor populations as sensitive cells, killer yeast cells need—in contrast to various bacterial toxin producers—a specialized immunity mechanism. The ionophoric killer toxin K1 leads to the formation of cation-specific pores in the plasma membrane of sensitive yeast cells. Based on the data generated in this study, we were able to update the current model of toxin processing, validating the temporary inactivation of the toxic α subunit during maturation in the secretory pathway of the killer yeast.
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8
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Substitution of cysteines in the yeast viral killer toxin K1 precursor reveals novel insights in heterodimer formation and immunity. Sci Rep 2019; 9:13127. [PMID: 31511600 PMCID: PMC6739482 DOI: 10.1038/s41598-019-49621-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 08/28/2019] [Indexed: 02/07/2023] Open
Abstract
The killer toxin K1 is a virally encoded fungal A/B toxin acting by disrupting plasma membrane integrity. The connection of α and β constitutes a critical feature for toxin biology and for decades the formation of three disulphide bonds linking the major toxin subunits was accepted as status quo. Due to the absence of experimental evidence, the involvement of each cysteine in heterodimer formation, K1 lethality and immunity was systematically analysed. Substitution of any cysteine in α led to a complete loss of toxin dimer secretion and toxicity, whereas K1 toxin derivatives carrying mutations of C248, C312 or the double mutation C248-312 were active against spheroplasted cells. Importantly, substitution of the C95 and C107 in the toxin precursor completely abolished the mediation of functional immunity. In contrast, K1 toxicity, i.e. its ionophoric effect, does not depend on the cysteine residues at all. In contrast to the literature, our data imply the formation of a single disulphide bond involving C92 in α and C239 in β. This finding not only refines the current model stated for decades but also provides new opportunities to elucidate the mechanisms underlying K1 toxicity and immunity at the molecular level.
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9
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Gier S, Simon M, Nordström K, Khalifa S, Schulz MH, Schmitt MJ, Breinig F. Transcriptome Kinetics of Saccharomyces cerevisiae in Response to Viral Killer Toxin K1. Front Microbiol 2019; 10:1102. [PMID: 31156606 PMCID: PMC6531845 DOI: 10.3389/fmicb.2019.01102] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/30/2019] [Indexed: 11/29/2022] Open
Abstract
The K1 A/B toxin secreted by virus-infected Saccharomyces cerevisiae strains kills sensitive cells via disturbance of cytoplasmic membrane functions. Despite decades of research, the mechanisms underlying K1 toxicity and immunity have not been elucidated yet. In a novel approach, this study aimed to characterize transcriptome changes in K1-treated sensitive yeast cells in a time-dependent manner. Global transcriptional profiling revealed substantial cellular adaptations in target cells resulting in 1,189 differentially expressed genes in total. Killer toxin K1 induced oxidative, cell wall and hyperosmotic stress responses as well as rapid down-regulation of transcription and translation. Essential pathways regulating energy metabolism were also significantly affected by the toxin. Remarkably, a futile cycle of the osmolytes trehalose and glycogen was identified probably representing a critical feature of K1 intoxication. In silico analysis suggested several transcription factors involved in toxin-triggered signal transduction. The identified transcriptome changes provide valuable hints to illuminate the still unknown molecular events leading to K1 toxicity and immunity implicating an evolutionarily conserved response at least initially counteracting ionophoric toxin action.
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Affiliation(s)
- Stefanie Gier
- Department of Molecular and Cell Biology, Saarland University, Saarbrücken, Germany.,Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Martin Simon
- Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany.,Molecular Cell Biology and Microbiology, University of Wuppertal, Wuppertal, Germany.,Molecular Cell Dynamics, Saarland University, Saarbrücken, Germany
| | - Karl Nordström
- Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany.,Department of Genetics/Epigenetics, Saarland University, Saarbrücken, Germany
| | - Salem Khalifa
- Cluster of Excellence "Multimodal Computing and Interaction", Max Planck Institute for Informatics, Saarland University, Saarbrücken, Germany
| | - Marcel H Schulz
- Cluster of Excellence "Multimodal Computing and Interaction", Max Planck Institute for Informatics, Saarland University, Saarbrücken, Germany
| | - Manfred J Schmitt
- Department of Molecular and Cell Biology, Saarland University, Saarbrücken, Germany.,Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Frank Breinig
- Department of Molecular and Cell Biology, Saarland University, Saarbrücken, Germany.,Center of Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
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10
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Kyrychenko AN, Tsyganenko KS, Olishevska SV. Hypovirulence of Mycoviruses as a Tool for Biotechnological Control of Phytopathogenic Fungi. CYTOL GENET+ 2018. [DOI: 10.3103/s0095452718050043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Gier S, Schmitt MJ, Breinig F. Expression of K1 Toxin Derivatives in Saccharomyces cerevisiae Mimics Treatment with Exogenous Toxin and Provides a Useful Tool for Elucidating K1 Mechanisms of Action and Immunity. Toxins (Basel) 2017; 9:toxins9110345. [PMID: 29076990 PMCID: PMC5705960 DOI: 10.3390/toxins9110345] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/10/2017] [Accepted: 10/25/2017] [Indexed: 11/25/2022] Open
Abstract
Killer toxin K1 is a heterodimeric protein toxin secreted by Saccharomyces cerevisiae strains infected with the M1 double-stranded RNA ‘killer’ virus. After binding to a primary receptor at the level of the cell wall, K1 interacts with its secondary plasma membrane receptor Kre1p, eventually leading to an ionophoric disruption of membrane function. Although it has been under investigation for decades, neither the particular mechanisms leading to toxicity nor those leading to immunity have been elucidated. In this study, we constructed derivatives of the K1α subunit and expressed them in sensitive yeast cells. We show that these derivatives are able to mimic the action of externally applied K1 toxin in terms of growth inhibition and pore formation within the membrane, leading to a suicidal phenotype that could be abolished by co-expression of the toxin precursor, confirming a mechanistic similarity of external and internal toxin action. The derivatives were successfully used to investigate a null mutant completely resistant to externally applied toxin. They provide a valuable tool for the identification of so far unknown gene products involved in K1 toxin action and/or immunity.
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Affiliation(s)
- Stefanie Gier
- Center for Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbrücken, Germany.
- Molecular and Cell Biology, Campus A1.5, Saarland University, D-66123 Saarbrücken, Germany.
| | - Manfred J Schmitt
- Center for Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbrücken, Germany.
- Molecular and Cell Biology, Campus A1.5, Saarland University, D-66123 Saarbrücken, Germany.
| | - Frank Breinig
- Center for Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbrücken, Germany.
- Molecular and Cell Biology, Campus A1.5, Saarland University, D-66123 Saarbrücken, Germany.
