1
|
Beckwith SL, Nomberg EJ, Newman AC, Taylor JV, Guerrero RC, Garfinkel DJ. An interchangeable prion-like domain is required for Ty1 retrotransposition. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.27.530227. [PMID: 36909481 PMCID: PMC10002725 DOI: 10.1101/2023.02.27.530227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
Retrotransposons and retroviruses shape genome evolution and can negatively impact genome function. Saccharomyces cerevisiae and its close relatives harbor several families of LTR-retrotransposons, the most abundant being Ty1 in several laboratory strains. The cytosolic foci that nucleate Ty1 virus-like particle (VLP) assembly are not well-understood. These foci, termed retrosomes or T-bodies, contain Ty1 Gag and likely Gag-Pol and the Ty1 mRNA destined for reverse transcription. Here, we report a novel intrinsically disordered N-terminal pr ion-like d omain (PrLD) within Gag that is required for transposition. This domain contains amino-acid composition similar to known yeast prions and is sufficient to nucleate prionogenesis in an established cell-based prion reporter system. Deleting the Ty1 PrLD results in dramatic VLP assembly and retrotransposition defects but does not affect Gag protein level. Ty1 Gag chimeras in which the PrLD is replaced with other sequences, including yeast and mammalian prionogenic domains, display a range of retrotransposition phenotypes from wildtype to null. We examine these chimeras throughout the Ty1 replication cycle and find that some support retrosome formation, VLP assembly, and retrotransposition, including the yeast Sup35 prion and the mouse PrP prion. Our interchangeable Ty1 system provides a useful, genetically tractable in vivo platform for studying PrLDs, complete with a suite of robust and sensitive assays, and host modulators developed to study Ty1 retromobility. Our work invites study into the prevalence of PrLDs in additional mobile elements. Significance Retrovirus-like retrotransposons help shape the genome evolution of their hosts and replicate within cytoplasmic particles. How their building blocks associate and assemble within the cell is poorly understood. Here, we report a novel pr ion-like d omain (PrLD) in the budding yeast retrotransposon Ty1 Gag protein that builds virus-like particles. The PrLD has similar sequence properties to prions and disordered protein domains that can drive the formation of assemblies that range from liquid to solid. We demonstrate that the Ty1 PrLD can function as a prion and that certain prion sequences can replace the PrLD and support Ty1 transposition. This interchangeable system is an effective platform to study additional disordered sequences in living cells.
Collapse
Affiliation(s)
- Sean L. Beckwith
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Emily J. Nomberg
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Abigail C. Newman
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Jeannette V. Taylor
- Robert P. Apkarian Integrated Electron Microscopy Core at Emory University, Atlanta, GA, 30322, USA
| | - Ricardo C. Guerrero
- Robert P. Apkarian Integrated Electron Microscopy Core at Emory University, Atlanta, GA, 30322, USA
| | - David J. Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| |
Collapse
|
2
|
Gazda LD, Joóné Matúz K, Nagy T, Mótyán JA, Tőzsér J. Biochemical characterization of Ty1 retrotransposon protease. PLoS One 2020; 15:e0227062. [PMID: 31917798 PMCID: PMC6952103 DOI: 10.1371/journal.pone.0227062] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 12/10/2019] [Indexed: 01/08/2023] Open
Abstract
Ty1 is one of the many transposons in the budding yeast Saccharomyces cerevisiae. The life-cycle of Ty1 shows numerous similarities with that of retroviruses, e.g. the initially synthesized polyprotein precursor undergoes proteolytic processing by the protease. The retroviral proteases have become important targets of current antiretroviral therapies due to the critical role of the limited proteolysis of Gag-Pol polyprotein in the replication cycle and they therefore belong to the most well-studied enzymes. Comparative analyses of retroviral and retroviral-like proteases can help to explore the key similarities and differences which may help understanding how resistance is developed against protease inhibitors, but the available information about the structural and biochemical characteristics of retroviral-like, and especially retrotransposon, proteases is limited. To investigate the main characteristics of Ty1 retrotransposon protease of Saccharomyces cerevisiae, untagged and His6-tagged forms of Ty1 protease were expressed in E. coli. After purification of the recombinant proteins, activity measurements were performed using synthetic oligopeptide and fluorescent recombinant protein substrates, which represented the wild-type and the modified forms of naturally occurring cleavage sites of the protease. We investigated the dependence of enzyme activity on different reaction conditions (pH, temperature, ionic strength, and urea concentration), and determined enzyme kinetic parameters for the studied substrates. Inhibitory potentials of 10 different protease inhibitors were also tested. Ty1 protease was not inhibited by the inhibitors which have been designed against human immunodeficiency virus type 1 protease and are approved as antiretroviral therapeutics. A quaternary structure of homodimeric Ty1 protease was proposed based on homology modeling, and this structure was used to support interpretation of experimental results and to correlate some structural and biochemical characteristics with that of other retroviral proteases.
Collapse
Affiliation(s)
- Lívia Diána Gazda
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Krisztina Joóné Matúz
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tibor Nagy
- Department of Applied Chemistry, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - János András Mótyán
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- * E-mail: (JAM); (JT)
| | - József Tőzsér
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- * E-mail: (JAM); (JT)
| |
Collapse
|
3
|
Rowley PA. The frenemies within: viruses, retrotransposons and plasmids that naturally infect Saccharomyces yeasts. Yeast 2017; 34:279-292. [PMID: 28387035 DOI: 10.1002/yea.3234] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/28/2017] [Accepted: 03/29/2017] [Indexed: 11/07/2022] Open
Abstract
Viruses are a major focus of current research efforts because of their detrimental impact on humanity and their ubiquity within the environment. Bacteriophages have long been used to study host-virus interactions within microbes, but it is often forgotten that the single-celled eukaryote Saccharomyces cerevisiae and related species are infected with double-stranded RNA viruses, single-stranded RNA viruses, LTR-retrotransposons and double-stranded DNA plasmids. These intracellular nucleic acid elements have some similarities to higher eukaryotic viruses, i.e. yeast retrotransposons have an analogous lifecycle to retroviruses, the particle structure of yeast totiviruses resembles the capsid of reoviruses and segregation of yeast plasmids is analogous to segregation strategies used by viral episomes. The powerful experimental tools available to study the genetics, cell biology and evolution of S. cerevisiae are well suited to further our understanding of how cellular processes are hijacked by eukaryotic viruses, retrotransposons and plasmids. This article has been written to briefly introduce viruses, retrotransposons and plasmids that infect Saccharomyces yeasts, emphasize some important cellular proteins and machineries with which they interact, and suggest the evolutionary consequences of these interactions. Copyright © 2017 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- Paul A Rowley
- Department of Biological Sciences, The University of Idaho, Moscow, Idaho, USA
| |
Collapse
|
4
|
Determinants of Genomic RNA Encapsidation in the Saccharomyces cerevisiae Long Terminal Repeat Retrotransposons Ty1 and Ty3. Viruses 2016; 8:v8070193. [PMID: 27428991 PMCID: PMC4974528 DOI: 10.3390/v8070193] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 06/21/2016] [Accepted: 06/28/2016] [Indexed: 12/12/2022] Open
Abstract
Long-terminal repeat (LTR) retrotransposons are transposable genetic elements that replicate intracellularly, and can be considered progenitors of retroviruses. Ty1 and Ty3 are the most extensively characterized LTR retrotransposons whose RNA genomes provide the template for both protein translation and genomic RNA that is packaged into virus-like particles (VLPs) and reverse transcribed. Genomic RNAs are not divided into separate pools of translated and packaged RNAs, therefore their trafficking and packaging into VLPs requires an equilibrium between competing events. In this review, we focus on Ty1 and Ty3 genomic RNA trafficking and packaging as essential steps of retrotransposon propagation. We summarize the existing knowledge on genomic RNA sequences and structures essential to these processes, the role of Gag proteins in repression of genomic RNA translation, delivery to VLP assembly sites, and encapsidation.
Collapse
|
5
|
Garfinkel DJ, Tucker JM, Saha A, Nishida Y, Pachulska-Wieczorek K, Błaszczyk L, Purzycka KJ. A self-encoded capsid derivative restricts Ty1 retrotransposition in Saccharomyces. Curr Genet 2015; 62:321-9. [PMID: 26650614 DOI: 10.1007/s00294-015-0550-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 11/24/2015] [Indexed: 11/27/2022]
Abstract
Retrotransposons and retroviral insertions have molded the genomes of many eukaryotes. Since retroelements transpose via an RNA intermediate, the additive nature of the replication cycle can result in massive increases in copy number if left unchecked. Host organisms have countered with several defense systems, including domestication of retroelement genes that now act as restriction factors to minimize propagation. We discovered a novel truncated form of the Saccharomyces Ty1 retrotransposon capsid protein, dubbed p22 that inhibits virus-like particle (VLP) assembly and function. The p22 restriction factor expands the repertoire of defense proteins targeting the capsid and highlights a novel host-parasite strategy. Instead of inhibiting all transposition by domesticating the restriction gene as a distinct locus, Ty1 and budding yeast may have coevolved a relationship that allows high levels of transposition when Ty1 copy numbers are low and progressively less transposition as copy numbers rise. Here, we offer a perspective on p22 restriction, including its mode of expression, effect on VLP functions, interactions with its target, properties as a nucleic acid chaperone, similarities to other restriction factors, and future directions.
