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Giacchello I, Musumeci F, D'Agostino I, Greco C, Grossi G, Schenone S. Insights into RNA-dependent RNA Polymerase Inhibitors as Antiinfluenza Virus Agents. Curr Med Chem 2021; 28:1068-1090. [PMID: 31942843 DOI: 10.2174/0929867327666200114115632] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/21/2019] [Accepted: 12/22/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Influenza is a seasonal disease that affects millions of people every year and has a significant economic impact. Vaccines are the best strategy to fight this viral pathology, but they are not always available or administrable, prompting the search for antiviral drugs. RNA-dependent RNA polymerase (RdRp) recently emerged as a promising target because of its key role in viral replication and its high conservation among viral strains. DISCUSSION This review presents an overview of the most interesting RdRp inhibitors that have been discussed in the literature since 2000. Compounds already approved or in clinical trials and a selection of inhibitors endowed with different scaffolds are described, along with the main features responsible for their activity. RESULTS RdRp inhibitors are emerging as a new strategy to fight viral infections and the importance of this class of drugs has been confirmed by the FDA approval of baloxavir marboxil in 2018. Despite the complexity of the RdRp machine makes the identification of new compounds a challenging research topic, it is likely that in the coming years, this field will attract the interest of a number of academic and industrial scientists because of the potential strength of this therapeutic approach.
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Affiliation(s)
- Ilaria Giacchello
- Department of Pharmacy, University of Genoa, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Francesca Musumeci
- Department of Pharmacy, University of Genoa, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Ilaria D'Agostino
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Chiara Greco
- Department of Pharmacy, University of Genoa, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Giancarlo Grossi
- Department of Pharmacy, University of Genoa, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Silvia Schenone
- Department of Pharmacy, University of Genoa, Viale Benedetto XV, 3, 16132 Genoa, Italy
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Lutz MM, Dunagan MM, Kurebayashi Y, Takimoto T. Key Role of the Influenza A Virus PA Gene Segment in the Emergence of Pandemic Viruses. Viruses 2020; 12:v12040365. [PMID: 32224899 PMCID: PMC7232137 DOI: 10.3390/v12040365] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 03/24/2020] [Indexed: 12/18/2022] Open
Abstract
Influenza A viruses (IAVs) are a significant human pathogen that cause seasonal epidemics and occasional pandemics. Avian waterfowl are the natural reservoir of IAVs, but a wide range of species can serve as hosts. Most IAV strains are adapted to one host species and avian strains of IAV replicate poorly in most mammalian hosts. Importantly, IAV polymerases from avian strains function poorly in mammalian cells but host adaptive mutations can restore activity. The 2009 pandemic H1N1 (H1N1pdm09) virus acquired multiple mutations in the PA gene that activated polymerase activity in mammalian cells, even in the absence of previously identified host adaptive mutations in other polymerase genes. These mutations in PA localize within different regions of the protein suggesting multiple mechanisms exist to activate polymerase activity. Additionally, an immunomodulatory protein, PA-X, is expressed from the PA gene segment. PA-X expression is conserved amongst many IAV strains but activity varies between viruses specific for different hosts, suggesting that PA-X also plays a role in host adaptation. Here, we review the role of PA in the emergence of currently circulating H1N1pdm09 viruses and the most recent studies of host adaptive mutations in the PA gene that modulate polymerase activity and PA-X function.
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Affiliation(s)
- Michael M. Lutz
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Megan M. Dunagan
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Yuki Kurebayashi
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka-shi 422-8526, Japan
| | - Toru Takimoto
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Correspondence: ; Tel.: +1-585-273-2856
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Rodriguez P, Marcos-Villar L, Zamarreño N, Yángüez E, Nieto A. Mutations of the segment-specific nucleotides at the 3' end of influenza virus NS segment control viral replication. Virology 2019; 539:104-113. [PMID: 31706162 DOI: 10.1016/j.virol.2019.10.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 11/28/2022]
Abstract
The vRNAs of influenza A viruses contain 12 and 13 nucleotide-long sequences at their 3' and 5' termini respectively that are highly conserved and constitute the vRNA promoter. These sequences and the next three segment-specific nucleotides show inverted partial complementarity and are followed by several unpaired nucleotides of poorly characterized function at the 3' end. We have performed systematic point-mutations at the segment-specific nucleotides 15-18 of the 3'-end of a NS-like vRNA segment. All NS-like vRNAs containing mutations at position 15, and some at positions 16-18 showed reduced transcription/replication efficiency in a transfection/infection system. In addition, the replication of recombinant viruses containing mutations at position 15 was impaired both in single and multi-cycle experiments. This reduction was the consequence of a decreased expression of the NS segment. The data indicate that NS1 plays a role in the transcription/replication of its own segment, which elicits a global defect on virus replication.
