1
|
McGee AV, Liu YV, Griffith AL, Szegletes ZM, Wen B, Kraus C, Miller NW, Steger RJ, Escude Velasco B, Bosch JA, Zirin JD, Viswanatha R, Sontheimer EJ, Goodale A, Greene MA, Green TM, Doench JG. Modular vector assembly enables rapid assessment of emerging CRISPR technologies. CELL GENOMICS 2024; 4:100519. [PMID: 38484704 PMCID: PMC10943585 DOI: 10.1016/j.xgen.2024.100519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 12/31/2023] [Accepted: 02/08/2024] [Indexed: 03/19/2024]
Abstract
The diversity of CRISPR systems, coupled with scientific ingenuity, has led to an explosion of applications; however, to test newly described innovations in their model systems, researchers typically embark on cumbersome, one-off cloning projects to generate custom reagents that are optimized for their biological questions. Here, we leverage Golden Gate cloning to create the Fragmid toolkit, a modular set of CRISPR cassettes and delivery technologies, along with a web portal, resulting in a combinatorial platform that enables scalable vector assembly within days. We further demonstrate that multiple CRISPR technologies can be assessed in parallel in a pooled screening format using this resource, enabling the rapid optimization of both novel technologies and cellular models. These results establish Fragmid as a robust system for the rapid design of CRISPR vectors, and we anticipate that this assembly approach will be broadly useful for systematic development, comparison, and dissemination of CRISPR technologies.
Collapse
Affiliation(s)
- Abby V McGee
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Yanjing V Liu
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Audrey L Griffith
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Zsofia M Szegletes
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Bronte Wen
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Carolyn Kraus
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Nathan W Miller
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Ryan J Steger
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Berta Escude Velasco
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Justin A Bosch
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Jonathan D Zirin
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Raghuvir Viswanatha
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Erik J Sontheimer
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Amy Goodale
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Matthew A Greene
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Thomas M Green
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - John G Doench
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
| |
Collapse
|
2
|
McGee AV, Liu YV, Griffith AL, Szegletes ZM, Wen B, Kraus C, Miller NW, Steger RJ, Velasco BE, Bosch JA, Zirin JD, Viswanatha R, Sontheimer EJ, Goodale A, Greene MA, Green TM, Doench JG. Modular vector assembly enables rapid assessment of emerging CRISPR technologies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.25.564061. [PMID: 37961518 PMCID: PMC10634825 DOI: 10.1101/2023.10.25.564061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The diversity of CRISPR systems, coupled with scientific ingenuity, has led to an explosion of applications; however, to test newly-described innovations in their model systems, researchers typically embark on cumbersome, one-off cloning projects to generate custom reagents that are optimized for their biological questions. Here, we leverage Golden Gate cloning to create the Fragmid toolkit, a modular set of CRISPR cassettes and delivery technologies, along with a web portal, resulting in a combinatorial platform that enables scalable vector assembly within days. We further demonstrate that multiple CRISPR technologies can be assessed in parallel in a pooled screening format using this resource, enabling the rapid optimization of both novel technologies and cellular models. These results establish Fragmid as a robust system for the rapid design of CRISPR vectors, and we anticipate that this assembly approach will be broadly useful for systematic development, comparison, and dissemination of CRISPR technologies.