Collapse
Affiliation(s)
- David J Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, USA.
| | - Jessica M Tucker
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, USA
| | - Agniva Saha
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, USA
| | - Yuri Nishida
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, USA
| | - Katarzyna Pachulska-Wieczorek
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Leszek Błaszczyk
- Institute of Computing Science, Poznan University of Technology, Poznan, Poland
| | - Katarzyna J Purzycka
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| |
Collapse
|
6
|
Suresh S, Ahn HW, Joshi K, Dakshinamurthy A, Kananganat A, Garfinkel DJ, Farabaugh PJ. Ribosomal protein and biogenesis factors affect multiple steps during movement of the Saccharomyces cerevisiae Ty1 retrotransposon. Mob DNA 2015; 6:22. [PMID: 26664557 PMCID: PMC4673737 DOI: 10.1186/s13100-015-0053-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 11/30/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND A large number of Saccharomyces cerevisiae cellular factors modulate the movement of the retrovirus-like transposon Ty1. Surprisingly, a significant number of chromosomal genes required for Ty1 transposition encode components of the translational machinery, including ribosomal proteins, ribosomal biogenesis factors, protein trafficking proteins and protein or RNA modification enzymes. RESULTS To assess the mechanistic connection between Ty1 mobility and the translation machinery, we have determined the effect of these mutations on ribosome biogenesis and Ty1 transcriptional and post-transcriptional regulation. Lack of genes encoding ribosomal proteins or ribosome assembly factors causes reduced accumulation of the ribosomal subunit with which they are associated. In addition, these mutations cause decreased Ty1 + 1 programmed translational frameshifting, and reduced Gag protein accumulation despite at least normal levels of Ty1 mRNA. Several ribosome subunit mutations increase the level of both an internally initiated Ty1 transcript and its encoded truncated Gag-p22 protein, which inhibits transposition. CONCLUSIONS Together, our results suggest that this large class of cellular genes modulate Ty1 transposition through multiple pathways. The effects are largely post-transcriptional acting at a variety of levels that may include translation initiation, protein stability and subcellular protein localization.
Collapse
Affiliation(s)
- Susmitha Suresh
- />Department of Biological Sciences and Program in Molecular and Cell Biology, University of Maryland Baltimore County, Baltimore, MD 21250 USA
- />Present address: Division of Infectious Diseases, Department of Internal Medicine, Stanford University School of Medicine, Stanford, California 94305 USA
| | - Hyo Won Ahn
- />Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA 30602 USA
| | - Kartikeya Joshi
- />Department of Biological Sciences and Program in Molecular and Cell Biology, University of Maryland Baltimore County, Baltimore, MD 21250 USA
| | - Arun Dakshinamurthy
- />Department of Biological Sciences and Program in Molecular and Cell Biology, University of Maryland Baltimore County, Baltimore, MD 21250 USA
- />Present address: Department of Nanosciences and Technology, Karunya University, Karunya Nagar, Coimbatore, 641 114 Tamil Nadu India
| | - Arun Kananganat
- />Department of Biological Sciences and Program in Molecular and Cell Biology, University of Maryland Baltimore County, Baltimore, MD 21250 USA
| | - David J. Garfinkel
- />Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA 30602 USA
| | - Philip J. Farabaugh
- />Department of Biological Sciences and Program in Molecular and Cell Biology, University of Maryland Baltimore County, Baltimore, MD 21250 USA
| |
Collapse
|
7
|
Nishida Y, Pachulska-Wieczorek K, Błaszczyk L, Saha A, Gumna J, Garfinkel DJ, Purzycka KJ. Ty1 retrovirus-like element Gag contains overlapping restriction factor and nucleic acid chaperone functions. Nucleic Acids Res 2015; 43:7414-31. [PMID: 26160887 PMCID: PMC4551931 DOI: 10.1093/nar/gkv695] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 06/26/2015] [Indexed: 12/13/2022] Open
Abstract
Ty1 Gag comprises the capsid of virus-like particles and provides nucleic acid chaperone (NAC) functions during retrotransposition in budding yeast. A subgenomic Ty1 mRNA encodes a truncated Gag protein (p22) that is cleaved by Ty1 protease to form p18. p22/p18 strongly inhibits transposition and can be considered an element-encoded restriction factor. Here, we show that only p22 and its short derivatives restrict Ty1 mobility whereas other regions of GAG inhibit mobility weakly if at all. Mutational analyses suggest that p22/p18 is synthesized from either of two closely spaced AUG codons. Interestingly, AUG1p18 and AUG2p18 proteins display different properties, even though both contain a region crucial for RNA binding and NAC activity. AUG1p18 shows highly reduced NAC activity but specific binding to Ty1 RNA, whereas AUG2p18 shows the converse behavior. p22/p18 affects RNA encapsidation and a mutant derivative defective for RNA binding inhibits the RNA chaperone activity of the C-terminal region (CTR) of Gag-p45. Moreover, affinity pulldowns show that p18 and the CTR interact. These results support the idea that one aspect of Ty1 restriction involves inhibition of Gag-p45 NAC functions by p22/p18-Gag interactions.
Collapse
Affiliation(s)
- Yuri Nishida
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Katarzyna Pachulska-Wieczorek
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
| | - Leszek Błaszczyk
- Institute of Computing Science, Poznan University of Technology, 60-965 Poznan, Poland
| | - Agniva Saha
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Julita Gumna
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
| | - David J Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Katarzyna J Purzycka
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
| |
Collapse
|
8
|
Saha A, Mitchell JA, Nishida Y, Hildreth JE, Ariberre JA, Gilbert WV, Garfinkel DJ. A trans-dominant form of Gag restricts Ty1 retrotransposition and mediates copy number control. J Virol 2015; 89:3922-38. [PMID: 25609815 PMCID: PMC4403431 DOI: 10.1128/jvi.03060-14] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 01/15/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Saccharomyces cerevisiae and Saccharomyces paradoxus lack the conserved RNA interference pathway and utilize a novel form of copy number control (CNC) to inhibit Ty1 retrotransposition. Although noncoding transcripts have been implicated in CNC, here we present evidence that a truncated form of the Gag capsid protein (p22) or its processed form (p18) is necessary and sufficient for CNC and likely encoded by Ty1 internal transcripts. Coexpression of p22/p18 and Ty1 decreases mobility more than 30,000-fold. p22/p18 cofractionates with Ty1 virus-like particles (VLPs) and affects VLP yield, protein composition, and morphology. Although p22/p18 and Gag colocalize in the cytoplasm, p22/p18 disrupts sites used for VLP assembly. Glutathione S-transferase (GST) affinity pulldowns also suggest that p18 and Gag interact. Therefore, this intrinsic Gag-like restriction factor confers CNC by interfering with VLP assembly and function and expands the strategies used to limit retroelement propagation. IMPORTANCE Retrotransposons dominate the chromosomal landscape in many eukaryotes, can cause mutations by insertion or genome rearrangement, and are evolutionarily related to retroviruses such as HIV. Thus, understanding factors that limit transposition and retroviral replication is fundamentally important. The present work describes a retrotransposon-encoded restriction protein derived from the capsid gene of the yeast Ty1 element that disrupts virus-like particle assembly in a dose-dependent manner. This form of copy number control acts as a molecular rheostat, allowing high levels of retrotransposition when few Ty1 elements are present and inhibiting transposition as copy number increases. Thus, yeast and Ty1 have coevolved a form of copy number control that is beneficial to both "host and parasite." To our knowledge, this is the first Gag-like retrotransposon restriction factor described in the literature and expands the ways in which restriction proteins modulate retroelement replication.