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Affiliation(s)
- Paloma Rodriguez
- Centro Nacional de Biotecnología, C.S.I.C. Darwin 3, Cantoblanco, 28049, Madrid, Spain; CIBER de Enfermedades Respiratorias CIBERES, Spain
| | - Laura Marcos-Villar
- Centro Nacional de Biotecnología, C.S.I.C. Darwin 3, Cantoblanco, 28049, Madrid, Spain; CIBER de Enfermedades Respiratorias CIBERES, Spain
| | - Noelia Zamarreño
- Centro Nacional de Biotecnología, C.S.I.C. Darwin 3, Cantoblanco, 28049, Madrid, Spain; CIBER de Enfermedades Respiratorias CIBERES, Spain
| | - Emilio Yángüez
- Centro Nacional de Biotecnología, C.S.I.C. Darwin 3, Cantoblanco, 28049, Madrid, Spain; CIBER de Enfermedades Respiratorias CIBERES, Spain
| | - Amelia Nieto
- Centro Nacional de Biotecnología, C.S.I.C. Darwin 3, Cantoblanco, 28049, Madrid, Spain; CIBER de Enfermedades Respiratorias CIBERES, Spain.
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4
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Kim IH, Choi JG, Lee YJ, Kwon HJ, Kim JH. Effects of different polymerases of avian influenza viruses on the growth and pathogenicity of A/Puerto Rico/8/1934 (H1N1)-derived reassorted viruses. Vet Microbiol 2013; 168:41-9. [PMID: 24296300 DOI: 10.1016/j.vetmic.2013.10.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/11/2013] [Accepted: 10/17/2013] [Indexed: 11/27/2022]
Abstract
We generated reassorted PR8 viruses containing six different combinations of avian influenza virus (AIV) polymerase genes from A/chicken/Korea/01310/2001 (H9N2) (01310) and A/chicken/Korea/KBNP-0028/2000 (H9N2) (0028) to examine the effects of the AIV polymerase genes PB1, PB2, and PA on replication efficiency in different host cells and pathogenicity in mice. The virus titers of the reassorted viruses possessing 01310 [rPR8-PB2(01310)] and 0028 [rPR8-PB2(0028)] PB2 genes were significantly higher than those of the others except the rPR8 virus in embryonated chicken eggs at 37°C, and those of avian polymerase reassorted viruses were significantly less than rPR8 in MDCK cells at 32 and 37°C. rPR8-PB2(01310), rPR8-PB2(0028), and rPR8-PA(0028) caused no body weight loss in BALB/c mice but rPR8-PA(01310), rPR8-PB1(01310), and rPR8-PB1(0028) caused mortality and significantly different body weight loss compared to those in the mock treatment. In contrast to rPR8-PB2(0028) and rPR8-PA(0028), rPR8-PB2(01310) was not isolated from infected mice, and rPR8-PB1(0028) was less pathogenic than rPR8-PB1(01310). We determined the amino acid residues that were specific to the less pathogenic polymerases. A comparison with those of pandemic 2009 H1N1, human fatal H5N1 and H7N9, and pathogenic AIVs to mice without adaptation revealed that they possessed the mammalian pathogenic constellation of polymerases. Thus, the novel polymerase genes and amino acid residues may be useful to understand the host-barrier overcome of AIVs in mice and to develop safer and efficacious vaccines.
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Affiliation(s)
- Il-Hwan Kim
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea; Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea
| | - Jun-Gu Choi
- Avian Disease Division, Animal and Plant Quarantine Agency, 175 Anyangro, Manan-gu, Anyangsi, Gyeonggido 430-757, Republic of Korea
| | - Youn-Jeong Lee
- Avian Disease Division, Animal and Plant Quarantine Agency, 175 Anyangro, Manan-gu, Anyangsi, Gyeonggido 430-757, Republic of Korea
| | - Hyuk-Joon Kwon
- Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea.
| | - Jae-Hong Kim
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea; Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Republic of Korea.
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5
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Abstract
Many replication events are involved in the influenza A virus life cycle, and they are accomplished by different virus proteins with specific functions. However, because the size of the influenza virus genome is limited, the virus uses different mechanisms to express multiple viral proteins from a single gene segment. The M2 and NS2 proteins are produced by splicing, and several novel influenza A virus proteins, such as PB1-F2, PB1-N40, and PA-X, have recently been identified. Here, we identified novel PA-related proteins in influenza A virus-infected cells. These newly identified proteins are translated from the 11th and 13th in-frame AUG codons in the PA mRNA and are, therefore, N-terminally truncated forms of PA, which we named PA-N155 and PA-N182, respectively. The 11th and 13th AUG codons are highly conserved among influenza A viruses, and the PA-N155 and PA-N182 proteins were detected in cells infected with various influenza A viruses isolated from different host species, suggesting the expression of these N-truncated PAs is universal in nature among influenza A viruses. These N-truncated PAs did not show polymerase activity when expressed together with PB1 and PB2; however, mutant viruses lacking the N-truncated PAs replicated more slowly in cell culture and had lower pathogenicity in mice than did wild-type virus. These results suggest that these novel PA-related proteins likely possess important functions in the replication cycle of influenza A virus.