Collapse
Affiliation(s)
- Abby V McGee
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Yanjing V Liu
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Audrey L Griffith
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Zsofia M Szegletes
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Bronte Wen
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Carolyn Kraus
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Nathan W Miller
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Ryan J Steger
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Berta Escude Velasco
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Justin A Bosch
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Jonathan D Zirin
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Raghuvir Viswanatha
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Erik J Sontheimer
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Amy Goodale
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Matthew A Greene
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Thomas M Green
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - John G Doench
- Genetic Perturbation Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| |
Collapse
|
3
|
Zhu X, Ricci-Tam C, Hager ER, Sgro AE. Self-cleaving peptides for expression of multiple genes in Dictyostelium discoideum. PLoS One 2023; 18:e0281211. [PMID: 36862626 PMCID: PMC9980757 DOI: 10.1371/journal.pone.0281211] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 01/18/2023] [Indexed: 03/03/2023] Open
Abstract
The social amoeba Dictyostelium discoideum is a model for a wide range of biological processes including chemotaxis, cell-cell communication, phagocytosis, and development. Interrogating these processes with modern genetic tools often requires the expression of multiple transgenes. While it is possible to transfect multiple transcriptional units, the use of separate promoters and terminators for each gene leads to large plasmid sizes and possible interference between units. In many eukaryotic systems this challenge has been addressed through polycistronic expression mediated by 2A viral peptides, permitting efficient, co-regulated gene expression. Here, we screen the most commonly used 2A peptides, porcine teschovirus-1 2A (P2A), Thosea asigna virus 2A (T2A), equine rhinitis A virus 2A (E2A), and foot-and-mouth disease virus 2A (F2A), for activity in D. discoideum and find that all the screened 2A sequences are effective. However, combining the coding sequences of two proteins into a single transcript leads to notable strain-dependent decreases in expression level, suggesting additional factors regulate gene expression in D. discoideum that merit further investigation. Our results show that P2A is the optimal sequence for polycistronic expression in D. discoideum, opening up new possibilities for genetic engineering in this model system.
Collapse
Affiliation(s)
- Xinwen Zhu
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Biological Design Center, Boston University, Boston, MA, United States of America
| | - Chiara Ricci-Tam
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Biological Design Center, Boston University, Boston, MA, United States of America
| | - Emily R. Hager
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Biological Design Center, Boston University, Boston, MA, United States of America
| | - Allyson E. Sgro
- Department of Biomedical Engineering, Boston University, Boston, MA, United States of America
- Biological Design Center, Boston University, Boston, MA, United States of America
- * E-mail:
| |
Collapse
|
4
|
Wang X, Marchisio MA. Synthetic polycistronic sequences in eukaryotes. Synth Syst Biotechnol 2021; 6:254-261. [PMID: 34584993 PMCID: PMC8449083 DOI: 10.1016/j.synbio.2021.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/31/2021] [Accepted: 09/02/2021] [Indexed: 12/18/2022] Open
Abstract
The need for co-ordinate, high-level, and stable expression of multiple genes is essential for the engineering of biosynthetic circuits and metabolic pathways. This work outlines the functionality and design of IRES- and 2 A-peptide-based constructs by comparing different strategies for co-expression in polycistronic vectors. In particular, 2 A sequences are small peptides, mostly derived from viral polyproteins, that mediate a ribosome-skipping event such that several, different, separate proteins can be generated from a single open reading frame. When applied to metabolic engineering and synthetic gene circuits, 2 A peptides permit to achieve co-regulated and reliable expression of various genes in eukaryotic cells.