Collapse
Affiliation(s)
- Agniva Saha
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Jessica A Mitchell
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Yuri Nishida
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Jonathan E Hildreth
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Joshua A Ariberre
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Wendy V Gilbert
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - David J Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| |
Collapse
|
9
|
Lim SL, Kortschak RD, Adelson DL. Discovery of a novel long terminal repeat (LTR2i_SS) in Sus Scrofa. Anim Genet 2014; 45:367-72. [DOI: 10.1111/age.12138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Sim L. Lim
- School of Molecular and Biomedical Science; The University of Adelaide; North Terrace, Adelaide 5005 SA Australia
| | - R. Daniel Kortschak
- School of Molecular and Biomedical Science; The University of Adelaide; North Terrace, Adelaide 5005 SA Australia
| | - David L. Adelson
- School of Molecular and Biomedical Science; The University of Adelaide; North Terrace, Adelaide 5005 SA Australia
| |
Collapse
|
10
|
Tomita M. Revolver and superior: novel transposon-like gene families of the plant kingdom. Curr Genomics 2011; 11:62-9. [PMID: 20808526 PMCID: PMC2851119 DOI: 10.2174/138920210790217954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 10/29/2009] [Accepted: 10/29/2009] [Indexed: 11/22/2022] Open
Abstract
High-throughput sequencing of eukaryotic genomes has revived interest in the structure and function of repetitive genomic sequences, previously referred to as junk DNA. Repetitive sequences, including transposable elements, are now believed to play a significant role in genomic differentiation and evolution. Some are also expressed as regulatory noncoding RNAs. Vast DNA databases exist for higher eukaryotes; however, with the exception of homologues of known repetitive-sequence-families and transposable elements, most repetitive elements still need to be annotated. Revolver and Superior, both discovered in the Triticeae, are novel classes of transposon-like genes and major components of large cereal genomes. Revolver was isolated from rye via genome subtraction of sequences common to rye and wheat. Superior was isolated from rye by cleavage with EcoO109I, the recognition sites of which consist of a 5'- PuGGNCCPy-3' multi-sequence. Revolver is 2929-3041 bp long with an inverted repeat sequence on each end. The Superior family elements are 1292-1432 bp in length, with divergent 5' regions, indicating the presence of considerable structural diversity. Revolver and Superior are transcriptionally active elements; Revolver harbors a single gene consisting of three exons and two introns, encoding a protein of 139 amino acid residues. Revolver variants range in size from 2665 bp to 4269 bp, with some variants lacking the 5' region, indicating structural diversity around the first exon. Revolver and Superior are dispersed across all seven chromosomes of rye. Revolver has existed since the diploid progenitor of wheat, and has been amplified or lost in several species during the evolution of the Triticeae. This article reviews the recently discovered Revolver and Superior families of plant transposons, which do not share identity with any known autonomous transposable elements or repetitive elements from any living species.
Collapse
Affiliation(s)
- Motonori Tomita
- Molecular Genetics Laboratory, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan
| |
Collapse
|
11
|
Li J, Zhao GH, Li XY, Chen F, Chen JB, Zou FC, Yang JF, Lin RQ, Weng YB, Zhu XQ. IRAP: An efficient retrotransposon-based electrophoretic technique for studying genetic variability among geographical isolates of Schistosoma japonicum. Electrophoresis 2011; 32:1473-9. [PMID: 21626522 DOI: 10.1002/elps.201100044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 03/04/2011] [Accepted: 03/04/2011] [Indexed: 11/12/2022]
Abstract
In the present study, a inter-retrotransposon-amplified polymorphism (IRAP) technique, based on retrotransposons, was used to examine genetic variability among Schistosoma japonicum isolates from different provinces in mainland China. Of the 15 primers screened, 5 produced highly reproducible IRAP patterns. Using these primers, 54 discernible DNA fragments were generated with 40 (74.07%) being polymorphic, indicating considerable genetic variation among the examined S. japonicum isolates. The primer LTR-11 was found to be able to differentiate male and female parasites, producing one constant specific band for female S. japonicum isolates. The percentages of polymorphic bands (PPB) among all parasites, among isolates from mountainous provinces and among those from the lake/marshland areas were 74.07, 48.15, and 66.67%, respectively. UPGMA analysis revealed that the IRAP profiles could group S. japonicum isolates in mainland China into two clades (mountainous and lake/marshland types), and samples from the same geographical origins clustered together. These results demonstrated that the IRAP technique is suitable for studying genetic diversity and population structures, and also provides an effective technique for studying sex differentiation of S. japonicum.
Collapse
Affiliation(s)
- Juan Li
- State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, CAAS, Lanzhou, Gansu Province, P R China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Malagon F, Jensen TH. T-body formation precedes virus-like particle maturation in S. cerevisiae. RNA Biol 2011; 8:184-9. [PMID: 21358276 DOI: 10.4161/rna.8.2.14822] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
T-bodies are localized S. cerevisiae RNPs containing Ty1 retroviral components and speculated to play a role in the assembly of virus-like particles (VLPs). Mapping requirements for T-body formation, we demonstrate that ectopic expression of immature TyA1/Gag (Gag-p49), a structural component of the Ty1 capsid, is sufficient for T-body formation both under normal conditions as well as in a strain background devoid of endogenous Gag. Moreover, T-bodies are readily formed when Ty1 transposition is blocked. Thus, T-bodies represent an early stage in the Ty1 life cycle, preceding VLP maturation.
Collapse
Affiliation(s)
- Francisco Malagon
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, Aarhus University, Aarhus C., Denmark. or
| | | |
Collapse
|
13
|
BUD22 affects Ty1 retrotransposition and ribosome biogenesis in Saccharomyces cerevisiae. Genetics 2010; 185:1193-205. [PMID: 20498295 DOI: 10.1534/genetics.110.119115] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A variety of cellular factors affect the movement of the retrovirus-like transposon Ty1. To identify genes involved in Ty1 virus-like particle (VLP) function, the level of the major capsid protein (Gag-p45) and its proteolytic precursor (Gag-p49p) was monitored in a subset of Ty1 cofactor mutants. Twenty-nine of 87 mutants contained alterations in the level of Gag; however, only bud22Delta showed a striking defect in Gag processing. BUD22 affected the +1 translational frameshifting event required to express the Pol proteins protease, integrase, and reverse transcriptase. Therefore, it is possible that the bud22Delta mutant may not produce enough functional Ty1 protease to completely process Gag-p49 to p45. Furthermore, BUD22 is required for 18S rRNA processing and 40S subunit biogenesis and influences polysome density. Together our results suggest that BUD22 is involved in a step in ribosome biogenesis that not only affects general translation, but also may alter the frameshifting efficiency of ribosomes, an event central to Ty1 retrotransposition.
Collapse
|
14
|
Checkley MA, Nagashima K, Lockett SJ, Nyswaner KM, Garfinkel DJ. P-body components are required for Ty1 retrotransposition during assembly of retrotransposition-competent virus-like particles. Mol Cell Biol 2010; 30:382-98. [PMID: 19901074 PMCID: PMC2798465 DOI: 10.1128/mcb.00251-09] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 04/20/2009] [Accepted: 10/29/2009] [Indexed: 01/24/2023] Open
Abstract
Ty1 is a retrovirus-like retrotransposon whose replication is influenced by diverse cellular processes in Saccharomyces cerevisiae. We have identified cytoplasmic P-body components encoded by DHH1, KEM1, LSM1, and PAT1 as cofactors that posttranscriptionally enhance Ty1 retrotransposition. Using fluorescent in situ hybridization and immunofluorescence microscopy, we found that Ty1 mRNA and Gag colocalize to discrete cytoplasmic foci in wild-type cells. These foci, which are distinct from P-bodies, do not form in P-body component mutants or under conditions suboptimal for retrotransposition. Our immunoelectron microscopy (IEM) data suggest that mRNA/Gag foci are sites where virus-like particles (VLPs) cluster. Overexpression of Ty1 leads to a large increase in retrotransposition in wild-type cells, which allows VLPs to be detected by IEM. However, retrotransposition is still reduced in P-body component mutants under these conditions. Moreover, the percentage of Ty1 mRNA/Gag foci and VLP clusters and levels of integrase and reverse transcriptase are reduced in these mutants. Ty1 antisense RNAs, which have been reported to inhibit Ty1 transposition, are more abundant in the kem1Delta mutant and colocalize with Ty1 mRNA in the cytoplasm. Therefore, Kem1p may prevent the aggregation of Ty1 antisense and mRNAs. Overall, our results suggest that P-body components enhance the formation of retrotransposition-competent Ty1 VLPs.
Collapse
Affiliation(s)
- Mary Ann Checkley
- Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research National Cancer Institute, Frederick, Maryland 21702-1201, Advanced Technology Program, SAIC—Frederick, Inc., NCI—Frederick, Frederick, Maryland 21702-1201
| | - Kunio Nagashima
- Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research National Cancer Institute, Frederick, Maryland 21702-1201, Advanced Technology Program, SAIC—Frederick, Inc., NCI—Frederick, Frederick, Maryland 21702-1201
| | - Stephen J. Lockett
- Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research National Cancer Institute, Frederick, Maryland 21702-1201, Advanced Technology Program, SAIC—Frederick, Inc., NCI—Frederick, Frederick, Maryland 21702-1201
| | - Katherine M. Nyswaner
- Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research National Cancer Institute, Frederick, Maryland 21702-1201, Advanced Technology Program, SAIC—Frederick, Inc., NCI—Frederick, Frederick, Maryland 21702-1201
| | - David J. Garfinkel
- Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research National Cancer Institute, Frederick, Maryland 21702-1201, Advanced Technology Program, SAIC—Frederick, Inc., NCI—Frederick, Frederick, Maryland 21702-1201
| |
Collapse
|
15
|
Abstract
The Ty1 retrotransposon of Saccharomyces cerevisiae is comprised of structural and enzymatic proteins that are functionally similar to those of retroviruses. Despite overall sequence divergence, certain motifs are highly conserved. We have examined the Ty1 integrase (IN) zinc binding domain by mutating the definitive histidine and cysteine residues and thirteen residues in the intervening (X(32)) sequence between IN-H22 and IN-C55. Mutation of the zinc-coordinating histidine or cysteine residues reduced transposition by more than 4,000-fold and led to IN and reverse transcriptase (RT) instability as well as inefficient proteolytic processing. Alanine substitution of the hydrophobic residues I28, L32, I37 and V45 in the X(32) region reduced transposition 85- to 688-fold. Three of these residues, L32, I37, and V45, are highly conserved among retroviruses, although their effects on integration or viral infectivity have not been characterized. In contrast to the HHCC mutants, all the X(32) mutants exhibited stable IN and RT, and protein processing and cDNA production were unaffected. However, glutathione S-transferase pulldowns and intragenic complementation analysis of selected transposition-defective X(32) mutants revealed decreased IN-IN interactions. Furthermore, virus-like particles with in-L32A and in-V45A mutations did not exhibit substantial levels of concerted integration products in vitro. Our results suggest that the histidine/cysteine residues are important for steps in transposition prior to integration, while the hydrophobic residues function in IN multimerization.