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12
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Becker B, Schmitt MJ. Yeast Killer Toxin K28: Biology and Unique Strategy of Host Cell Intoxication and Killing. Toxins (Basel) 2017; 9:toxins9100333. [PMID: 29053588 PMCID: PMC5666379 DOI: 10.3390/toxins9100333] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 10/12/2017] [Accepted: 10/17/2017] [Indexed: 01/18/2023] Open
Abstract
The initial discovery of killer toxin-secreting brewery strains of Saccharomyces cerevisiae (S. cerevisiae) in the mid-sixties of the last century marked the beginning of intensive research in the yeast virology field. So far, four different S. cerevisiae killer toxins (K28, K1, K2, and Klus), encoded by cytoplasmic inherited double-stranded RNA viruses (dsRNA) of the Totiviridae family, have been identified. Among these, K28 represents the unique example of a yeast viral killer toxin that enters a sensitive cell by receptor-mediated endocytosis to reach its intracellular target(s). This review summarizes and discusses the most recent advances and current knowledge on yeast killer toxin K28, with special emphasis on its endocytosis and intracellular trafficking, pointing towards future directions and open questions in this still timely and fascinating field of killer yeast research.
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Affiliation(s)
- Björn Becker
- Molecular and Cell Biology, Department of Biosciences and Center of Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbrücken, Germany.
| | - Manfred J Schmitt
- Molecular and Cell Biology, Department of Biosciences and Center of Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbrücken, Germany.
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13
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Flores O, Alcaíno J, Fernandez-Lobato M, Cifuentes V, Baeza M. Characterization of virus-like particles and identification of capsid proteins in Xanthophyllomyces dendrorhous. Virus Genes 2015; 50:253-9. [PMID: 25663143 DOI: 10.1007/s11262-015-1171-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 01/09/2015] [Indexed: 11/30/2022]
Abstract
Two dsRNAs of estimated lengths of 5 (L1) and 3.7 (L2) kpb are commonly found in strains of the basidiomycetous yeast Xanthophyllomyces dendrorhous, and the presence of virus-like particles (VLPs) have been described in some strains. Recently, two putative totiviruses (XdV-L1A and XdV-L1B) were identified from L1 dsRNA and one (XdV-L2) from L2 dsRNA in the strain UCD 67-385. In some strains, there are smaller dsRNAs (0.9-1.4 kb) that probable are satellite elements. In this work, the VLPs from several strains of X. dendrorhous, which differ in their dsRNAs content, were separated by sucrose gradient and characterized in relation to the dsRNAs and proteins that compose them. It was found that all types of dsRNAs were encapsidated into VLPs, supporting the hypothesis that the smaller dsRNAs are satellite molecules. A main protein of approx. 76 or 37 kDa composed the virions that only have the L1-dsRNA or L2-dsRNA, respectively. In the strain UCD 67-385, these both proteins were identified as viral capsid protein (CP), allow to confirm the gag predicted ORFs in XdV-L1A, XdV-L1B, and XdV-L2, with CPs of 76.6, 76.2, and 38.8 kDa, respectively. Analysis of predicted structures of CPs of XdV-L1A and XdV-L1B, showed high similitudes with the CPs of ScV-L-A and other totiviruses.
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Affiliation(s)
- Oriana Flores
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago, Chile,
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14
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Saberi S, Cliff MA, van Vuuren HJJ. Comparison of Genetic and Enological Characteristics of New and ExistingS. cerevisiaeStrains for Chardonnay Wine Fermentations. FOOD BIOTECHNOL 2014. [DOI: 10.1080/08905436.2014.931863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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15
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Baeza M, Bravo N, Sanhueza M, Flores O, Villarreal P, Cifuentes V. Molecular characterization of totiviruses in Xanthophyllomyces dendrorhous. Virol J 2012; 9:140. [PMID: 22838956 PMCID: PMC3561658 DOI: 10.1186/1743-422x-9-140] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 07/17/2012] [Indexed: 12/12/2022] Open
Abstract
Background Occurrence of extrachromosomal dsRNA elements has been described in the red-yeast Xanthophyllomyces dendrorhous, with numbers and sizes that are highly variable among strains with different geographical origin. The studies concerning to the encapsidation in viral-like particles and dsRNA-curing have suggested that some dsRNAs are helper viruses, while others are satellite viruses. However, the nucleotide sequences and functions of these dsRNAs are still unknown. In this work, the nucleotide sequences of four dsRNAs of the strain UCD 67–385 of X. dendrorhous were determined, and their identities and genome structures are proposed. Based on this molecular data, the dsRNAs of different strains of X. dendrorhous were analyzed. Results The complete sequences of L1, L2, S1 and S2 dsRNAs of X. dendrorhous UCD 67–385 were determined, finding two sequences for L1 dsRNA (L1A and L1B). Several ORFs were uncovered in both S1 and S2 dsRNAs, but no homologies were found for any of them when compared to the database. Instead, two ORFs were identified in each L1A, L1B and L2 dsRNAs, whose deduced amino acid sequences were homologous with a major capsid protein (5’-ORF) and a RNA-dependent RNA polymerase (3’-ORF) belonging to the Totiviridae family. The genome structures of these dsRNAs are characteristic of Totiviruses, with two overlapped ORFs (the 3’-ORF in the −1 frame with respect to the 5’-ORF), with a slippery site and a pseudoknot in the overlapped regions. These structures are essential for the synthesis of the viral polymerase as a fusion protein with the viral capsid protein through −1 ribosomal frameshifting. In the RNase protection analysis, all the dsRNAs in the four analyzed X. dendrorhous strains were protected from enzymatic digestion. The RT-PCR analysis revealed that, similar to strain UCD 67–385, the L1A and L1B dsRNAs coexist in the strains VKM Y-2059, UCD 67–202 and VKM Y-2786. Furthermore, determinations of the relative amounts of L1 dsRNAs using two-step RT-qPCR revealed a 40-fold increment of the ratio L1A/L1B in the S2 dsRNA-cured strain compared to its parental strain. Conclusions Three totiviruses, named as XdV-L1A, XdV-L1B and XdV-L2, were identified in the strain UCD 67–385 of X. dendrorhous. The viruses XdV-L1A and XdV-L1B were also found in other three X. dendrorhous strains. Our results suggest that the smaller dsRNAs (named XdRm-S1 and XdRm-S2) of strain UCD 67–385 are satellite viruses, and particularly that XdRm-S2 is a satellite of XdV-L1A.
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Affiliation(s)
- Marcelo Baeza
- Departamento de Ciencias Ecológicas, Laboratorio de Genética, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago, Chile.
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Göker M, Scheuner C, Klenk HP, Stielow JB, Menzel W. Codivergence of mycoviruses with their hosts. PLoS One 2011; 6:e22252. [PMID: 21829452 PMCID: PMC3146478 DOI: 10.1371/journal.pone.0022252] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 06/17/2011] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The associations between pathogens and their hosts are complex and can result from any combination of evolutionary events such as codivergence, switching, and duplication of the pathogen. Mycoviruses are RNA viruses which infect fungi and for which natural vectors are so far unknown. Thus, lateral transfer might be improbable and codivergence their dominant mode of evolution. Accordingly, mycoviruses are a suitable target for statistical tests of virus-host codivergence, but inference of mycovirus phylogenies might be difficult because of low sequence similarity even within families. METHODOLOGY We analyzed here the evolutionary dynamics of all mycovirus families by comparing virus and host phylogenies. Additionally, we assessed the sensitivity of the co-phylogenetic tests to the settings for inferring virus trees from their genome sequences and approximate, taxonomy-based host trees. CONCLUSIONS While sequence alignment filtering modes affected branch support, the overall results of the co-phylogenetic tests were significantly influenced only by the number of viruses sampled per family. The trees of the two largest families, Partitiviridae and Totiviridae, were significantly more similar to those of their hosts than expected by chance, and most individual host-virus links had a significant positive impact on the global fit, indicating that codivergence is the dominant mode of virus diversification. However, in this regard mycoviruses did not differ from closely related viruses sampled from non-fungus hosts. The remaining virus families were either dominated by other evolutionary modes or lacked an apparent overall pattern. As this negative result might be caused by insufficient taxon sampling, the most parsimonious hypothesis still is that host-parasite evolution is basically the same in all mycovirus families. This is the first study of mycovirus-host codivergence, and the results shed light not only on how mycovirus biology affects their co-phylogenetic relationships, but also on their presumable host range itself.