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6
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Cellular protein HAX1 interacts with the influenza A virus PA polymerase subunit and impedes its nuclear translocation. J Virol 2012; 87:110-23. [PMID: 23055567 DOI: 10.1128/jvi.00939-12] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Transcription and replication of the influenza A virus RNA genome occur in the nucleus through the viral RNA-dependent RNA polymerase consisting of PB1, PB2, and PA. Cellular factors that associate with the viral polymerase complex play important roles in these processes. To look for cellular factors that could associate with influenza A virus PA protein, we have carried out a yeast two-hybrid screen using a HeLa cell cDNA library. We identified six cellular proteins that may interact with PA. We focused our study on one of the new PA-interacting proteins, HAX1, a protein with antiapoptotic function. By using glutathione S-transferase pulldown and coimmunoprecipitation assays, we demonstrate that HAX1 specifically interacts with PA in vitro and in vivo and that HAX1 interacts with the nuclear localization signal domain of PA. Nuclear accumulation of PA was increased in HAX1-knockdown cells, and this phenotype could be reversed by reexpression of HAX1, indicating that HAX1 can impede nuclear transport of PA. As a consequence, knockdown of HAX1 resulted in a significant increase in virus yield and polymerase activity in a minigenome assay, and this phenotype could be reversed by reexpression of HAX1, indicating that HAX1 can inhibit influenza A virus propagation. Together, these results not only provide insight into the mechanism underlying nuclear transport of PA but also identify an intrinsic host factor that restricts influenza A virus infection.
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7
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Improved sensitivity of influenza A antigen detection using a combined NP, M, and NS1 sandwich ELISA. J Virol Methods 2012; 185:24-31. [PMID: 22677225 DOI: 10.1016/j.jviromet.2012.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 05/21/2012] [Accepted: 05/24/2012] [Indexed: 11/21/2022]
Abstract
A new modified triple-antigen detection test was developed for the direct detection of the influenza A virus. The nucleoprotein (NP), matrix (M), and non-structural (NS1) proteins were used as target antigens because they are abundant in infected cells. Monoclonal antibodies specific to the NP, M, and NS1 proteins were generated. The antibody pairs were selected and evaluated for their reactivity individually and in combination in the triple-antigen detection using sandwich ELISA. Triple-antigen detection demonstrated a higher sensitivity than individual antigen detection when tested with both the H1N1 and H3N2 influenza A viruses. This was illustrated by the 4-fold lower limit of detection of the triple-antigen test than the individual antigen detection test. The findings demonstrated that the sensitivity of influenza A antigen detection was improved with the triple-antigen detection system as compared to individual antigen detection. Therefore, this technique could be a useful tool for the direct detection of cell-associated influenza A antigen. Furthermore, it could provide a basis for the development of a rapid triple-antigen test for influenza A diagnosis.
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8
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Hutchinson EC, Fodor E. Nuclear import of the influenza A virus transcriptional machinery. Vaccine 2012; 30:7353-8. [PMID: 22652398 DOI: 10.1016/j.vaccine.2012.04.085] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 04/24/2012] [Indexed: 11/18/2022]
Abstract
Unusually for an RNA virus, influenza A viruses transcribe and replicate their genomes in the nuclei of infected cells. As a result the viral ribonucleoprotein complexes (RNPs), and their newly synthesised protein subunits, must interact with the host nuclear import machinery. In this review we discuss how the virus exploits nuclear import pathways to allow regulated and chaperoned assembly of RNPs in the nucleus, and describe how the import machinery itself can be a determinant of host tropism.
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Affiliation(s)
- E C Hutchinson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
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9
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Cheng VCC, To KKW, Tse H, Hung IFN, Yuen KY. Two years after pandemic influenza A/2009/H1N1: what have we learned? Clin Microbiol Rev 2012; 25:223-63. [PMID: 22491771 PMCID: PMC3346300 DOI: 10.1128/cmr.05012-11] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The world had been anticipating another influenza pandemic since the last one in 1968. The pandemic influenza A H1N1 2009 virus (A/2009/H1N1) finally arrived, causing the first pandemic influenza of the new millennium, which has affected over 214 countries and caused over 18,449 deaths. Because of the persistent threat from the A/H5N1 virus since 1997 and the outbreak of the severe acute respiratory syndrome (SARS) coronavirus in 2003, medical and scientific communities have been more prepared in mindset and infrastructure. This preparedness has allowed for rapid and effective research on the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the disease, with impacts on its control. A PubMed search using the keywords "pandemic influenza virus H1N1 2009" yielded over 2,500 publications, which markedly exceeded the number published on previous pandemics. Only representative works with relevance to clinical microbiology and infectious diseases are reviewed in this article. A significant increase in the understanding of this virus and the disease within such a short amount of time has allowed for the timely development of diagnostic tests, treatments, and preventive measures. These findings could prove useful for future randomized controlled clinical trials and the epidemiological control of future pandemics.