Collapse
|
16
|
Tomita M, Shinohara K, Morimoto M. Revolver is a new class of transposon-like gene composing the triticeae genome. DNA Res 2008; 15:49-62. [PMID: 18303044 PMCID: PMC2650628 DOI: 10.1093/dnares/dsm029] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Revolver discovered in the Triticeae plant is a novel class of transposon-like gene and a major component of the large cereal genome. An 89 bp segment of Revolver that is enriched in the genome of rye was isolated by deleting the DNA sequences common to rye and wheat. The entire structure of Revolver was determined by using rye genomic clones, which were screened by the 89 bp probe. Revolver consists of 2929-3041 bp with an inverted repeated sequence on each end and is dispersed through all seven chromosomes of the rye genome. Revolver is transcriptionally active, and the isolated full-length cDNA (726 bp) reveals that Revolver harbors a single gene consisting of three exons (342, 88, and 296 bp) and two introns (750 and 1237 bp), and encodes 139 amino acid residues of protein, which shows similarity to some transcriptional regulators. Revolver variants ranging from 2665 to 4269 bp, in which 5' regions were destructed, indicate structural diversities around the first exon. Revolver does not share identity with any known class I or class II autonomous transposable elements of any living species. DNA blot analysis of Triticeae plants shows that Revolver has existed since the diploid progenitor of wheat, and has been amplified or lost in several species during the evolution of the Triticeae.
Collapse
Affiliation(s)
- Motonori Tomita
- Molecular Genetics Laboratory, Faculty of Agriculture, Tottori University, 101, Koyama-minami 4-chome, Tottori City, Tottori 680-8553, Japan.
| | | | | |
Collapse
|
17
|
Forbes EM, Nieduszynska SR, Brunton FK, Gibson J, Glover LA, Stansfield I. Control of gag-pol gene expression in the Candida albicans retrotransposon Tca2. BMC Mol Biol 2007; 8:94. [PMID: 17961216 PMCID: PMC2194720 DOI: 10.1186/1471-2199-8-94] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Accepted: 10/25/2007] [Indexed: 11/10/2022] Open
Abstract
Background In the C. albicans retrotransposon Tca2, the gag and pol ORFs are separated by a UGA stop codon, 3' of which is a potential RNA pseudoknot. It is unclear how the Tca2 gag UGA codon is bypassed to allow pol expression. However, in other retroelements, translational readthrough of the gag stop codon can be directed by its flanking sequence, including a 3' pseudoknot. Results The hypothesis was tested that in Tca2, gag stop codon flanking sequences direct translational readthrough and synthesis of a gag-pol fusion protein. Sequence from the Tca2 gag-UGA-pol junction (300 nt) was inserted between fused lacZ and luciferase (luc) genes in a Saccharomyces cerevisiae dual reporter construct. Although downstream of UGA, luc was expressed, but its expression was unaffected by inserting additional stop codons at the 3' end of lacZ. Luc expression was instead being driven by a previously unknown minor promoter activity within the gag-pol junction region. Evidence together indicated that junction sequence alone cannot direct UGA readthrough. Using reporter genes in C. albicans, the activities of this gag-pol junction promoter and the Tca2 long terminal repeat (LTR) promoter were compared. Of the two promoters, only the LTR promoter was induced by heat-shock, which also triggers retrotransposition. Tca2 pol protein, epitope-tagged in C. albicans to allow detection, was also heat-shock induced, indicating that pol proteins were expressed from a gag-UGA-pol RNA. Conclusion This is the first demonstration that the LTR promoter directs Tca2 pol protein expression, and that pol proteins are translated from a gag-pol RNA, which thus requires a mechanism for stop codon bypass. However, in contrast to most other retroelement and viral readthrough signals, immediate gag UGA-flanking sequences were insufficient to direct stop readthrough in S. cerevisiae, indicating non-canonical mechanisms direct gag UGA bypass in Tca2.
Collapse
Affiliation(s)
- Elaine M Forbes
- University of Aberdeen, School of Medical Sciences, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK.
| | | | | | | | | | | |
Collapse
|
18
|
Abstract
The development of more advanced and effective vaccines is of great interest in modern medicine. These new-generation vaccines, based on recombinant proteins or DNA, are often less reactogenic and immunogenic than traditional vaccines. Thus, there is an urgent need for the development of new and improved adjuvants. Besides many other immunostimulatory components, the bacterial ghost (BG) system is currently under investigation as a potent vaccine delivery system with intrinsic adjuvant properties. BGs are nonliving cell envelope preparations from Gram-negative cells, devoid of cytoplasmic contents, while their cellular morphology and native surface antigenic structures remain preserved. Owing to the particulate nature of BGs and the fact that they contain many well known immune-stimulating compounds, BGs have the potential to enhance immune responses against ghost-delivered target antigens.
Collapse
MESH Headings
- Adjuvants, Immunologic/administration & dosage
- Animals
- Antigens, Bacterial/administration & dosage
- Antigens, Bacterial/genetics
- Antigens, Bacterial/immunology
- Chemistry, Pharmaceutical
- Drug Carriers
- Genetic Vectors
- Gram-Negative Bacteria/genetics
- Gram-Negative Bacteria/immunology
- Humans
- Immunity, Mucosal
- Technology, Pharmaceutical/trends
- Vaccines, DNA/administration & dosage
- Vaccines, DNA/genetics
- Vaccines, DNA/immunology
- Vaccines, Subunit/administration & dosage
- Vaccines, Subunit/genetics
- Vaccines, Subunit/immunology
Collapse
Affiliation(s)
- Eva M Riedmann
- Department of Chromosome Biology, Max F Perutz Laboratories, University of Vienna, Vienna, Austria.
| | | | | | | |
Collapse
|
19
|
Wilhelm M, Wilhelm FX. Cooperation between reverse transcriptase and integrase during reverse transcription and formation of the preintegrative complex of Ty1. EUKARYOTIC CELL 2006; 5:1760-9. [PMID: 17031000 PMCID: PMC1595340 DOI: 10.1128/ec.00159-06] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Reverse transcriptase (RT) and integrase (IN) play a central role in the replication and transposition of retroelements. Increasing evidence suggests that the interaction between these two enzymes is functional and plays an important role in replication. In the yeast Saccharomyces cerevisiae retrotransposon Ty1, the interaction of IN with RT is critical for the formation of an active conformation of RT. We show here that the RT associated with VLPs is active only if it is in close interaction with IN. To probe the IN-RT cis-trans relationship, we have used a complementation assay based on coexpressing two transposons. We show that IN acts in cis to activate RT and that a functional integrase provided in trans is not able to complement replication and transposition defects of IN deletion or IN active-site mutant elements. Our data support a model in which IN not only interacts closely with RT during reverse transcription but also remains associated with RT during the formation of the preintegrative complex.
Collapse
Affiliation(s)
- Marcelle Wilhelm
- Institut de Biologie Moleculaire et Cellulaire, 15 Rue R. Descartes, 67084 Strasbourg, France.
| | | |
Collapse
|
20
|
Wilhelm FX, Wilhelm M, Gabriel A. Reverse transcriptase and integrase of the Saccharomyces cerevisiae Ty1 element. Cytogenet Genome Res 2005; 110:269-87. [PMID: 16093680 DOI: 10.1159/000084960] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Accepted: 02/02/2004] [Indexed: 11/19/2022] Open
Abstract
Integrase (IN) and reverse transcriptase (RT) play a central role in transposition of retroelements. The mechanism of integration by IN and the steps of the replication process mediated by RT are briefly described here. Recently, active recombinant forms of Ty1 IN and RT have been obtained. This has allowed a more detailed understanding of their biochemical and structural properties and has made possible combined in vitro and in vivo analyses of their functions. A focus of this review is to discuss some of the results obtained thus far with these two recombinant proteins and to propose future directions.