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Affiliation(s)
- Markus Göker
- DSMZ-German Collection for Microorganisms and Cell Cultures, Braunschweig, Germany.
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17
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The inter-generic fungicidal activity of Xanthophyllomyces dendrorhous. J Microbiol 2011; 48:822-8. [PMID: 21221941 DOI: 10.1007/s12275-010-0180-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 08/22/2010] [Indexed: 10/18/2022]
Abstract
In this study, the existence of intra-specific and inter-generic fungicidal activity in Xanthophyllomyces dendrorhous and Phaffia rhodozyma strains isolated from different regions of the earth was examined. Assays were performed under several culture conditions, showing that all the analyzed X. dendrorhous and P. rhodozyma strains have killing activity against Kloeckera apiculata, Rhodotorula sloffiae, and R. minuta. This activity was greater in rich media at a pH from 4.6 to 5.0. Extracellular protein extracts with fungicidal activity were obtained from cultures of all strains, and their characterization suggested that a protein of 33 kDa is the antifungal factor. According to peptide mass fingerprinting and an analysis of the results with the MASCOT search engine, this protein was identified as an aspartic protease. Additionally, extrachromosomal double-stranded DNA elements (dsDNAs) were observed in all X. dendrorhous and P. rhodozyma strains. Although there is a high variability, two dsDNAs of 5.4 and 6.8 kb are present in all strains.
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Baeza M, Sanhueza M, Flores O, Oviedo V, Libkind D, Cifuentes V. Polymorphism of viral dsRNA in Xanthophyllomyces dendrorhous strains isolated from different geographic areas. Virol J 2009; 6:160. [PMID: 19814805 PMCID: PMC2764699 DOI: 10.1186/1743-422x-6-160] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 10/08/2009] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Strains of the astaxanthin producing yeast Xanthophyllomyces dendrorhous have been isolated from different cold regions around the earth, and the presence of double stranded RNA (dsRNA) elements was described in some isolates. This kind of viruses is widely distributed among yeasts and filamentous fungi and, although generally are cryptic in function, their studies have been a key factor in the knowledge of important fungi. In this work, the characterization and genetic relationships among dsRNA elements were determined in strains representatives of almost all regions of the earth where X. dendrorhous have been isolated. RESULTS Almost all strains of X. dendrorhous analyzed carry one, two or four dsRNA elements, of molecular sizes in the range from 0.8 to 5.0 kb. Different dsRNA-patterns were observed in strains with different geographic origin, being L1 (5.0 kb) the common dsRNA element. By hybridization assays a high genomic polymorphism was observed among L1 dsRNAs of different X. dendrorhous strains. Contrary, hybridization was observed between L1 and L2 dsRNAs of strains from same or different regions, while the dsRNA elements of minor sizes (M, S1, and S2) present in several strains did not show hybridization with neither L1 or L2 dsRNAs. Along the growth curve of UCD 67-385 (harboring four dsRNAs) an increase of L2 relative to L1 dsRNA was observed, while the S1/L1 ratio remains constant, as well as the M/L1 ratio of Patagonian strain. Strains cured of S2 dsRNA were obtained by treatment with anisomycin, and comparison of its dsRNA contents with uncured strain, revealed an increase of L1 dsRNA while the L2 and S1 dsRNA remain unaltered. CONCLUSION The dsRNA elements of X. dendrorhous are highly variable in size and sequence, and the dsRNA pattern is specific to the geographic region of isolation. Each L1 and L2 dsRNA are viral elements able to self replicate and to coexist into a cell, and L1 and S2 dsRNAs elements could be part of a helper/satellite virus system in X. dendrorhous.
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Affiliation(s)
- Marcelo Baeza
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Mario Sanhueza
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Oriana Flores
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Vicente Oviedo
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Diego Libkind
- Laboratorio de Microbiología Aplicada y Biotecnología. Bariloche, Río Negro, Argentina
| | - Víctor Cifuentes
- Laboratorio de Genética, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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Schmitt MJ, Reiter J. Viral induced yeast apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1413-7. [DOI: 10.1016/j.bbamcr.2008.01.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 01/17/2008] [Accepted: 01/18/2008] [Indexed: 11/17/2022]
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Valis K, Masek T, Novotná D, Pospísek M, Janderová B. Immunity to killer toxin K1 is connected with the Golgi-to-vacuole protein degradation pathway. Folia Microbiol (Praha) 2006; 51:196-202. [PMID: 17004650 DOI: 10.1007/bf02932122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Killer strains of Saccharomyces cerevisiae producing killer toxin K1 kill sensitive cells but are resistant to their own toxin. It is assumed that in the producer, an effective interaction between the external toxin and its plasma membrane receptor or the final effector is not possible on the grounds of a conformation change of the receptor or its absence in a membrane. Therefore, it is possible that some mutants with defects in intracellular protein transport and degradation can show a suicidal phenotype during K1 toxin production. We have examined these mutants in a collection of S. cerevisiae strains with deletions in various genes transformed by the pYX213+M1 vector carrying cDNA coding for the K1 toxin under the control of the GAL1 promoter. Determination of the quantity of dead cells in colony population showed that (1) the toxin production from the vector did not support full immunity of producing cells, (2) the suicidal phenotype was not connected with a defect in endocytosis or autophagy, (3) deletants in genes VPS1, VPS23, VPS51 and VAC8 required for the protein degradation pathway between the Golgi body and the vacuole exhibited the highest mortality. These results suggest that interacting molecule(s) on the plasma membrane in the producer might be diverted from the secretion pathway to degradation in the vacuole.
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Affiliation(s)
- K Valis
- Department of Genetics and Microbiology, Faculty ofScience, Charles University, 128 44 Prague, Czechia
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Miyamoto M, Onozato N, Selvakumar D, Kimura T, Furuichi Y, Komiyama T. The role of the histidine-35 residue in the cytocidal action of HM-1 killer toxin. Microbiology (Reading) 2006; 152:2951-2958. [PMID: 17005976 DOI: 10.1099/mic.0.29100-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Diethylpyrocarbonate modification and site-directed mutagenesis studies of histidine-35 in HM-1 killer toxin (HM-1) have shown that a specific feature, the imidazole side chain of histidine-35, is essential for the expression of the killing activity. In subcellular localization experiments, wild-type HM-1 was in the membrane fraction of Saccharomyces cerevisiae BJ1824, but not the HM-1 analogue in which histidine-35 was replaced by alanine (H35A HM-1). Neither wild-type nor H35A HM-1 was detected in cellular fractions of HM-1-resistant yeast S. cerevisiae BJ1824 rhk1Δ : : URA3 and HM-1-insensitive yeast Candida albicans even after 1 h incubation. H35A HM-1 inhibited the activity of partially purified 1,3-β-glucan synthase from S. cerevisiae A451, and its extent was almost the same as wild-type HM-1. Co-immunoprecipitation experiments showed that wild-type and H35A HM-1 directly interact with the 1,3-β-glucan synthase complex. These results strongly suggest that histidine-35 has an important role in the cytocidal action of HM-1 that participates in the binding process to the HM-1 receptor protein on the cell membrane, but it is not essential for the interaction with, and inhibition of, 1,3-β-glucan synthase.