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Affiliation(s)
- Vincent C C Cheng
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
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10
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MacDonald LA, Aggarwal S, Bussey KA, Desmet EA, Kim B, Takimoto T. Molecular interactions and trafficking of influenza A virus polymerase proteins analyzed by specific monoclonal antibodies. Virology 2012; 426:51-9. [PMID: 22325937 DOI: 10.1016/j.virol.2012.01.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2011] [Revised: 01/04/2012] [Accepted: 01/17/2012] [Indexed: 12/21/2022]
Abstract
The influenza polymerase complex composed of PA, PB1 and PB2, plays a key role in viral replication and pathogenicity. Newly synthesized components must be translocated to the nucleus, where replication and transcription of viral genomes take place. Previous studies suggest that while PB2 is translocated to the nucleus independently, PA and PB1 subunits could not localize to the nucleus unless in a PA-PB1 complex. To further determine the molecular interactions between the components, we created a panel of 16 hybridoma cell lines, which produce monoclonal antibodies (mAbs) against each polymerase component. We showed that, although PB1 interacts with both PA and PB2 individually, nuclear localization of PB1 is enhanced only when co-expressed with PA. Interestingly, one of the anti-PA mAbs reacted much more strongly with PA when co-expressed with PB1. These results suggest that PA-PB1 interactions induce a conformational change in PA, which could be required for its nuclear translocation.
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Affiliation(s)
- Leslie A MacDonald
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
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11
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Liang Y, Danzy S, Dao LD, Parslow TG, Liang Y. Mutational analyses of the influenza A virus polymerase subunit PA reveal distinct functions related and unrelated to RNA polymerase activity. PLoS One 2012; 7:e29485. [PMID: 22238617 PMCID: PMC3253111 DOI: 10.1371/journal.pone.0029485] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 11/29/2011] [Indexed: 11/19/2022] Open
Abstract
Influenza A viral polymerase is a heterotrimeric complex that consists of PA, PB1, and PB2 subunits. We previously reported that a di-codon substitution mutation (G507A-R508A), denoted J10, in the C-terminal half of PA had no apparent effect on viral RNA synthesis but prevented infectious virus production, indicating that PA may have a novel role independent of its polymerase activity. To further examine the roles of PA in the viral life cycle, we have now generated and characterized additional mutations in regions flanking the J10 site from residues 497 to 518. All tested di-codon mutations completely abolished or significantly reduced viral infectivity, but they did so through disparate mechanisms. Several showed effects resembling those of J10, in that the mutant polymerase supported normal levels of viral RNA synthesis but nonetheless failed to generate infectious viral particles. Others eliminated polymerase activity, in most cases by perturbing the normal nuclear localization of PA protein in cells. We also engineered single-codon mutations that were predicted to pack near the J10 site in the crystal structure of PA, and found that altering residues K378 or D478 each produced a J10-like phenotype. In further studies of J10 itself, we found that this mutation does not affect the formation and release of virion-like particles per se, but instead impairs the ability of those particles to incorporate each of the eight essential RNA segments (vRNAs) that make up the viral genome. Taken together, our analysis identifies mutations in the C-terminal region of PA that differentially affect at least three distinct activities: protein nuclear localization, viral RNA synthesis, and a trans-acting function that is required for efficient packaging of all eight vRNAs.
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Affiliation(s)
- Yuhong Liang
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Shamika Danzy
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Luan Danh Dao
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Tristram G. Parslow
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Yuying Liang
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
- * E-mail:
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Hutchinson EC, Orr OE, Man Liu S, Engelhardt OG, Fodor E. Characterization of the interaction between the influenza A virus polymerase subunit PB1 and the host nuclear import factor Ran-binding protein 5. J Gen Virol 2011; 92:1859-1869. [DOI: 10.1099/vir.0.032813-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The influenza A virus RNA polymerase is a heterotrimer that transcribes and replicates the viral genome in the cell nucleus. Newly synthesized RNA polymerase subunits must therefore be imported into the nucleus during an infection. While various models have been proposed for this process, the consensus is that the polymerase basic protein PB1 and polymerase acidic protein PA subunits form a dimer in the cytoplasm and are transported into the nucleus by the beta-importin Ran-binding protein 5 (RanBP5), with the PB2 subunit imported separately to complete the trimeric complex. In this study, we characterized the interaction of PB1 with RanBP5 further and assessed its importance for viral growth. In particular, we found that the N-terminal region of PB1 mediates its binding to RanBP5 and that basic residues in a nuclear localization signal are required for RanBP5 binding. Mutating these basic residues to alanines does not prevent PB1 forming a dimer with PA, but does reduce RanBP5 binding. RanBP5-binding mutations reduce, though do not entirely prevent, the nuclear accumulation of PB1. Furthermore, mutations affecting RanBP5 binding are incompatible with or severely attenuate viral growth, providing further support for a key role for RanBP5 in the influenza A virus life cycle.