Collapse
Affiliation(s)
- F-X Wilhelm
- Institut de Biologie Moleculaire et Cellulaire, Strasbourg, France.
| | | | | |
Collapse
|
21
|
Wilhelm M, Wilhelm FX. Role of integrase in reverse transcription of the Saccharomyces cerevisiae retrotransposon Ty1. EUKARYOTIC CELL 2005; 4:1057-65. [PMID: 15947198 PMCID: PMC1151998 DOI: 10.1128/ec.4.6.1057-1065.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Reverse transcriptase (RT) with its associated RNase H (RH) domain and integrase (IN) are key enzymes encoded by retroviruses and retrotransposons. Several studies have implied a functional role of the interaction between IN and RT during the replication of retroviral and retrotransposon genomes. In this study, IN deletion mutants were used to investigate the role of IN on the RT activity of the yeast Saccharomyces cerevisiae retrotransposon Ty1. We have identified two domains of Ty1 integrase which have effects on RT activity in vivo. The deletion of a domain spanning amino acid residues 233 to 520 of IN increases the exogenous specific activity of RT up to 20-fold, whereas the removal of a region rich in acidic amino acid residues between residues 521 and 607 decreases its activity. The last result complements our observation that an active recombinant RT protein can be obtained if a small acidic tail mimicking the acidic domain of IN is fused to the RT-RH domain. We suggest that interaction between these acidic amino acid residues of IN and a basic region of RT could be critical for the correct folding of RT and for the formation of an active conformation of the enzyme.
Collapse
Affiliation(s)
- M Wilhelm
- Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg, France.
| | | |
Collapse
|
22
|
Jechlinger W, Haller C, Resch S, Hofmann A, Szostak MP, Lubitz W. Comparative immunogenicity of the hepatitis B virus core 149 antigen displayed on the inner and outer membrane of bacterial ghosts. Vaccine 2005; 23:3609-17. [PMID: 15855021 DOI: 10.1016/j.vaccine.2004.11.078] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Accepted: 11/17/2004] [Indexed: 11/17/2022]
Abstract
Two membrane compartments of Escherichia coli ghosts, representing empty bacterial cell envelopes, were investigated as carriers of foreign antigens. By subcutaneous immunisation of mice the immunogenicity of bacterial ghosts carrying the Hepatitis B virus core 149 protein (HBcAg-149) as model antigen anchored either in the inner or the outer membrane of E. coli was compared. Both systems induced significant immune responses against the foreign target antigen, the HBcAg-149, in mice. Results indicate that bacterial ghosts provide an excellent carrier system for antigen delivery.
Collapse
Affiliation(s)
- Wolfgang Jechlinger
- Institute of Microbiology and Genetics, Section Microbiology and Biotechnology, University of Vienna, UZA II, 2B522, Althanstrasse 14, A-1090 Wien, Austria.
| | | | | | | | | | | |
Collapse
|
23
|
Egan MA. Current prospects for the development of a therapeutic vaccine for the treatment of HIV type 1 infection. AIDS Res Hum Retroviruses 2004; 20:794-806. [PMID: 15320982 DOI: 10.1089/0889222041725244] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Michael A Egan
- Department of Immunobiology, Wyeth Vaccines Research, Pearl River, New York, 10965, USA.
| |
Collapse
|
24
|
Slibinskas R, Zvirbliene A, Gedvilaite A, Samuel D, Jin L, Beard S, Staniulis J, Sasnauskas K. Synthesis of mumps virus nucleocapsid protein in yeast Pichia pastoris. J Biotechnol 2003; 103:43-9. [PMID: 12770503 DOI: 10.1016/s0168-1656(03)00068-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The expression of mumps virus nucleocapsid protein in yeast Pichia pastoris was investigated. Viral nucleocapsid proteins usually elicit a strong long-term humoral immune response in patients and experimental animals. Therefore, the detection of antibodies specific to mumps virus nucleoprotein can play an important role in immunoassays for mumps diagnosis. For producing a high-level of recombinant mumps virus nucleoprotein the expression system of yeast P. pastoris was employed. The recombinant nucleocapsid protein was purified by cesium chloride ultracentrifugation of yeast lysates. Electron microscopy of the purified recombinant nucleocapsid protein revealed a herring-bone structure similar to the one discovered in mammalian cells infected with mumps virus. The yield of purified nucleocapsid-like particles from P. pastoris constituted 2.1 mg per 1 g of wet biomass and was considerably higher in comparison to the other expression systems.
Collapse
|
25
|
Teysset L, Dang VD, Kim MK, Levin HL. A long terminal repeat-containing retrotransposon of Schizosaccharomyces pombe expresses a Gag-like protein that assembles into virus-like particles which mediate reverse transcription. J Virol 2003; 77:5451-63. [PMID: 12692246 PMCID: PMC153967 DOI: 10.1128/jvi.77.9.5451-5463.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Tf1 element of Schizosaccharomyces pombe is a long terminal repeat-containing retrotransposon that encodes functional protease, reverse transcriptase, and integrase proteins. Although these proteins are known to be necessary for protein processing, reverse transcription, and integration, respectively, the function of the protein thought to be Gag has not been determined. We present here the first electron microscopy of Tf1 particles. We tested whether the putative Gag of Tf1 was required for particle formation, packaging of RNA, and reverse transcription. We generated deletions of 10 amino acids in each of the four hydrophilic domains of the protein and found that all four mutations reduced transposition activity. The N-terminal deletion removed a nuclear localization signal and inhibited nuclear import of the transposon. The two mutations in the center of Gag destabilized the protein and resulted in no virus-like particles. The C-terminal deletion caused a defect in RNA packaging and, as a result, low levels of cDNA. The electron microscopy of cells expressing a truncated Tf1 showed that Gag alone was sufficient for the formation of virus-like particles. Taken together, these results indicate that Tf1 encodes a Gag protein that is a functional equivalent of the Gag proteins of retroviruses.
Collapse
Affiliation(s)
- Laure Teysset
- Section on Eukaryotic Transposable Elements, Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | |
Collapse
|
26
|
Cristofari G, Bampi C, Wilhelm M, Wilhelm FX, Darlix JL. A 5'-3' long-range interaction in Ty1 RNA controls its reverse transcription and retrotransposition. EMBO J 2002; 21:4368-79. [PMID: 12169639 PMCID: PMC126173 DOI: 10.1093/emboj/cdf436] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
LTR-retrotransposons are abundant components of all eukaryotic genomes and appear to be key players in their evolution. They share with retroviruses a reverse transcription step during their replication cycle. To better understand the replication of retrotransposons as well as their similarities to and differences from retroviruses, we set up an in vitro model system to examine minus-strand cDNA synthesis of the yeast Ty1 LTR-retrotransposon. Results show that the 5' and 3' ends of Ty1 genomic RNA interact through 14 nucleotide 5'-3' complementary sequences (CYC sequences). This 5'-3' base pairing results in an efficient initiation of reverse transcription in vitro. Transposition of a marked Ty1 element and Ty1 cDNA synthesis in yeast rely on the ability of the CYC sequences to base pair. This 5'-3' interaction is also supported by phylogenic analysis of all full-length Ty1 and Ty2 elements present in the Saccharomyces cerevisiae genome. These novel findings lead us to propose that circularization of the Ty1 genomic RNA controls initiation of reverse transcription and may limit reverse transcription of defective retroelements.
Collapse
Affiliation(s)
| | | | - Marcelle Wilhelm
- LaboRetro, INSERM U412, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07 and
Institut de Biologie Moléculaire et Cellulaire, 15, rue R. Descartes, 67084 Strasbourg, France Corresponding author e-mail:
| | - François-Xavier Wilhelm
- LaboRetro, INSERM U412, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07 and
Institut de Biologie Moléculaire et Cellulaire, 15, rue R. Descartes, 67084 Strasbourg, France Corresponding author e-mail:
| | - Jean-Luc Darlix
- LaboRetro, INSERM U412, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07 and
Institut de Biologie Moléculaire et Cellulaire, 15, rue R. Descartes, 67084 Strasbourg, France Corresponding author e-mail:
| |
Collapse
|
27
|
Abstract
Retrotransposition of the Ty1 element of Saccharomyces cerevisiae is temperature sensitive. Transposition activity of Ty1 is abolished at temperatures above 34 degrees C. In this report, we show that the major block to transposition at high temperature is the inhibition of processing of the Gag-Pol-p199 polyprotein and the concomitant reduction of reverse transcriptase (RT) activity. Expression of a Ty1 protease construct in Escherichia coli shows that protease enzymatic activity is inherently temperature sensitive. In yeast, Gag processing is only partially inhibited at high temperature, while cleavage of the Gag-Pol polyprotein is completely inhibited. Sites of proteolytic processing are differentially susceptible to cleavage during growth at high temperature. Overall levels of the Gag-Pol polyprotein are reduced at high temperature, although the efficiency of the requisite +1 frameshifting event appears to be increased. RT activity is inherently relatively temperature resistant, yet no cDNA is made at high temperature and the amount of RT activity is greatly reduced in virus-like particles formed at high temperature. Taken together, these results suggest that alterations in Ty1 proteins that occur at high temperature affect both protease activity and RT activity, such that Ty1 transposition is abolished.