Collapse
Affiliation(s)
- Xuekun Wang
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, 300072, Tianjin, China
| | - Mario Andrea Marchisio
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, 300072, Tianjin, China
| |
Collapse
|
5
|
Zhang T, Li C, Cao M, Wang D, Wang Q, Xie Y, Gao S, Fu S, Zhou X, Wu J. A Novel Rice Curl Dwarf-Associated Picornavirus Encodes a 3C Serine Protease Recognizing Uncommon EPT/S Cleavage Sites. Front Microbiol 2021; 12:757451. [PMID: 34721366 PMCID: PMC8549817 DOI: 10.3389/fmicb.2021.757451] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Picornaviruses cause diseases in a wide range of vertebrates, invertebrates and plants. Here, a novel picornavirus was identified by RNA-seq technology from rice plants showing dwarfing and curling symptoms, and the name rice curl dwarf-associated virus (RCDaV) is tentatively proposed. The RCDaV genome consists of an 8,987 nt positive-stranded RNA molecule, excluding a poly(A) tail, that encodes two large polyproteins. Using in vitro cleavage assays, we have identified that the RCDaV 3C protease (3Cpro) as a serine protease recognizes the conserved EPT/S cleavage site which differs from the classic Q(E)/G(S) sites cleaved by most picornaviral 3C chymotrypsin-like cysteine proteases. Therefore, we comprehensively deciphered the RCDaV genome organization and showed that the two polyproteins of RCDaV can be cleaved into 12 mature proteins. We found that seven unclassified picornaviruses also encode a 3Cpro similar to RCDaV, and use the highly conserved EPT/S as the cleavage site. The precise genome organizations of these viruses were illustrated. Moreover, RCDaV and the seven unclassified picornaviruses share high sequence identities and similar genome organizations, and cluster into a distinct clade in the order Picornavirales. Our study provides valuable information for the understanding of picornaviral 3Cpros, deciphers the genome organization of a few relatively obscure picornaviruses, and lays the foundation for further pathogenesis research on these viruses.
Collapse
Affiliation(s)
- Tianze Zhang
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Chenyang Li
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Mengji Cao
- National Citrus Engineering and Technology Research Center, Citrus Research Institute, Southwest University, Beibei, China
| | - Dan Wang
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Qi Wang
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Yi Xie
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Shibo Gao
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Shuai Fu
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Xueping Zhou
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China.,State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jianxiang Wu
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, China.,Hainan Research Institute of Zhejiang University, Hainan, China
| |
Collapse
|
6
|
Atkins JF, O’Connor KM, Bhatt PR, Loughran G. From Recoding to Peptides for MHC Class I Immune Display: Enriching Viral Expression, Virus Vulnerability and Virus Evasion. Viruses 2021; 13:1251. [PMID: 34199077 PMCID: PMC8310308 DOI: 10.3390/v13071251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/11/2021] [Accepted: 06/19/2021] [Indexed: 01/02/2023] Open
Abstract
Many viruses, especially RNA viruses, utilize programmed ribosomal frameshifting and/or stop codon readthrough in their expression, and in the decoding of a few a UGA is dynamically redefined to specify selenocysteine. This recoding can effectively increase viral coding capacity and generate a set ratio of products with the same N-terminal domain(s) but different C-terminal domains. Recoding can also be regulatory or generate a product with the non-universal 21st directly encoded amino acid. Selection for translation speed in the expression of many viruses at the expense of fidelity creates host immune defensive opportunities. In contrast to host opportunism, certain viruses, including some persistent viruses, utilize recoding or adventitious frameshifting as part of their strategy to evade an immune response or specific drugs. Several instances of recoding in small intensively studied viruses escaped detection for many years and their identification resolved dilemmas. The fundamental importance of ribosome ratcheting is consistent with the initial strong view of invariant triplet decoding which however did not foresee the possibility of transitory anticodon:codon dissociation. Deep level dynamics and structural understanding of recoding is underway, and a high level structure relevant to the frameshifting required for expression of the SARS CoV-2 genome has just been determined.
Collapse
Affiliation(s)
- John F. Atkins
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
| | - Kate M. O’Connor
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
| | - Pramod R. Bhatt
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland
| | - Gary Loughran
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
| |
Collapse
|
7
|
Belsham GJ, Kristensen T, Jackson T. Foot-and-mouth disease virus: Prospects for using knowledge of virus biology to improve control of this continuing global threat. Virus Res 2020; 281:197909. [PMID: 32126297 DOI: 10.1016/j.virusres.2020.197909] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/28/2020] [Accepted: 02/28/2020] [Indexed: 02/06/2023]
Abstract
Understanding of the biology of foot-and-mouth disease virus (FMDV) has grown considerably since the nucleotide sequence of the viral RNA was determined. The ability to manipulate the intact genome and also to express specific parts of the genome individually has enabled detailed analyses of viral components, both RNA and protein. Such studies have identified the requirements for specific functional elements for virus replication and pathogenicity. Furthermore, information about the functions of individual virus proteins has enabled the rational design of cDNA cassettes to express non-infectious empty capsid particles that can induce protective immunity in the natural host animals and thus represent new vaccine candidates. Similarly, attempts to block specific virus activities using antiviral agents have also been performed. However, currently, only the well-established, chemically inactivated FMDV vaccines are commercially available and suitable for use to combat this important disease of livestock animals. These vaccines, despite certain shortcomings, have been used very successfully (e.g. in Europe) to control the disease but it still remains endemic in much of Africa, southern Asia and the Middle East. Hence there remains a significant risk of reintroduction of the disease into highly susceptible animal populations with enormous economic consequences.