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Affiliation(s)
| | - Olivia E. Orr
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Sai Man Liu
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Ervin Fodor
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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Deng Q, Wang D, Xiang X, Gao X, Hardwidge PR, Kaushik R, Wolff T, Chakravarty S, Li F. Nuclear localization of influenza B polymerase proteins and their binary complexes. Virus Res 2011; 156:49-53. [PMID: 21215284 DOI: 10.1016/j.virusres.2010.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 01/17/2023]
Abstract
The viral RNA-dependent RNA polymerases of influenza A and B are trimeric complexes of PA, PB1, and PB2 subunits that are crucial for both transcription and replication of the viral genome. Unlike the significant progress made recently in understanding nuclear transport and molecular assembly of influenza A polymerase, little is known about the influenza B polymerase, although influenza B viruses cause severe upper respiratory disease in humans. The aim of this study was to characterize nuclear localization of the influenza B RNA polymerase proteins and binary complexes. We demonstrated that each polymerase protein has a nuclear localization function, and among them, the PB2 protein exclusively locates to the nucleus while PA and PB1 proteins are associated with the cytoplasm and the nucleus. Furthermore, we show that pairwise binary complexes are formed among the influenza B subunits (PA-PB1, PA-PB2, and PB1-PB2) and both PB1-PB2 and PA-PB2 complexes are predominantly associated with the nucleus while the PA-PB1 complex exhibits both nuclear and cytoplasmic fluorescence signals. Results of our studies represent the first step toward the understanding of nuclear transport and molecular assembly within the influenza B polymerase complex.
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Affiliation(s)
- Qiji Deng
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, United States
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14
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A complicated message: Identification of a novel PB1-related protein translated from influenza A virus segment 2 mRNA. J Virol 2009; 83:8021-31. [PMID: 19494001 DOI: 10.1128/jvi.00826-09] [Citation(s) in RCA: 268] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Influenza A virus segment 2 is known to encode two polypeptides in overlapping open reading frames: PB1, the polymerase, and PB1-F2, a proapoptotic virulence factor. We show that a third major polypeptide is synthesized from PB1 mRNA via differential AUG codon usage. PB1 codon 40 directs translation of an N-terminally truncated version of the polypeptide (N40) that lacks transcriptase function but nevertheless interacts with PB2 and the polymerase complex in the cellular environment. Importantly, the expression of N40, PB1-F2, and PB1 are interdependent, and certain mutations previously used to ablate PB1-F2 production affected N40 accumulation. Removal of the PB1-F2 AUG upregulated N40 synthesis, while truncating PB1-F2 after codon 8 (with a concomitant M40I change in PB1) abolished N40 expression. A virus lacking both N40 and PB1-F2 replicated normally. However, viruses that did not express N40 but retained an intact PB1-F2 gene overexpressed PB1 early in infection and replicated slowly in tissue culture. Thus, the influenza A virus proteome includes a 12th primary translation product that (similarly to PB1-F2) is nonessential for virus viability but whose loss, in particular genetic backgrounds, is detrimental to virus replication.
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15
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Yuan P, Bartlam M, Lou Z, Chen S, Zhou J, He X, Lv Z, Ge R, Li X, Deng T, Fodor E, Rao Z, Liu Y. Crystal structure of an avian influenza polymerase PA(N) reveals an endonuclease active site. Nature 2009; 458:909-13. [PMID: 19194458 DOI: 10.1038/nature07720] [Citation(s) in RCA: 396] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 12/12/2008] [Indexed: 12/24/2022]
Abstract
The heterotrimeric influenza virus polymerase, containing the PA, PB1 and PB2 proteins, catalyses viral RNA replication and transcription in the nucleus of infected cells. PB1 holds the polymerase active site and reportedly harbours endonuclease activity, whereas PB2 is responsible for cap binding. The PA amino terminus is understood to be the major functional part of the PA protein and has been implicated in several roles, including endonuclease and protease activities as well as viral RNA/complementary RNA promoter binding. Here we report the 2.2 ångström (A) crystal structure of the N-terminal 197 residues of PA, termed PA(N), from an avian influenza H5N1 virus. The PA(N) structure has an alpha/beta architecture and reveals a bound magnesium ion coordinated by a motif similar to the (P)DX(N)(D/E)XK motif characteristic of many endonucleases. Structural comparisons and mutagenesis analysis of the motif identified in PA(N) provide further evidence that PA(N) holds an endonuclease active site. Furthermore, functional analysis with in vivo ribonucleoprotein reconstitution and direct in vitro endonuclease assays strongly suggest that PA(N) holds the endonuclease active site and has critical roles in endonuclease activity of the influenza virus polymerase, rather than PB1. The high conservation of this endonuclease active site among influenza strains indicates that PA(N) is an important target for the design of new anti-influenza therapeutics.