Collapse
Affiliation(s)
- Joseph F Lawler
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | | | |
Collapse
|
28
|
Lawler JF, Merkulov GV, Boeke JD. A nucleocapsid functionality contained within the amino terminus of the Ty1 protease that is distinct and separable from proteolytic activity. J Virol 2002; 76:346-54. [PMID: 11739699 PMCID: PMC135695 DOI: 10.1128/jvi.76.1.346-354.2002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ty1 is the most successful of the five endogenous yeast retrotransposons. The life cycle of Ty1 dictates that a number of nucleocapsid (NC)-facilitated events occur although the protein(s) responsible for these events has not been identified. The positioning of the NC peptide is conserved at the carboxy terminus of the Gag protein among most long terminal repeat (LTR)-containing retroelements. An analogous region of Ty1 that simultaneously encodes part of Gag, protease (PR), and the C-terminal p4 peptide was mutagenized. Some of these mutations result in smaller-than-normal virus-like particles (VLPs). The mutants were also found to impair an NC-like functionality contained within the amino terminus of the protease that is distinct and separable from its proteolytic activity. Remarkably, these mutants have distinct defects in reverse transcription.
Collapse
Affiliation(s)
- Joseph F Lawler
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | |
Collapse
|
29
|
Lawler JF, Merkulov GV, Boeke JD. Frameshift signal transplantation and the unambiguous analysis of mutations in the yeast retrotransposon Ty1 Gag-Pol overlap region. J Virol 2001; 75:6769-75. [PMID: 11435555 PMCID: PMC114403 DOI: 10.1128/jvi.75.15.6769-6775.2001] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The yeast retrotransposon Ty1 encodes a 7-nucleotide RNA sequence that directs a programmed, +1 ribosomal frameshifting event required for Gag-Pol translation and retrotransposition. We report mutations that block frameshifting, which can be suppressed in cis by "transplanting" the frameshift signal to a position upstream of its native location. These "frameshift transplant" mutants transpose with only a modest decrease in efficiency, suggesting that the location of the frameshift signal in a functional Ty1 element may vary. The genomic architecture of Ty1 is such that Gag, Ty1 PR (PR), and the Gag-derived p4 peptide share a common sequence. The functional independence of the movement of the frameshift signal to a new location within the Ty1 element is used to unambiguously attribute the effect of mutations deleterious to transposition in this region of overlapping coding sequences to effects on the Ty1 (PR). This work defines the amino terminus of the Ty1 PR and introduces a new technique for studying viral genome organization.
Collapse
Affiliation(s)
- J F Lawler
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | |
Collapse
|
30
|
Roth JF, Kingsman SM, Kingsman AJ, Martin-Rendon E. Possible regulatory function of the Saccharomyces cerevisiae Ty1 retrotransposon core protein. Yeast 2000; 16:921-32. [PMID: 10870103 DOI: 10.1002/1097-0061(200007)16:10<921::aid-yea588>3.0.co;2-#] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The yeast Ty1 retrotransposon encodes proteins and RNA that assemble into virus-like particles (VLPs) as part of the life cycle of the retro-element. The Tya protein, which is equivalent to the retroviral Gag, is the major structural component of these particles. In this work, we demonstrate that Tya proteins fulfil other functions apart from their structural role. We show that Tya interacts in vitro with the Ty1 RNA domain required for RNA packaging, suggesting that this RNA-protein interaction may direct the packaging process. Furthermore, the overexpression of both Tya proteins, i.e. p1, the primary translation product, and p2, the mature form, increases endogenous Ty1 RNA levels in trans without increasing translation significantly. These observations suggest that Tya may exert a regulatory function during transposition. Interestingly, however, only p2, the mature form of Tya, trans-activates transposition of a marked genomic Ty element. This confirms that processing is required for transposition.
Collapse
Affiliation(s)
- J F Roth
- Retrovirus Molecular Biology Group, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | | | | | | |
Collapse
|
31
|
Abstract
Virus-like particle (VLP) assembly is a crucial step of the life cycle of retrotransposons. The S. cerevisiae Ty elements represent an interesting model for the analysis of these particles and thus have been studied extensively. Our current knowledge of the organisation and assembly of Ty1 and Ty3 VLPs is reviewed here. This includes the mechanism of assembly, the role of the Tya core protein during VLP formation and the RNA packaging process. The physical properties of Ty1 VLPs are also described and the latest three-dimensional Ty1 VLP reconstructions are shown. In addition, the relevance of these studies is discussed in the context of retro-element biology.
Collapse
Affiliation(s)
- J F Roth
- Retrovirus Molecular Biology Group, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| |
Collapse
|
32
|
AL-Khayat HA, Bhella D, Kenney JM, Roth JF, Kingsman AJ, Martin-Rendon E, Saibil HR. Yeast Ty retrotransposons assemble into virus-like particles whose T-numbers depend on the C-terminal length of the capsid protein. J Mol Biol 1999; 292:65-73. [PMID: 10493857 DOI: 10.1006/jmbi.1999.3055] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The virus-like particles (VLPs) produced by the yeast Ty retrotransposons are structurally and functionally related to retroviral cores. Using cryo-electron microscopy (cryo-EM) and three-dimensional (3D) reconstruction, we have examined the structures of VLPs assembled from full-length and truncated forms of the capsid structural protein. The VLPs are highly polydisperse in their radius distribution. We have found that the length of the C-terminal region of the capsid structural protein dictates the T -number, and thus the size, of the assembled particles. Each construct studied appears to assemble into at least two or three size classes, with shorter C termini giving rise to smaller particles. This assembly property provides a model for understanding the variable assembly of retroviral core proteins. The particles are assembled from trimer-clustered units and there are holes in the capsid shells.
Collapse
Affiliation(s)
- H A AL-Khayat
- Birkbeck College, Malet Street, London, WC1E 7HX, UK
| | | | | | | | | | | | | |
Collapse
|
33
|
Hajek KL, Friesen PD. Proteolytic processing and assembly of gag and gag-pol proteins of TED, a baculovirus-associated retrotransposon of the gypsy family. J Virol 1998; 72:8718-24. [PMID: 9765414 PMCID: PMC110286 DOI: 10.1128/jvi.72.11.8718-8724.1998] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TED (transposable element D) is an env-containing member of the gypsy family of retrotransposons that represents a possible retrovirus of invertebrates. This lepidopteran (moth) retroelement contains gag and pol genes that encode proteins capable of forming viruslike particles (VLP) with reverse transcriptase. Since VLP are likely intermediates in TED transposition, we investigated the roles of gag and pol in TED capsid assembly and maturation. By using constructed baculovirus vectors and TED Gag-specific antiserum, we show that the principal translation product of gag (Pr55(gag)) is cleaved to produce a single VLP structural protein, p37(gag). Replacement of Asp436 within the retrovirus-like active site of the pol-encoded protease (PR) abolished Pr55(gag) cleavage and demonstrated the requirement for PR in capsid processing. As shown by expression of an in-frame fusion of TED gag and pol, PR is derived from the Gag-Pol polyprotein Pr195(gag-pol). The PR cleavage site within Pr55(gag) was mapped to a position near the junction of a basic, nucleocapsid-like domain and a C-terminal acidic domain. Once released by cleavage, the C-terminal fragment was not detected. This acidic fragment was dispensable for VLP assembly, as demonstrated by the formation of VLP by C-terminal Pr55(gag) truncation proteins and replacement of the acidic domain with a heterologous protein. In contrast, C-terminal deletions that extended into the adjacent nucleocapsid-like domain of Pr55(gag) abolished VLP recovery and demonstrated that this central region contributes to VLP assembly or stability, or both. Collectively, these data suggest that the single TED protein p37(gag) provides both capsid and nucleocapsid functions. TED may therefore use a simple processing strategy for VLP assembly and genome packaging.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Cell Line
- DNA Primers/genetics
- DNA, Viral/genetics
- Endogenous Retroviruses/genetics
- Fusion Proteins, gag-pol/genetics
- Fusion Proteins, gag-pol/metabolism
- Gene Products, gag/genetics
- Gene Products, gag/metabolism
- Gene Products, pol/genetics
- Gene Products, pol/metabolism
- Genes, gag
- Genes, pol
- Kinetics
- Models, Biological
- Moths/genetics
- Moths/virology
- Mutation
- Nucleopolyhedroviruses/genetics
- Nucleopolyhedroviruses/metabolism
- Protein Processing, Post-Translational
- Retroelements
- Spodoptera
Collapse
Affiliation(s)
- K L Hajek
- Graduate Program in Cellular and Molecular Biology, Graduate School and College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | | |
Collapse
|
34
|
Ulrich R, Nassal M, Meisel H, Krüger DH. Core particles of hepatitis B virus as carrier for foreign epitopes. Adv Virus Res 1998; 50:141-82. [PMID: 9520999 DOI: 10.1016/s0065-3527(08)60808-8] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To be effective as vaccines, most monomeric proteins and peptides either require chemical coupling to high molecular weight carriers or application together with adjuvants. More recently, recombinant DNA techniques have been used to insert foreign epitopes into proteins with inherent multimerization capacity, such as particle-forming viral capsid or envelope proteins. The core protein of hepatitis B virus (HBcAg), because of its unique structural and immunological properties, has gained widespread interest as a potential antigen carrier. Foreign sequences of up to approximately 40 amino acid residues at the N terminus, 50 or 100 amino acids in the central immunodominant c/e 1 epitope region of HBcAg, and up to 100 or even more residues at the C terminus, did not interfere with particle formation. The humoral immunogenicity of inserted epitopes is determined by the immunogenicity of the peptide itself and its surface exposure, and is influenced by the route of application. The probably flexible and surface-exposed c/e1 region emerged as the most promising insertion site. When applied together with adjuvants approved for human and veterinary use, or even without adjuvants, such chimeric particles induced B and T cell immune responses against the inserted epitopes. In some cases neutralizing antibodies, cytotoxic T cells and protection against challenge with the intact pathogen were demonstrated. Major factors for the potentiated immune response against the foreign epitopes are the multimeric structure of chimeric HBcAg that results in a high epitope density per particle, and the provision of T cell help by the carrier moiety. Beyond its use as subunit vaccine, chimeric HBcAg produced in attenuated Salmonella strains may be applicable as live vaccine.