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Affiliation(s)
- Masahiko Miyamoto
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashizima, Niigata 956-8603, Japan
| | - Naohiko Onozato
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashizima, Niigata 956-8603, Japan
| | - Dakshnamurthy Selvakumar
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashizima, Niigata 956-8603, Japan
| | - Tetsuya Kimura
- Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan
| | | | - Tadazumi Komiyama
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1 Higashizima, Niigata 956-8603, Japan
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22
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Danthi P, Hansberger MW, Campbell JA, Forrest JC, Dermody TS. JAM-A-independent, antibody-mediated uptake of reovirus into cells leads to apoptosis. J Virol 2006; 80:1261-70. [PMID: 16415003 PMCID: PMC1346953 DOI: 10.1128/jvi.80.3.1261-1270.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Apoptosis plays a major role in the cytopathic effect induced by reovirus following infection of cultured cells and newborn mice. Strain-specific differences in the capacity of reovirus to induce apoptosis segregate with the S1 and M2 gene segments, which encode attachment protein sigma1 and membrane penetration protein mu1, respectively. Virus strains that bind to both junctional adhesion molecule-A (JAM-A) and sialic acid are the most potent inducers of apoptosis. In addition to receptor binding, events in reovirus replication that occur during or after viral disassembly but prior to initiation of viral RNA synthesis also are required for reovirus-induced apoptosis. To determine whether reovirus infection initiated in the absence of JAM-A and sialic acid results in apoptosis, Chinese hamster ovary (CHO) cells engineered to express Fc receptors were infected with reovirus using antibodies directed against viral outer-capsid proteins. Fc-mediated infection of CHO cells induced apoptosis in a sigma1-independent manner. Apoptosis following this uptake mechanism requires acid-dependent proteolytic disassembly, since treatment of cells with the weak base ammonium chloride diminished the apoptotic response. Analysis of T1L x T3D reassortant viruses revealed that the mu1-encoding M2 gene segment is the only viral determinant of the apoptosis-inducing capacity of reovirus when infection is initiated via Fc receptors. Additionally, a temperature-sensitive, membrane penetration-defective M2 mutant, tsA279.64, is an inefficient inducer of apoptosis. These data suggest that signaling pathways activated by binding of sigma1 to JAM-A and sialic acid are dispensable for reovirus-mediated apoptosis and that the mu1 protein plays an essential role in stimulating proapoptotic signaling.
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Affiliation(s)
- Pranav Danthi
- Department of Pediatrics, and Elizabeth B. Lamb Center for Pediatric Research, D7235 MCN, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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Breinig F, Sendzik T, Eisfeld K, Schmitt MJ. Dissecting toxin immunity in virus-infected killer yeast uncovers an intrinsic strategy of self-protection. Proc Natl Acad Sci U S A 2006; 103:3810-5. [PMID: 16505373 PMCID: PMC1533781 DOI: 10.1073/pnas.0510070103] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Toxin-secreting "killer" yeasts were initially identified >40 years ago in Saccharomyces cerevisiae strains infected with a double-stranded RNA "killer" virus. Despite extensive research conducted on yeast killer toxins, the mechanism of protecting immunity by which toxin-producing cells evade the lethal activities of these proteins has remained elusive. Here, we identify the mechanism leading to protecting immunity in a killer yeast secreting a viral alpha/beta protein toxin (K28) that enters susceptible cells by receptor-mediated endocytosis and, after retrograde transport into the cytosol, blocks DNA synthesis, resulting in both cell-cycle arrest and caspase-mediated apoptosis. We demonstrate that toxin immunity is effected within the cytosol of a toxin-secreting yeast and occurs via the formation of complexes between reinternalized toxin and unprocessed precursor moieties that are subsequently ubiquitinated and proteasomally degraded, eliminating the active form of the toxin. Interference with cellular ubiquitin homeostasis, either through overexpression of mutated ubiquitin (Ub-RR(48/63)) or by blocking deubiquitination, prevents ubiquitination of toxin and results in an impaired immunity and the expression of a suicidal phenotype. The results presented here reveal the uniquely elegant and efficient strategy that killer cells have developed to circumvent the lethal effects of the toxin they produce.
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Affiliation(s)
- Frank Breinig
- Angewandte Molekularbiologie, Universität des Saarlandes, D-66041 Saarbrücken, Germany
| | - Tanja Sendzik
- Angewandte Molekularbiologie, Universität des Saarlandes, D-66041 Saarbrücken, Germany
| | - Katrin Eisfeld
- Angewandte Molekularbiologie, Universität des Saarlandes, D-66041 Saarbrücken, Germany
| | - Manfred J. Schmitt
- Angewandte Molekularbiologie, Universität des Saarlandes, D-66041 Saarbrücken, Germany
- To whom correspondence should be addressed at:
Angewandte Molekularbiologie, FR 8.3, Gebäude A 1.5, Universität des Saarlandes, Postfach 151150, D-66041 Saarbrücken, Germany. E-mail:
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Reiter J, Herker E, Madeo F, Schmitt MJ. Viral killer toxins induce caspase-mediated apoptosis in yeast. ACTA ACUST UNITED AC 2005; 168:353-8. [PMID: 15668299 PMCID: PMC2171720 DOI: 10.1083/jcb.200408071] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In yeast, apoptotic cell death can be triggered by various factors such as H2O2, cell aging, or acetic acid. Yeast caspase (Yca1p) and cellular reactive oxygen species (ROS) are key regulators of this process. Here, we show that moderate doses of three virally encoded killer toxins (K1, K28, and zygocin) induce an apoptotic yeast cell response, although all three toxins differ significantly in their primary killing mechanisms. In contrast, high toxin concentrations prevent the occurrence of an apoptotic cell response and rather cause necrotic, toxin-specific cell killing. Studies with Δyca1 and Δgsh1 deletion mutants indicate that ROS accumulation as well as the presence of yeast caspase 1 is needed for apoptosis in toxin-treated yeast cells. We conclude that in the natural environment of toxin-secreting killer yeasts, where toxin concentration is usually low, induction of apoptosis might play an important role in efficient toxin-mediated cell killing.