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Affiliation(s)
- Puwei Yuan
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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Bradel-Tretheway BG, Kelley Z, Chakraborty-Sett S, Takimoto T, Kim B, Dewhurst S. The human H5N1 influenza A virus polymerase complex is active in vitro over a broad range of temperatures, in contrast to the WSN complex, and this property can be attributed to the PB2 subunit. J Gen Virol 2009; 89:2923-2932. [PMID: 19008377 PMCID: PMC3067610 DOI: 10.1099/vir.0.2008/006254-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Influenza A virus (IAV) replicates in the upper respiratory tract of humans at 33 degrees C and in the intestinal tract of birds at close to 41 degrees C. The viral RNA polymerase complex comprises three subunits (PA, PB1 and PB2) and plays an important role in host adaptation. We therefore developed an in vitro system to examine the temperature sensitivity of IAV RNA polymerase complexes from different origins. Complexes were prepared from human lung epithelial cells (A549) using a novel adenoviral expression system. Affinity-purified complexes were generated that contained either all three subunits (PA/PB1/PB2) from the A/Viet/1203/04 H5N1 virus (H/H/H) or the A/WSN/33 H1N1 strain (W/W/W). We also prepared chimeric complexes in which the PB2 subunit was exchanged (H/H/W, W/W/H) or substituted with an avian PB2 from the A/chicken/Nanchang/3-120/01 H3N2 strain (W/W/N). All complexes were functional in transcription, cap-binding and endonucleolytic activity. Complexes containing the H5N1 or Nanchang PB2 protein retained transcriptional activity over a broad temperature range (30-42 degrees C). In contrast, complexes containing the WSN PB2 protein lost activity at elevated temperatures (39 degrees C or higher). The E627K mutation in the avian PB2 was not required for this effect. Finally, the avian PB2 subunit was shown to confer enhanced stability to the WSN 3P complex. These results show that PB2 plays an important role in regulating the temperature optimum for IAV RNA polymerase activity, possibly due to effects on the functional stability of the 3P complex.
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Affiliation(s)
- Birgit G Bradel-Tretheway
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Z Kelley
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Shikha Chakraborty-Sett
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Toru Takimoto
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Baek Kim
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Stephen Dewhurst
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
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17
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Gabriel G, Herwig A, Klenk HD. Interaction of polymerase subunit PB2 and NP with importin alpha1 is a determinant of host range of influenza A virus. PLoS Pathog 2008; 4:e11. [PMID: 18248089 PMCID: PMC2222953 DOI: 10.1371/journal.ppat.0040011] [Citation(s) in RCA: 286] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2007] [Accepted: 12/10/2007] [Indexed: 12/31/2022] Open
Abstract
We have previously reported that mutations in the polymerase proteins PB1, PB2, PA, and the nucleocapsid protein NP resulting in enhanced transcription and replication activities in mammalian cells are responsible for the conversion of the avian influenza virus SC35 (H7N7) into the mouse-adapted variant SC35M. We show now that adaptive mutations D701N in PB2 and N319K in NP enhance binding of these proteins to importin α1 in mammalian cells. Enhanced binding was paralleled by transient nuclear accumulation and cytoplasmic depletion of importin α1 as well as increased transport of PB2 and NP into the nucleus of mammalian cells. In avian cells, enhancement of importin α1 binding and increased nuclear transport were not observed. These findings demonstrate that adaptation of the viral polymerase to the nuclear import machinery plays an important role in interspecies transmission of influenza virus. The natural hosts of influenza A viruses are aquatic birds. On rare occasions these viruses may be transmitted to humans and then give rise to an influenza pandemic. Human influenza is therefore a typical re-emerging infection. Evidence is increasing that the viral polymerase, an enzyme that has to enter into the nucleus of the infected cell in order to promote replication and transcription of the viral genome, is a major determinant of host range. Thus, in a comparative study of an avian influenza strain and its mouse adapted variant we have previously shown that adaptation to mice depended exclusively on mutations in the polymerase proteins. These findings supported the concept that adaptation of the polymerase to host factors is an important mechanism underlying interspecies transmission. In the present study, we have identified importin α1, a component of the nuclear pore complex, as such a host factor. We show that adaptive mutations in polymerase subunits improve binding to importin α1 in mammalian, but not in avian cells. As a result, nuclear transport of these proteins and efficiency of replication are enhanced in mammalian cells. These observations demonstrate that the interaction of the viral polymerase with the nuclear import machinery is an important determinant of host range.
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Affiliation(s)
- Gülsah Gabriel
- Institute of Virology, Philipps University Marburg, Germany
| | - Astrid Herwig
- Institute of Virology, Philipps University Marburg, Germany
| | - Hans-Dieter Klenk
- Institute of Virology, Philipps University Marburg, Germany
- * To whom correspondence should be addressed. E-mail:
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18
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Abstract
The outbreaks of avian influenza A virus in poultry and humans over the last decade posed a pandemic threat to human. Here, we discuss the basic classification and the structure of influenza A virus. The viral genome contains eight RNA viral segments and the functions of viral proteins encoded by this genome are described. In addition, the RNA transcription and replication of this virus are reviewed.