Collapse
Affiliation(s)
- R Ulrich
- Charité Medical School, Humboldt University, Berlin, Germany
| | | | | | | |
Collapse
|
35
|
Suoniemi A, Tanskanen J, Schulman AH. Gypsy-like retrotransposons are widespread in the plant kingdom. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1998; 13:699-705. [PMID: 9681012 DOI: 10.1046/j.1365-313x.1998.00071.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Retrotransposons propagate via an RNA intermediate which is then reverse-transcribed and packaged into virus-like particles. They are either copia- or gypsy-like in coding domain order and sequence similarity, the gypsy-like elements sharing their organization with the retroviruses but lacking retroviral envelope domains. Copia-like retrotransposons, or at least their reverse transcriptase domains, appear broadly distributed in higher plants, but gypsy-like elements have been reported only for scattered species. The authors have exploited the difference in domain order between these groups to amplify and clone segments bridging the reverse transcriptase-integrase region of specifically gypsy-like retrotransposons. Species representative of the diversity of higher plants yielded products whose sequences establish that gypsy-like transposons are dispersed throughout the plant genomes. This class of plant elements has been named romani retrotransposons. The presence of both types ubiquitously in the fungi, plants and animals support their existence as ancient distinct lineages and subsequent, vertical radiation.
Collapse
Affiliation(s)
- A Suoniemi
- Institute of Biotechnology, University of Helsinki, Finland
| | | | | |
Collapse
|
36
|
Garcia-Valcarcel M, Fowler WJ, Harper DR, Jeffries DJ, Layton GT. Cloning, expression, and immunogenicity of the assembly protein of varicella-zoster virus and detection of the products of open reading frame 33. J Med Virol 1997. [DOI: 10.1002/(sici)1096-9071(199712)53:4<332::aid-jmv4>3.0.co;2-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
37
|
Palmer KJ, Tichelaar W, Myers N, Burns NR, Butcher SJ, Kingsman AJ, Fuller SD, Saibil HR. Cryo-electron microscopy structure of yeast Ty retrotransposon virus-like particles. J Virol 1997; 71:6863-8. [PMID: 9261411 PMCID: PMC191967 DOI: 10.1128/jvi.71.9.6863-6868.1997] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The virus-like particles (VLPs) produced by the yeast retrotransposon Ty1 are functionally related to retroviral cores. These particles are unusual in that they have variable radif. A paired mass-radius analysis of VLPs by scanning transmission electron microscopy showed that many of these particles form an icosahedral T-number series. Three-dimensional reconstruction to 38-A resolution from cryo-electron micrographs of T = 3 and T = 4 shells revealed that the single structural protein encoded by the TYA gene assembles into spiky shells from trimeric units.
Collapse
Affiliation(s)
- K J Palmer
- Department of Crystallography, Birkbeck College, London, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
38
|
Hohjoh H, Singer MF. Ribonuclease and high salt sensitivity of the ribonucleoprotein complex formed by the human LINE-1 retrotransposon. J Mol Biol 1997; 271:7-12. [PMID: 9300051 DOI: 10.1006/jmbi.1997.1159] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
P40 is encoded by the first open reading frame of the human LINE-1 retrotransposon and is found in a large cytoplasmic ribonucleoprotein (RNP) complex, the p40 RNP-complex, in association with LINE-1 RNA(s) in human teratocarcinoma cell lines. We report here investigations on the stability of the p40 RNP-complex against various nucleases and high salt (0.5 M NaCl) treatment. The results indicate that (1) the p40 RNP-complex is dissociated after ribonuclease or high salt treatment, (2) DNase I does not disrupt the complex, (3) after dissociation of the complex, p40 maintain protein-protein interactions but in smaller complexes, and (4) p40 is not associated with the LINE-1 RNA(s) after high salt treatment. These observations suggest that the RNA molecule(s) is(are) essential for the stability of the large p40 complex and that the complex has a structure which allows various nucleases to reach the RNA. These features are distinct from those of typical virus and virus-like particles of retroviruses and other retrotransposons, respectively. Together with the fact that no significant sequence homology exists between p40 and the gag and gag-like proteins, it is likely that the p40 RNP-complex is structurally different from the typical virus and virus-like particles.
Collapse
Affiliation(s)
- H Hohjoh
- Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | |
Collapse
|
39
|
Lauermann V, Hermankova M, Boeke JD. Increased length of long terminal repeats inhibits Ty1 transposition and leads to the formation of tandem multimers. Genetics 1997; 145:911-22. [PMID: 9093846 PMCID: PMC1207896 DOI: 10.1093/genetics/145.4.911] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Ty1 retrotransposon of Saccharomyces cerevisiae is bounded by long-terminal repeats (LTRs). We have constructed a variety of Ty1 elements in which the LTR length has been increased from the normal length of 334 bp to > 2 kb. Although small insertions in the LTR have minimal effects on transposition frequency, larger insertions dramatically reduce it. Nevertheless, elements with long LTRs are incorporated into the genome at a low frequency. Most of these rare insertion events represent Ty1 tandem (head to tail) multimers.
Collapse
Affiliation(s)
- V Lauermann
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | |
Collapse
|
40
|
Merkulov GV, Swiderek KM, Brachmann CB, Boeke JD. A critical proteolytic cleavage site near the C terminus of the yeast retrotransposon Ty1 Gag protein. J Virol 1996; 70:5548-56. [PMID: 8764068 PMCID: PMC190514 DOI: 10.1128/jvi.70.8.5548-5556.1996] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cleavage of the Gag and Gag-Pol polyprotein precursors is a critical step in proliferation of retroviruses and retroelements. The Ty1 retroelement of Saccharomyces cerevisiae forms virus-like particles (VLPs) made of the Gag protein. Ty1 Gag is not obviously homologous to the Gag proteins of retroviruses. The apparent molecular mass of Gag is reduced from 58 to 54 kDa during particle maturation. Antibodies raised against the C-terminal peptide of Gag react with the 58-kDa polypeptide but not with the 54-kDa one, indicating that Gag is proteolytically processed at the C terminus. A protease cleavage site between positions 401 and 402 of the Gag precursor was defined by carboxy-terminal sequencing of the processed form of Gag. Certain deletion and substitution mutations in the C terminus of the Gag precursor result in particles that are two-thirds the diameter of the wild-type VLPs. While the Ty1 protease is active in these mutants, their transposition rates are decreased 20-fold compared with that of wild-type Ty1. Thus, the Gag C-terminal portion, released in the course of particle maturation, probably plays a significant role in VLP morphogenesis and Ty1 transposition.
Collapse
Affiliation(s)
- G V Merkulov
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21025, USA
| | | | | | | |
Collapse
|
41
|
Sandmeyer SB, Menees TM. Morphogenesis at the retrotransposon-retrovirus interface: gypsy and copia families in yeast and Drosophila. Curr Top Microbiol Immunol 1996; 214:261-96. [PMID: 8791731 DOI: 10.1007/978-3-642-80145-7_9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- S B Sandmeyer
- Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717, USA
| | | |
Collapse
|
42
|
Friant S, Heyman T, Wilhelm FX, Wilhelm M. Role of RNA primers in initiation of minus-strand and plus-strand DNA synthesis of the yeast retrotransposon Ty1. Biochimie 1996; 78:674-80. [PMID: 8955910 DOI: 10.1016/s0300-9084(96)80013-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The Ty1 retrotransposon of the yeast Saccharomyces cerevisiae is a long terminal repeat mobile genetic element that transposes through an RNA intermediate. Initiation of minus-strand and plus-strand DNA synthesis are two critical steps during reverse transcription of the retrotransposon genome. Initiation of minus-strand DNA synthesis of the Ty1 element is primed by the cytoplasmic initiator methionine tRNA base paired to the primer binding site near the 5' end of the genomic RNA. A structural probing study of the primer tRNA-Ty1 RNA binary complex reveals that besides interactions between the primer binding site and the last 10 nucleotides at the 3' end of the primer tRNA, three short regions of Ty1 RNA named box 0, box 1 and box 2.1 interact with the T and D stems and loops of the primer tRNA. Some in vivo results underline the functional importance of the nucleotide sequence of the boxes and suggest that extended interactions between genomic Ty1 RNA and the primer tRNA play a role in the reverse transcription pathway. Plus-strand DNA synthesis is initiated from an RNase H resistant oligoribonucleotide spanning a purine-rich sequence, the polypurine tract (PPT). Two sites of initiation located at the 5' boundary of the 3' long terminal repeat (PPT1) and near the middle of the TyB (pol) gene in the integrase coding sequence (PPT2) have been identified in the genome of Ty1. The two PPTs have an identical sequence, TGGGTGGTA. Mutations replacing purines by pyrimidines in this sequence significantly diminish or abolish initiation of plus-strand DNA synthesis. Ty1 elements bearing a mutated PPT2 sequence are not defective for transposition whereas mutations in PPT1 abolish transposition.