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Affiliation(s)
- Jochen Reiter
- Applied Molecular Biology, University of the Saarland, D-66041 Saarbrücken, Germany
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Abstract
Since the initial discovery of the yeast killer system almost 40 years ago, intensive studies have substantially strengthened our knowledge in many areas of biology and provided deeper insights into basic aspects of eukaryotic cell biology as well as into virus-host cell interactions and general yeast virology. Analysis of killer toxin structure, synthesis and secretion has fostered understanding of essential cellular mechanisms such as post-translational prepro-protein processing in the secretory pathway. Furthermore, investigation of the receptor-mediated mode of toxin action proved to be an effective means for dissecting the molecular structure and in vivo assembly of yeast and fungal cell walls, providing important insights relevant to combating infections by human pathogenic yeasts. Besides their general importance in understanding eukaryotic cell biology, killer yeasts, killer toxins and killer viruses are also becoming increasingly interesting with respect to possible applications in biomedicine and gene technology. This review will try to address all these aspects.
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Affiliation(s)
- Manfred J Schmitt
- Angewandte Molekularbiologie (FR 8.3 -- Mikrobiologie), Universität des Saarlandes, Im Stadtwald, Gebäude 2, D-66123 Saarbrücken, Germany.
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Golubev WI, Pfeiffer I, Golubeva E. Mycocin production in Trichosporon pullulans populations colonizing tree exudates in the spring. FEMS Microbiol Ecol 2002; 40:151-7. [DOI: 10.1111/j.1574-6941.2002.tb00947.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Riffer F, Eisfeld K, Breinig F, Schmitt MJ. Mutational analysis of K28 preprotoxin processing in the yeast Saccharomyces cerevisiae. MICROBIOLOGY (READING, ENGLAND) 2002; 148:1317-28. [PMID: 11988505 DOI: 10.1099/00221287-148-5-1317] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
K28 killer strains of Saccharomyces cerevisiae are permanently infected with a cytoplasmic persisting dsRNA virus encoding a secreted alpha/beta heterodimeric protein toxin that kills sensitive cells by cell-cycle arrest and inhibition of DNA synthesis. In vivo processing of the 345 aa toxin precursor (preprotoxin; pptox) involves multiple internal and carboxy-terminal cleavage events by the prohormone convertases Kex2p and Kex1p. By site-directed mutagenesis of the preprotoxin gene and phenotypic analysis of its in vivo effects it is now demonstrated that secretion of a biological active virus toxin requires signal peptidase cleavage after Gly(36) and Kex2p-mediated processing at the alpha subunit N terminus (after Glu-Arg(49)), the alpha subunit C terminus (after Ser-Arg(149)) and at the beta subunit N terminus (after Lys-Arg(245)). The mature C terminus of the beta subunit is trimmed by Kex1p, which removes the terminal Arg(345) residue, thus uncovering the toxin's endoplasmic reticulum targeting signal (HDEL) which--in a sensitive target cell--is essential for retrograde toxin transport. Interestingly, both toxin subunits are covalently linked by a single disulfide bond between alpha-Cys(56) and beta-Cys(340), and expression of a mutant toxin in which beta-Cys(340) had been replaced by Ser(340) resulted in the secretion of a non-toxic alpha/beta heterodimer that is blocked in retrograde transport and incapable of entering the yeast cell cytosol, indicating that one important in vivo function of beta-Cys(340) might be to ensure accessibility of the toxin's beta subunit C terminus to the HDEL receptor of the target cell.
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Affiliation(s)
- Frank Riffer
- Angewandte Molekularbiologie, Universität des Saarlandes, FR 8.3, Gebäude 2, Postfach 151150, D-66041 Saarbrücken, Germany
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28
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Tipper DJ, Harley CA. Yeast genes controlling responses to topogenic signals in a model transmembrane protein. Mol Biol Cell 2002; 13:1158-74. [PMID: 11950929 PMCID: PMC102259 DOI: 10.1091/mbc.01-10-0488] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Yeast protein insertion orientation (PIO) mutants were isolated by selecting for growth on sucrose in cells in which the only source of invertase is a C-terminal fusion to a transmembrane protein. Only the fraction with an exocellular C terminus can be processed to secreted invertase and this fraction is constrained to 2-3% by a strong charge difference signal. Identified pio mutants increased this to 9-12%. PIO1 is SPF1, encoding a P-type ATPase located in the endoplasmic reticulum (ER) or Golgi. spf1-null mutants are modestly sensitive to EGTA. Sensitivity is considerably greater in an spf1 pmr1 double mutant, although PIO is not further disturbed. Pmr1p is the Golgi Ca(2+) ATPase and Spf1p may be the equivalent ER pump. PIO2 is STE24, a metalloprotease anchored in the ER membrane. Like Spf1p, Ste24p is expressed in all yeast cell types and belongs to a highly conserved protein family. The effects of ste24- and spf1-null mutations on invertase secretion are additive, cell generation time is increased 60%, and cells become sensitive to cold and to heat shock. Ste24p and Rce1p cleave the C-AAX bond of farnesylated CAAX box proteins. The closest paralog of SPF1 is YOR291w. Neither rce1-null nor yor291w-null mutations affected PIO or the phenotype of spf1- or ste24-null mutants. Mutations in PIO3 (unidentified) cause a weaker Pio phenotype, enhanced by a null mutation in BMH1, one of two yeast 14-3-3 proteins.
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Affiliation(s)
- Donald J Tipper
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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Abstract
Saccharomyces cerevisiae K1 killer strains are infected by the M1 double-stranded RNA virus encoding a secreted protein toxin that kills sensitive cells by disrupting cytoplasmic membrane function. Toxin binding to spheroplasts is mediated by Kre1p, a cell wall protein initially attached to the plasma membrane by its C-terminal GPI anchor. Kre1p binds toxin directly. Both cells and spheroplasts of Deltakre1 mutants are completely toxin resistant; binding to cell walls and spheroplasts is reduced to 10% and < 0.5%, respectively. Expression of K28-Kre1p, an inactive C-terminal fragment of Kre1p retaining its toxin affinity and membrane anchor, fully restored toxin binding and sensitivity to spheroplasts, while intact cells remained resistant. Kre1p is apparently the toxin membrane receptor required for subsequent lethal ion channel formation.
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Affiliation(s)
- Frank Breinig
- Angewandte Molekularbiologie, Universität des Saarlandes, D-66041, Saarbrücken, Germany
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Suzuki C, Ando Y, Machida S. Interaction of SMKT, a killer toxin produced by Pichia farinosa, with the yeast cell membranes. Yeast 2001; 18:1471-8. [PMID: 11748724 DOI: 10.1002/yea.791] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
SMKT (salt-mediated killer toxin), a killer toxin produced by the halotolerant yeast, Pichia farinosa, kills yeasts of several genera, including Saccharomyces cerevisiae. To elucidate the killing mechanism of SMKT, we examined the interaction of SMKT with membranes using liposomes. Leakage of calcein from calcein-entrapped liposomes was observed in the presence of SMKT. Destruction of liposomes was observed by dark-field microscopy. Comparison of intact S. cerevisiae cells with SMKT-treated cells by dark-field microscopy indicated that the spherical cell membrane is disrupted by SMKT. Using sodium carbonate extraction, we obtained direct evidence for the first time that SMKT is associated with the membrane of sensitive cells. Our results indicate that SMKT kills sensitive S. cerevisiae by interacting with the yeast cell membrane.