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Affiliation(s)
- Timothy K W Cheung
- Department of Microbiology, University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong, China
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19
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Tarendeau F, Boudet J, Guilligay D, Mas PJ, Bougault CM, Boulo S, Baudin F, Ruigrok RWH, Daigle N, Ellenberg J, Cusack S, Simorre JP, Hart DJ. Structure and nuclear import function of the C-terminal domain of influenza virus polymerase PB2 subunit. Nat Struct Mol Biol 2007; 14:229-33. [PMID: 17310249 DOI: 10.1038/nsmb1212] [Citation(s) in RCA: 247] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 01/31/2007] [Indexed: 11/08/2022]
Abstract
The trimeric influenza virus polymerase, comprising subunits PA, PB1 and PB2, is responsible for transcription and replication of the segmented viral RNA genome. Using a novel library-based screening technique called expression of soluble proteins by random incremental truncation (ESPRIT), we identified an independently folded C-terminal domain from PB2 and determined its solution structure by NMR. Using green fluorescent protein fusions, we show that both the domain and the full-length PB2 subunit are efficiently imported into the nucleus dependent on a previously overlooked bipartite nuclear localization sequence (NLS). The crystal structure of the domain complexed with human importin alpha5 shows how the last 20 residues unfold to permit binding to the import factor. The domain contains three surface residues implicated in adaptation from avian to mammalian hosts. One of these tethers the NLS-containing peptide to the core of the domain in the unbound state.
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Affiliation(s)
- Franck Tarendeau
- European Molecular Biology Laboratory (EMBL) Grenoble Outstation, 6 rue Jules Horowitz, BP181, 38042 Grenoble Cedex 9, France
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20
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Naito T, Momose F, Kawaguchi A, Nagata K. Involvement of Hsp90 in assembly and nuclear import of influenza virus RNA polymerase subunits. J Virol 2006; 81:1339-49. [PMID: 17121807 PMCID: PMC1797515 DOI: 10.1128/jvi.01917-06] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription and replication of the influenza virus RNA genome occur in the nuclei of infected cells through the viral RNA-dependent RNA polymerase consisting of PB1, PB2, and PA. We previously identified a host factor designated RAF-1 (RNA polymerase activating factor 1) that stimulates viral RNA synthesis. RAF-1 is found to be identical to Hsp90. Here, we examined the intracellular localization of Hsp90 and viral RNA polymerase subunits and their molecular interaction. Hsp90 was found to interact with PB2 and PB1, and it was relocalized to the nucleus upon viral infection. We found that the nuclear transport of Hsp90 occurs in cells expressing PB2 alone. The nuclear transport of Hsp90 was in parallel with that of the viral RNA polymerase binary complexes, either PB1 and PB2 or PB1 and PA, as well as with that of PB2 alone. Hsp90 also interacted with the binary RNA polymerase complex PB1-PB2, and it was dissociated from the PB1-PB2 complex upon its association with PA. Furthermore, Hsp90 could form a stable PB1-PB2-Hsp90 complex prior to the formation of a ternary polymerase complex by the assembly of PA in the infected cells. These results suggest that Hsp90 is involved in the assembly and nuclear transport of viral RNA polymerase subunits, possibly as a molecular chaperone for the polymerase subunits prior to the formation of a mature ternary polymerase complex.
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Affiliation(s)
- Tadasuke Naito
- Department of Infection Biology, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan
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21
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Deng T, Engelhardt OG, Thomas B, Akoulitchev AV, Brownlee GG, Fodor E. Role of ran binding protein 5 in nuclear import and assembly of the influenza virus RNA polymerase complex. J Virol 2006; 80:11911-9. [PMID: 17005651 PMCID: PMC1676300 DOI: 10.1128/jvi.01565-06] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The influenza A virus RNA-dependent RNA polymerase is a heterotrimeric complex of polymerase basic protein 1 (PB1), PB2, and polymerase acidic protein (PA) subunits. It performs transcription and replication of the viral RNA genome in the nucleus of infected cells. We have identified a nuclear import factor, Ran binding protein 5 (RanBP5), also known as karyopherin beta3, importin beta3, or importin 5, as an interactor of the PB1 subunit. RanBP5 interacted with either PB1 alone or with a PB1-PA dimer but not with a PB1-PB2 dimer or the trimeric complex. The interaction between RanBP5 and PB1-PA was disrupted by RanGTP in vitro, allowing PB2 to bind to the PB1-PA dimer to form a functional trimeric RNA polymerase complex. We propose a model in which RanBP5 acts as an import factor for the newly synthesized polymerase by targeting the PB1-PA dimer to the nucleus. In agreement with this model, small interfering RNA (siRNA)-mediated knock-down of RanBP5 inhibited the nuclear accumulation of the PB1-PA dimer. Moreover, siRNA knock-down of RanBP5 resulted in the delayed accumulation of viral RNAs in infected cells, confirming that RanBP5 plays a biological role during the influenza virus life cycle.