Collapse
Affiliation(s)
- S Friant
- UPR 9002 CNRS, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France
| | | | | | | |
Collapse
|
43
|
Haoudi A, Kim MH, Champion S, Best-Belpomme M, Maisonhaute C. The Gag polypeptides of the Drosophila 1731 retrotransposon are associated to virus-like particles and to nuclei. FEBS Lett 1995; 377:67-72. [PMID: 8543022 DOI: 10.1016/0014-5793(95)01305-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
1731 is a Drosophila melanogaster retrotransposon whose nucleotide sequence shows a proviral architecture with two long terminal repeats (LTRs) framing two internal Open Reading Frames (ORFs). The pol ORF2 of this mobile genetic element was demonstrated to code for an active Reverse Transcriptase (RT) and the ORF1 is expected to code for the structural Gag proteins of the virus-like particles (VLP). Using specific anti-Gag antibodies, we have characterized the 1731 Gag polypeptides expressed either in vitro or in Kc Drosophila melanogaster cultured cells. Together with the 1731 RT, the largest, likely post-translationaly-modified Gag polypeptides are gathered into cytoplasmic virus-like particles. Moreover and consistent with the nuclear localization signal present in the Gag sequence, we observed that a short 1731 Gag polypeptide is associated to the cell nuclei.
Collapse
Affiliation(s)
- A Haoudi
- Laboratoire de Genetique Cellulaire et Moleculaire, UA 1135 CNRS, Université Pierre and Marie Curie, Paris, France
| | | | | | | | | |
Collapse
|
44
|
Teng SC, Wang SX, Gabriel A. A new non-LTR retrotransposon provides evidence for multiple distinct site-specific elements in Crithidia fasciculata miniexon arrays. Nucleic Acids Res 1995; 23:2929-36. [PMID: 7659515 PMCID: PMC307132 DOI: 10.1093/nar/23.15.2929] [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: 01/26/2023] Open
Abstract
We have identified a new member of the family of trypanosome site-specific retrotransposons, using a degenerate oligonucleotide PCR strategy. The 9595 bp element, termed Crithidia retrotransposable element 2 (CRE2), was cloned and found to be inserted in the tandemly arrayed miniexon genes of Crithidia fasciculata. The element is flanked by 29 bp target site duplications but lacks the 3' poly dA tract characteristic of most other non-long terminal repeat retrotransposons. The amino terminal region of the single 2518-codon open reading frame contains a putative metal-binding motif and a proline-rich region similar to gag-like domains of other retrotransposons. The carboxy terminal region of this open reading frame shares sequence homology with the reverse transcriptase and putative endonuclease regions of three previously described trypanosomatid site-specific retrotransposons. All four of these retrotransposons are specifically inserted between nucleotides 11 and 12 of the highly conserved 39mer sequence of the miniexon gene. Most copies of CRE2 and the previously characterized CRE1 are located on different sized chromosomes. Additional CRE-related sequences were identified by screening Crithidia libraries. These results suggest that a particular sequence in the C. fasciculata miniexon repeat is the target for multiple distinct site-specific retrotransposon insertions.
Collapse
Affiliation(s)
- S C Teng
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ 08855, USA
| | | | | |
Collapse
|
45
|
Abstract
Integration of the Saccharomyces cerevisiae retrotransposon Ty1 requires the element-encoded integrase (IN) protein, which is a component of cytoplasmic virus-like particles (VLPs). Using purified recombinant Ty1 IN and an oligonucleotide integration assay based on Ty1 long terminal repeat sequences, we have compared IN activity on substrates having either wild-type or altered donor ends. IN showed a marked preference for blunt-end substrates terminating in an A:T pair over substrates ending in a G:C pair or a 3' dideoxyadenosine. VLP activity on representative substrates also showed preference for donor strands which have an adenosine terminus. Staggered-end substrates showed little activity when nucleotides were removed from the end of the wild-type donor strand, but removal of one nucleotide from the complementary strand did not significantly diminish activity. Removal of additional nucleotides from the complementary strand reduced activity to minimal detection levels. These results suggest that the sequence specificity of Ty1 IN is not stringent in vitro. The absence of Ty1 IN-mediated 3' dinucleotide cleavage, a characteristic of retroviral integrases, was demonstrated by using selected substrates. In addition to the forward reaction, both recombinant IN and VLP-associated IN carry out the reverse disintegration reaction with long terminal repeat-based dumbbell substrates. Disintegration activity exhibits sequence preferences similar to those observed for the forward reaction.
Collapse
Affiliation(s)
- S P Moore
- ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA
| | | | | |
Collapse
|
46
|
�lvarez P, S�nchez M, Molina M, Nombela C. Release of virus-like particles by osmotic shock from a mutant strain of yeast deficient in cell integrity. ACTA ACUST UNITED AC 1995. [DOI: 10.1007/bf00160833] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
47
|
Kingsman AJ, Burns NR, Layton GT, Adams SE. Yeast retrotransposon particles as antigen delivery systems. Ann N Y Acad Sci 1995; 754:202-13. [PMID: 7625653 DOI: 10.1111/j.1749-6632.1995.tb44452.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The development of technologies to produce recombinant proteins for use in the pharmaceutical industry has made substantial advances, in particular in the area of generating antigens containing multiple copies of important immunological regions. One such antigen-carrier system is based on the ability of a protein encoded by the yeast retrotransposon, Ty, to self-assemble into virus-like particles. Ty-fusion proteins retain this ability to form particles, and a range of hybrid VLPs carrying a variety of heterologous antigens have been produced and shown to induce potent immune responses. In particular, hybrid VLPs carrying the core protein p24 of HIV (p24-VLPs) have been shown to induce antibody and T-cell proliferative responses in both experimental animals and human volunteers, and immunization of rabbits with VLPs carrying the principal neutralizing determinant of HIV (V3-VLPs) resulted in the induction of neutralizing antibody responses and T-cell proliferation. Further studies with V3-VLPs have shown that this particulate antigen stimulates enhanced V3-specific lymphoproliferative responses as compared to whole recombinant gp120 or to V3 peptide conjugated to albumin. The V3-VLPs also induce potent CTL responses following immunization of mice in the absence of adjuvant. These responses are MHC class I restricted and are mediated by CD8-positive cells. These observations therefore demonstrate that hybrid Ty-VLPs induce both humoral and cellular immune responses against HIV and suggest that these immunogens may be important in combatting AIDS and other infections.
Collapse
Affiliation(s)
- A J Kingsman
- British Bio-technology Ltd., Oxford, United Kingdom
| | | | | | | |
Collapse
|
48
|
Farabaugh PJ. Post-transcriptional regulation of transposition by Ty retrotransposons of Saccharomyces cerevisiae. J Biol Chem 1995; 270:10361-4. [PMID: 7737964 DOI: 10.1074/jbc.270.18.10361] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- P J Farabaugh
- Department of Biological Sciences, University of Maryland, Baltimore 21228, USA
| |
Collapse
|
49
|
Luschnig C, Hess M, Pusch O, Brookman J, Bachmair A. The gag homologue of retrotransposon Ty1 assembles into spherical particles in Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 228:739-44. [PMID: 7737172 DOI: 10.1111/j.1432-1033.1995.0739m.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Expression of TyA (reading frame A) of the yeast retrotransposon Ty1 in Escherichia coli is possible by using efficient transcriptional and translational initiation signals. When expressed in E. coli, the gag homologue of Ty1 assembles into spherical particles similar, but not identical to virus-like particles in the natural host of Ty1, Saccharomyces cerevisiae. Deletion analysis reveals a domain in the C-terminus of TyA that is essential for the assembly process. These findings indicate that an early step of the retroelement life cycle, assembly of the gag homologue into spherical particles, does not depend on specific host factors. The experiments also demonstrate that Ty1 Gag fusion proteins, potential tools for immunization, can be produced in E. coli, an organism that lacks endogenous retrotransposons.
Collapse
Affiliation(s)
- C Luschnig
- Department of Cytology and Genetics, University of Vienna, Austria
| | | | | | | | | |
Collapse
|
50
|
Adams SE, Kingsman AJ. Retrovirus and retrotransposon particles as antigen presentation and delivery systems. PHARMACEUTICAL BIOTECHNOLOGY 1995; 6:769-86. [PMID: 7551247 DOI: 10.1007/978-1-4615-1823-5_34] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- S E Adams
- British Bio-technology Ltd., Oxford, United Kingdom
| | | |
Collapse
|