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Affiliation(s)
- C Suzuki
- National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
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31
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Eisfeld K, Riffer F, Mentges J, Schmitt MJ. Endocytotic uptake and retrograde transport of a virally encoded killer toxin in yeast. Mol Microbiol 2000; 37:926-40. [PMID: 10972812 DOI: 10.1046/j.1365-2958.2000.02063.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We demonstrate that a virally encoded yeast 'killer' toxin is entering its eukaryotic target cell by endocytosis, subsequently travelling the yeast secretory pathway in reverse to exhibit its lethal effect. The K28 killer toxin is a secreted alpha/beta heterodimer that kills sensitive yeasts in a receptor-mediated fashion by blocking DNA synthesis in the nucleus. In vivo processing of the toxin precursor results in a protein whose beta-C-terminus carries the endoplasmic reticulum (ER) retention signal HDEL, which, as we show here, is essential for retrograde toxin transport. Yeast end3/4 mutants as well as cells lacking the HDEL receptor (Deltaerd2) or mutants defective in Golgi-to-ER protein recycling (erd1) are toxin resistant because the toxin can no longer enter and/or retrograde pass the cell. Site-directed mutagenesis further indicated that the toxin's beta-HDEL motif ensures retrograde transport, although in a toxin-secreting yeast the beta-C-terminus is initially masked by an R residue (beta-HDELR) until Kex1p cleavage uncovers the toxin's targeting signal in a late Golgi compartment. Prevention of Kex1p processing results in high-level secretion of a biologically inactive protein incapable of re-entering the secretory pathway. Finally, we present evidence that ER-to-cytosol toxin export is mediated by the Sec61p translocon and requires functional copies of the lumenal ER chaperones Kar2p and Cne1p.
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Affiliation(s)
- K Eisfeld
- Angewandte Molekularbiologie, Universität des Saarlandes, Germany
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32
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Musmanno RA, Coratza G. Studies on strong and weak killer phenotypes of wine yeasts: production, activity of toxin in must, and its effect in mixed culture fermentation. J Appl Microbiol 1999; 87:932-938. [PMID: 10692075 DOI: 10.1046/j.1365-2672.1999.00954.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two different killer phenotypes were detected among K+ (killer) yeasts isolated from spontaneous wine fermentations using a plate bioassay. The two phenotypes differed in their degree of killer activity, and were designated as SK+(strong killer) and WK+(weak killer). Strains showing either phenotype were assayed for expression of killer activity under different growth conditions. Growth in must negatively affected expression of the killer activity of both phenotypes. The supernatant fluids from must cultures showed a lower killing effect than those from yeast phosphate dextrose broth (YPDB) cultures. The ability of the two K+ phenotypes to prevail on K-sensitive yeasts was studied in mixed-culture fermentation experiments. Under these conditions, only strains showing SK+ phenotype were able to prevail on the K-sensitive yeasts. These results suggest that the K+ phenotype could play a relevant role in spontaneous fermentations provided that the strain exhibits an SK+ phenotype, and that the latter phenotype should be preferred when selected K + strains are to be used as fermentation starters.
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Affiliation(s)
- RA Musmanno
- Dipartimento di Biologia Molecolare - Sezione di Microbiologia, Università degli Studi di Siena, Siena, Italy
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33
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Suzuki C, Shimma YI. P-type ATPase spf1 mutants show a novel resistance mechanism for the killer toxin SMKT. Mol Microbiol 1999; 32:813-23. [PMID: 10361284 DOI: 10.1046/j.1365-2958.1999.01400.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SMKT, a killer toxin produced by the halotolerant yeast Pichia farinosa KK1, consists of alpha and beta subunits with folding remarkably similar to that of the fungal killer toxin KP4, a Ca2+ channel inhibitor. The budding yeast Saccharomyces cerevisiae is sensitive to SMKT. To understand the killing mechanism of SMKT, we isolated SMKT-resistant mutants of S. cerevisiae and characterized them. Five spf mutants (sensitivity to the P. farinosa killer toxin) fell into a single genetic complementation group, designated spf1. The SPF1 gene was cloned by complementation of the mutant phenotype. The SPF1 gene encodes a putative P-type ATPase of 1215 amino acid residues that contains 12 membrane-spanning regions. Gene disruption revealed that the SPF1 gene is not essential for viability but is required for the sensitivity to SMKT. The spf1 disruptant showed some phenotypes characteristic of glycosylation-defective mutants and secreted underglycosylated invertase. Fluorescence-activated cell-sorting analysis and indirect immunofluorescence microscopy showed that SMKT interacts with the cell surface of the resistant cells but not with that of sensitive cells, suggesting a novel resistance mechanism for this toxin. The glycosylation-defective phenotype and possible killer-resistant mechanisms are discussed in comparison with the Golgi Ca2+ pump Pmr1p.
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Affiliation(s)
- C Suzuki
- National Food Research Institute, 2-1-2 Kannon-dai, Tsukuba-shi, Ibaraki-ken, 305-8642 Japan.
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34
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Gerads M, Ernst JF. Overlapping coding regions and trancriptional units of two essential chromosomal genes (CCT8, TRP1)in the fungal pathogen Candida albicans. Nucleic Acids Res 1998; 26:5061-6. [PMID: 9801300 PMCID: PMC147973 DOI: 10.1093/nar/26.22.5061] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Sequencing of the 3'-untranslated region of the CCT8 gene of the fungal pathogen Candida albicans revealed that the CCT8 coding region overlaps 13 bp with the coding region of the convergently orientated TRP1 gene. The same overlap was found in three strains with different genetic backgrounds. 3'-RACE was used to determine that the CCT8 and TRP1 transcripts extended significantly into the coding region of the adjacent gene, which also contained sequences encoding the poly(A) addition site. A strain retaining one wild-type CCT8/TRP1 locus on one chromosome and a deletion on the other homologous chromosome contained both CCT8 and TRP1 transcripts; this result indicates that both transcripts are synthesized from the same gene locus. The CCT8/TRP1 gene pair of C . albicans constitutes an extreme natural case of transcriptional overlap in a eukaryote. The results confirm that convergent overlapping transcription units are compatible with expression of the overlapping genes.
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Affiliation(s)
- M Gerads
- Institut für Mikrobiologie and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine-Universität, Universitätsstrasse 1/26.12, D-40225 Düsseldorf, Germany
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35
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Schmitt MJ, Poravou O, Trenz K, Rehfeldt K. Unique double-stranded RNAs responsible for the anti-Candida activity of the yeast Hanseniaspora uvarum. J Virol 1997; 71:8852-5. [PMID: 9343246 PMCID: PMC192352 DOI: 10.1128/jvi.71.11.8852-8855.1997] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Killer strains of the yeast Hanseniaspora uvarum contain cytoplasmic double-stranded RNAs (dsRNAs) of 4.7-kbp L and 1.0-kbp M species, which were shown to be separately packaged into icosahedral virus-like particles exhibiting RNA-dependent RNA polymerase activity. The L genome of the H. uvarum L-dsRNA virion HuV-L was shown to encode a 77-kDa major capsid protein. Peptide maps of the purified HuV coat protein and the 81-kDa major capsid protein from K1 killer viruses of Saccharomyces cerevisiae revealed distinctly different peptide patterns, suggesting significant sequence divergence at the level of the capsid-coding L-dsRNAs. In vitro transcripts from purified HuV-L particles showed no cross-hybridization to denatured L(A), L(B), or L(C), indicating that L from H. uvarum represents a unique L-dsRNA species. Weak, but clearly detectable cross-hybridization of the 1.0-kb dsRNA of HuV-M, encoding the secreted 18-kDa anti-Candida toxin, to the toxin-coding M genomes of S. cerevisiae K1, K2, and K28 killers indicated partial sequence homology among all of the M-dsRNAs tested.