Collapse
Affiliation(s)
- Graham J Belsham
- University of Copenhagen, Department of Veterinary and Animal Sciences, Grønnegårdsvej 15, 1870, Frederiksberg C, Denmark.
| | - Thea Kristensen
- University of Copenhagen, Department of Veterinary and Animal Sciences, Grønnegårdsvej 15, 1870, Frederiksberg C, Denmark
| | - Terry Jackson
- The Pirbright Institute, Pirbright, Woking, Surrey, GU24 0NF. UK
| |
Collapse
|
8
|
Yang X, Zeng Q, Wang M, Cheng A, Pan K, Zhu D, Liu M, Jia R, Yang Q, Wu Y, Chen S, Zhao X, Zhang S, Liu Y, Yu Y, Zhang L. DHAV-1 2A1 Peptide - A Newly Discovered Co-expression Tool That Mediates the Ribosomal "Skipping" Function. Front Microbiol 2018; 9:2727. [PMID: 30498481 PMCID: PMC6249498 DOI: 10.3389/fmicb.2018.02727] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Accepted: 10/24/2018] [Indexed: 01/27/2023] Open
Abstract
Duck hepatitis A virus 1 (DHAV-1) belongs to the genus Avihepatovirus in the family Picornaviridae. Little research has been carried out on the non-structural proteins of this virus. This study reports that 2A1 protein, the first non-structural protein on the DHAV-1 genome, has a ribosomal “skipping” function mediated by a “-GxExNPGP-” motif. In addition, we prove that when the sequence is extended 10aa to VP1 from the N-terminal of 2A1, the ribosome “skips” completely. However, as the N-terminus of 2A is shortened, the efficiency of ribosomal “skipping” reduces. When 2A1 is shortened to 10aa, it does not function. In addition, we demonstrate that N18, P19 G20, and P21 have vital roles in this function. We find that the expression of upstream and downstream proteins linked by 2A1 is different, and the expression of the upstream protein is much greater than that of the downstream protein. In addition, we demonstrate that it is the nature of 2A1 that is responsible for the expression imbalance. We also shows that the protein “cleavage” is not due to RNA “cleavage” or RNA transcription abnormalities, and the expressed protein level is independent of RNA transcriptional level. This study provides a systematic analysis of the activity of the DHAV-1 2A1 sequence and, therefore, adds to the “tool-box” that can be deployed for the co-expression applications. It provides a reference for how to apply 2A1 as a co-expression tool.