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Affiliation(s)
- M J Schmitt
- Abteilung Angewandte Molekularbiologie, Institut für Mikrobiologie, Universität des Saarlandes, Saarbrücken, Germany.
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36
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Abstract
The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed.
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Affiliation(s)
- W Magliani
- Istituto di Microbiologia, Facoltà di Medicina e Chirurgia, Università degli Studi di Parma, Italy
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37
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38
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Chang H. Genetic engineering to enhance microbial interference and related therapeutic applications. Nat Biotechnol 1996; 14:444-7. [PMID: 9630918 DOI: 10.1038/nbt0496-444] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- H Chang
- US Food and Drug Administration, Rockville, MD 20857, USA.
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39
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Affiliation(s)
- R B Wickner
- Section on Genetics of Simple Eukaryotes, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892-0830, USA.
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40
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Vondrejs V, Janderová B, Valásek L. Yeast killer toxin K1 and its exploitation in genetic manipulations. Folia Microbiol (Praha) 1996; 41:379-93. [PMID: 9131795 DOI: 10.1007/bf02815687] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- V Vondrejs
- Department of Genetics and Microbiology, Faculty of Natural Science, Charles University, Prague, Czech Republic
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41
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Schmitt MJ, Compain P. Killer-toxin-resistant kre12 mutants of Saccharomyces cerevisiae: genetic and biochemical evidence for a secondary K1 membrane receptor. Arch Microbiol 1995; 164:435-43. [PMID: 8588746 DOI: 10.1007/bf02529742] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The Saccharomyces cerevisiae killer toxin K1 is a secreted alpha/beta-heterodimeric protein toxin that kills sensitive yeast cells in a receptor-mediated two-stage process. The first step involves toxin binding to beta-1,6-D-glucan-components of the outer yeast cell surface; this step is blocked in yeast mutants bearing nuclear mutations in any of the KRE genes whose products are involved in synthesis and/or assembly of cell wall beta-D-glucans. After binding to the yeast cell wall, the killer toxin is transferred to the cytoplasmic membrane, subsequently leading to cell death by forming lethal ion channels. In an attempt to identify a secondary K1 toxin receptor at the plasma membrane level, we mutagenized sensitive yeast strains and isolated killer-resistant (kre) mutants that were resistant as spheroplasts. Classical yeast genetics and successive back-crossings to sensitive wild-type strains indicated that this toxin resistance is due to mutation(s) in a single chromosomal yeast gene (KRE12), rendering kre12 mutants incapable of binding significant amounts of toxin to the membrane. Since kre12 mutants showed normal toxin binding to the cell wall, but markedly reduced membrane binding, we isolated and purified cytoplasmic membranes from a kre12 mutant and from an isogenic Kre12(+) strain and analyzed the membrane protein patterns by 2D-electrophoresis using a combination of isoelectric focusing and SDS-PAGE. Using this technique, three different proteins (or subunits of a single multimeric protein) were identified that were present in much lower amounts in the kre12 mutant. A model for K1 killer toxin action is presented in which the gene product of KRE12 functions in vivo as a K1 docking protein, facilitating toxin binding to the membrane and subsequent ion channel formation.
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Affiliation(s)
- M J Schmitt
- Institut für Mikrobiologie und Weinforschung, Johannes-Gutenberg-Universität Mainz, D-55099 Mainz, Germany
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42
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Schmitt MJ. Cloning and expression of a cDNA copy of the viral K28 killer toxin gene in yeast. MOLECULAR & GENERAL GENETICS : MGG 1995; 246:236-46. [PMID: 7862095 DOI: 10.1007/bf00294687] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The killer toxin K28, secreted by certain killer strains of the yeast Saccharomyces cerevisiae is genetically encoded by a 1.9 kb double-stranded RNA, M-dsRNA (M28), that is present within the cell as a cytoplasmically inherited virus-like particle (VLP). For stable maintenance and replication, M28-VLPs depend on a second dsRNA virus (LA), which has been shown to encode the major capsid protein (cap) and a capsid-polymerase fusion protein (cap-pol) that provides the toxin-coding M-satellites with their transcription and replicase functions. K28 toxin-coding M28-VLPs were isolated, purified and used in vitro for the synthesis of the single-stranded M28 transcript, which was shown to be of plus strand polarity and to bind to oligo(dT)-cellulose, indicating that M28(+)ssRNA contains an internal A-rich tract. Strand separation of the 1.9 kb M28-dsRNA and direct RNA sequencing of its 3' ends was performed in order to obtain specific DNA oligonucleotides that could be used as primers for cDNA synthesis. The nucleotide sequence of the toxin-coding M28-cDNA identified a single open reading frame (ORF) coding for a polypeptide of 345 amino acids, which contained two potential Kex2p/Kex1p processing sites and three potential sites for protein N-glycosylation. The toxin-coding cDNA was cloned and expressed in sensitive non-killer strains under the control of the yeast PGK promoter. Upon transformation, this construct conferred the complete K28 phenotype, demonstrating that both toxin and immunity determinants are contained within the cloned cDNA. In vitro translational analysis of the M28(+)ssRNA in vitro transcript identified the primary gene product of M28 as a K28 preprotoxin of 38 kDa (M-p38).
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Cloning, Molecular
- DNA, Complementary/genetics
- DNA-Directed RNA Polymerases/genetics
- DNA-Directed RNA Polymerases/metabolism
- Gene Expression
- Killer Factors, Yeast
- Molecular Sequence Data
- Mycotoxins/biosynthesis
- Mycotoxins/genetics
- Nucleic Acid Conformation
- Open Reading Frames
- Protein Biosynthesis
- Protein Precursors/genetics
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/isolation & purification
- RNA, Fungal/genetics
- RNA, Fungal/isolation & purification
- RNA, Viral/genetics
- RNA, Viral/isolation & purification
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/virology
- Saccharomyces cerevisiae Proteins
- Sequence Analysis, DNA
- Sequence Analysis, RNA
- Transcription, Genetic
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Affiliation(s)
- M J Schmitt
- Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg-Universität Mainz, Germany
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Chapter 7 Protein Glycosylation in Yeast. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60601-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2023]
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44
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Polashock JJ, Anagnostakis SL, Milgroom MG, Hillman BI. Isolation and characterization of a virus-resistant mutant of Cryphonectria parasitica. Curr Genet 1994; 26:528-34. [PMID: 7874748 DOI: 10.1007/bf00309945] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hypovirulent strain NB58 of Cryphonectria parasitica contains a dsRNA virus with a genome size of approximately 12.5 kb. Although NB58 is very stable in culture, a phenotypically-distinct sector arose which was found to be dsRNA-free. Attempts to infect the mutant strain, termed NB58F, by pairing with the parent strain (NB58) or other conversion-compatible, virus-containing strains have been unsuccessful. DNA fingerprint analysis showed that NB58, NB58F, and a representative dsRNA-free single-conidial isolate of NB58 termed NB58-19, were isogenic. The mutant culture was phenotypically stable, and all single-conidial progeny had the NB58F morphology. NB58F was intermediate between NB58 and NB58-19 in laccase production and virulence. Pigmentation and sporulation of NB58F, however, were reduced to near the level of NB58. In mating studies, NB58F functioned only as the male in sexual crosses. The mutant phenotype (F) predominated by a ratio of 5:2 among the ascospore progeny of F-type x wild-type crosses. These data suggest the lesion is nuclear and may be associated with a chromosomal abnormality. Attempts to infect the NB58F-type ascospore progeny failed, whereas the wild-type progeny were successfully infected with strains compatible with one or the other parent at a frequency of about 34%. Hyphal anastomosis and movement of cytoplasmic material occurred when NB58F was paired with a compatible strain, suggesting that the lesion is involved in viral maintenance as opposed to initial virus infection. NB58F represents the first virus-resistant isolate of C. parasitica to be described.
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Affiliation(s)
- J J Polashock
- Department of Plant Pathology, Rutgers University, New Brunswick, NJ 08903
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45
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Khoshnan A, Provenzano D, Alderete JF. Unique double-stranded RNAs associated with the Trichomonas vaginalis virus are synthesized by viral RNA-dependent RNA polymerase. J Virol 1994; 68:7108-14. [PMID: 7933092 PMCID: PMC237149 DOI: 10.1128/jvi.68.11.7108-7114.1994] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Most Trichomonas vaginalis isolates are carriers of the multisegmented double-stranded RNA (dsRNA) virus. In vitro polymerase assays were performed to demonstrate the RNA-dependent RNA polymerase (RDRP) activity of purified particles. Transcripts which comigrated with the dsRNAs of the virus were readily detected as synthesized products, indicating viral RDRP activity. In addition, smaller-sized dsRNA species, possibly two of approximately 700 bp (s1) and one of 500 bp (s2), were synthesized by purified virus particles of the CsCl gradient surrounding the virus peak. No cross-hybridization with either s1 or s2 and the dsRNA segments occurred, suggesting that s1 and s2 were synthesized from different templates. An RNase A protection assay revealed that the synthesized s1 and s2 polymerase products were double stranded. Furthermore, hybridization of products with strand-specific RNA of s1 generated from cDNA indicated that only one strand was synthesized in vitro. s1 and s2 were not visualized in ethidium bromide-stained agarose gels of dsRNA of infected trichomonads grown in batch cultures. However, dsRNA profiles of the same infected organisms cultivated under defined continuous-flow conditions contained readily detectable levels of s1 and s2, indicating that amplification of s1 and s2 occurred under specific environmental conditions. These newly discovered dsRNAs were not detected in all of the virus-carrying isolates. Finally, it is noteworthy that the s1 and s2 dsRNAs and the RDRP activity were not detected in trichomonal isolates without virus or in virus-negative progeny derived from virus-positive parental isolates. These data indicate the possibility of variations in the number of dsRNAs and/or of the presence of satellites in trichomonads infected with the multisegmented virus.
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Affiliation(s)
- A Khoshnan
- Department of Microbiology, University of Texas Health, Science Center, San Antonio 78284-7758
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46
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Schmitt MJ, Neuhausen F. Killer toxin-secreting double-stranded RNA mycoviruses in the yeasts Hanseniaspora uvarum and Zygosaccharomyces bailii. J Virol 1994; 68:1765-72. [PMID: 8107238 PMCID: PMC236637 DOI: 10.1128/jvi.68.3.1765-1772.1994] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Killer toxin-secreting strains of the yeasts Hanseniaspora uvarum and Zygosaccharomyces bailii were shown to contain linear double-stranded RNAs (dsRNAs) that persist within the cytoplasm of the infected host cell as encapsidated virus-like particles. In both yeasts, L- and M-dsRNAs were associated with 85-kDa major capsid protein, whereas the additional Z-dsRNA (2.8 kb), present only in the wild-type Z. bailii killer strain, was capsid protein, whereas the additional Z-dsRNA (2.8 kb), present only in the wild-type Z. bailii killer strain, was shown to be encapsidated by a 35-kDa coat protein. Although Northern (RNA) blot hybridizations indicated that L-dsRNA from Z. bailii is a LA species, additional peptide maps of the purified 85-kDa capsid from Z. bailii and the 88- and 80-kDa major coat proteins from K1 and K28 killer viruses of Saccharomyces cerevisiae revealed distinctly different patterns of peptides. Electron microscopy of purified Z. bailii viruses (ZbV) identified icosahedral particles 40 nm in diameter which were undistinguishable from the S. cerevisiae killer viruses. We demonstrated that purified ZbVs are sufficient to confer the Z. bailii killer phenotype on transfected spheroplasts of a S. cerevisiae nonkiller strain and that the resulting transfectants secreted even more killer toxin that the original ZbV donor strain did. Curing experiments with ZbV-transfected S. cerevisiae strains indicated that the M-dsRNA satellite from Z. bailii contains the genetic information for toxin production, whereas expression of toxin immunity might be dependent on Z-dsRNA, which resembles a new dsRNA replicon in yeasts that is not dependent on an LA helper virus to be stably maintained and replicated within the cell.
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Affiliation(s)
- M J Schmitt
- Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg-Universität Mainz, Germany
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47
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The primary and subunit structure of a novel type killer toxin produced by a halotolerant yeast, Pichia farinosa. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)42044-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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48
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Kurzweilov� H, Sigler K. Fluorescence staining of yeast cells permeabilized by killer toxin K1: Determination of optimum conditions. J Fluoresc 1993; 3:241-4. [DOI: 10.1007/bf00865270] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/1993] [Indexed: 10/26/2022]
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49
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Gooday GW. Cell envelope diversity and dynamics in yeasts and filamentous fungi. THE JOURNAL OF APPLIED BACTERIOLOGY 1993; 74 Suppl:12S-20S. [PMID: 8349531 DOI: 10.1111/j.1365-2672.1993.tb04338.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- G W Gooday
- Department of Molecular and Cell Biology, Marischal College, University of Aberdeen, UK
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50
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Weinstein LA, Capaldo-Kimball F, Leibowitz MJ. Genetics of heat-curability of killer virus of yeast. Yeast 1993; 9:411-8. [PMID: 7685559 DOI: 10.1002/yea.320090411] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The cytoplasmically inherited M double-stranded (ds) RNA genome segment of killer virus of Saccharomyces cerevisiae is heat-curable in some yeast strains but not in others. Temperature sensitivity is conferred on both M1 and M2 dsRNA satellite virus segments by the L-A-HN allele of the killer helper virus genome, but not by the L-A-H allele. Both diploidy and mating type heterozygosity of the host cell are also correlated with increased virus curability.
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Affiliation(s)
- L A Weinstein
- Department of Molecular Genetics and Microbiology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854-5635
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