Collapse
Affiliation(s)
- Xiaoyao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Qiurui Zeng
- School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Mingshu Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Kangcheng Pan
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China
| | - Dekang Zhu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Mafeng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Renyong Jia
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Qiao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Ying Wu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Shun Chen
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xinxin Zhao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Shaqiu Zhang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yunya Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yanling Yu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Ling Zhang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Wenjiang, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.,Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| |
Collapse
|
9
|
Modifications to the Foot-and-Mouth Disease Virus 2A Peptide: Influence on Polyprotein Processing and Virus Replication. J Virol 2018; 92:JVI.02218-17. [PMID: 29386286 DOI: 10.1128/jvi.02218-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 01/20/2018] [Indexed: 12/11/2022] Open
Abstract
Foot-and-mouth disease virus (FMDV) has a positive-sense single-stranded RNA (ssRNA) genome that includes a single, large open reading frame encoding a polyprotein. The cotranslational "cleavage" of this polyprotein at the 2A/2B junction is mediated by the 2A peptide (18 residues in length) using a nonproteolytic mechanism termed "ribosome skipping" or "StopGo." Multiple variants of the 2A polypeptide with this property among the picornaviruses share a conserved C-terminal motif [D(V/I)E(S/T)NPG↓P]. The impact of 2A modifications within this motif on FMDV protein synthesis, polyprotein processing, and virus viability were investigated. Amino acid substitutions are tolerated at residues E14, S15, and N16 within the 2A sequences of infectious FMDVs despite their reported "cleavage" efficiencies at the 2A/2B junction of only ca. 30 to 50% compared to that of the wild type (wt). In contrast, no viruses containing substitutions at residue P17, G18, or P19, which displayed little or no "cleavage" activity in vitro, were rescued, but wt revertants were obtained. The 2A substitutions impaired the replication of an FMDV replicon. Using transient-expression assays, it was shown that certain amino acid substitutions at residues E14, S15, N16, and P19 resulted in partial "cleavage" of a protease-free polyprotein, indicating that these specific residues are not essential for cotranslational "cleavage." Immunofluorescence studies, using full-length FMDV RNA transcripts encoding mutant 2A peptides, indicated that the 2A peptide remained attached to adjacent proteins, presumably 2B. These results show that efficient "cleavage" at the 2A/2B junction is required for optimal virus replication. However, maximal StopGo activity does not appear to be essential for the viability of FMDV.IMPORTANCE Foot-and-mouth disease virus (FMDV) causes one of the most economically important diseases of farm animals. Cotranslational "cleavage" of the FMDV polyprotein precursor at the 2A/2B junction, termed StopGo, is mediated by the short 2A peptide through a nonproteolytic mechanism which leads to release of the nascent protein and continued translation of the downstream sequence. Improved understanding of this process will not only give a better insight into how this peptide influences the FMDV replication cycle but may also assist the application of this sequence in biotechnology for the production of multiple proteins from a single mRNA. Our data show that single amino acid substitutions in the 2A peptide can have a major influence on viral protein synthesis, virus viability, and polyprotein processing. They also indicate that efficient "cleavage" at the 2A/2B junction is required for optimal virus replication. However, maximal StopGo activity is not essential for the viability of FMDV.
Collapse
|
10
|
Abstract
Reproduction of RNA viruses is typically error-prone due to the infidelity of their replicative machinery and the usual lack of proofreading mechanisms. The error rates may be close to those that kill the virus. Consequently, populations of RNA viruses are represented by heterogeneous sets of genomes with various levels of fitness. This is especially consequential when viruses encounter various bottlenecks and new infections are initiated by a single or few deviating genomes. Nevertheless, RNA viruses are able to maintain their identity by conservation of major functional elements. This conservatism stems from genetic robustness or mutational tolerance, which is largely due to the functional degeneracy of many protein and RNA elements as well as to negative selection. Another relevant mechanism is the capacity to restore fitness after genetic damages, also based on replicative infidelity. Conversely, error-prone replication is a major tool that ensures viral evolvability. The potential for changes in debilitated genomes is much higher in small populations, because in the absence of stronger competitors low-fit genomes have a choice of various trajectories to wander along fitness landscapes. Thus, low-fit populations are inherently unstable, and it may be said that to run ahead it is useful to stumble. In this report, focusing on picornaviruses and also considering data from other RNA viruses, we review the biological relevance and mechanisms of various alterations of viral RNA genomes as well as pathways and mechanisms of rehabilitation after loss of fitness. The relationships among mutational robustness, resilience, and evolvability of viral RNA genomes are discussed.
Collapse
|