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Affiliation(s)
- Tao Deng
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
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22
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Garaigorta U, Falcón AM, Ortín J. Genetic analysis of influenza virus NS1 gene: a temperature-sensitive mutant shows defective formation of virus particles. J Virol 2006; 79:15246-57. [PMID: 16306596 PMCID: PMC1316024 DOI: 10.1128/jvi.79.24.15246-15257.2005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To perform a genetic analysis of the influenza A virus NS1 gene, a library of NS1 mutants was generated by PCR-mediated mutagenesis. A collection of mutant ribonucleic proteins containing the nonstructural genes was generated from the library that were rescued for an infectious virus mutant library by a novel RNP competition virus rescue procedure. Several temperature-sensitive (ts) mutant viruses were obtained by screening of the mutant library, and the sequences of their NS1 genes were determined. Most of the mutations identified led to amino acid exchanges and concentrated in the N-terminal region of the protein, but some of them occurred in the C-terminal region. Mutant 11C contained three mutations that led to amino acid exchanges, V18A, R44K, and S195P, all of which were required for the ts phenotype, and was characterized further. Several steps in the infection were slightly altered: (i) M1, M2, NS1, and neuraminidase (NA) accumulations were reduced and (ii) NS1 protein was retained in the nucleus in a temperature-independent manner, but these modifications could not justify the strong virus titer reduction at restrictive temperature. The most dramatic phenotype was the almost complete absence of virus particles in the culture medium, in spite of normal accumulation and nucleocytoplasmic export of virus RNPs. The function affected in the 11C mutant was required late in the infection, as documented by shift-up and shift-down experiments. The defect in virion production was not due to reduced NA expression, as virus yield could not be rescued by exogenous neuraminidase treatment. All together, the analysis of 11C mutant phenotype may indicate a role for NS1 protein in a late event in virus morphogenesis.
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Affiliation(s)
- Urtzi Garaigorta
- Centro Nacional de Biotecnología (CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain
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23
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Fodor E, Smith M. The PA subunit is required for efficient nuclear accumulation of the PB1 subunit of the influenza A virus RNA polymerase complex. J Virol 2004; 78:9144-53. [PMID: 15308710 PMCID: PMC506948 DOI: 10.1128/jvi.78.17.9144-9153.2004] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The RNA genome of influenza virus is transcribed and replicated by the viral RNA polymerase complex in the cell nucleus. We have generated green fluorescent protein (GFP)-tagged polymerase subunits to study the assembly of the polymerase complex. Our results show that individually expressed polymerase basic protein 1 (PB1) and polymerase acidic protein (PA) subunits were distributed in both the cytoplasm and the nucleus, while the polymerase basic protein 2 (PB2) subunit accumulated in the nucleus. Although it has been reported that PB1 alone accumulates in the nucleus, we demonstrate that PB1 requires the coexpression of PA for efficient nuclear accumulation. Our results support a model which proposes that PB1 and PA are transported into the nucleus as a complex.
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Affiliation(s)
- Ervin Fodor
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
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24
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Falcón AM, Marión RM, Zürcher T, Gómez P, Portela A, Nieto A, Ortín J. Defective RNA replication and late gene expression in temperature-sensitive influenza viruses expressing deleted forms of the NS1 protein. J Virol 2004; 78:3880-8. [PMID: 15047804 PMCID: PMC374278 DOI: 10.1128/jvi.78.8.3880-3888.2004] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Influenza A virus mutants expressing C-terminally deleted forms of the NS1 protein (NS1-81 and NS1-110) were generated by plasmid rescue. These viruses were temperature sensitive and showed a small plaque size at the permissive temperature. The accumulation of virion RNA in mutant virus-infected cells was reduced at the restrictive temperature, while the accumulation of cRNA or mRNA was not affected, indicating that the NS1 protein is involved in the control of transcription versus replication processes in the infection. The synthesis and accumulation of late virus proteins were reduced in NS1-81 mutant-infected cells at the permissive temperature and were essentially abolished for both viruses at the restrictive temperature, while synthesis and accumulation of nucleoprotein (NP) were unaffected. Probably as a consequence, the nucleocytoplasmic export of virus NP was strongly inhibited at the restrictive temperature. These results indicate that the NS1 protein is essential for nuclear and cytoplasmic steps during the virus cycle.
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Affiliation(s)
- Ana M Falcón
- Centro Nacional de Biotecnología, CSIC, 28049 Madrid, Spain
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25
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Burgui I, Aragón T, Ortín J, Nieto A. PABP1 and eIF4GI associate with influenza virus NS1 protein in viral mRNA translation initiation complexes. J Gen Virol 2004; 84:3263-3274. [PMID: 14645908 DOI: 10.1099/vir.0.19487-0] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
It has previously been shown that influenza virus NS1 protein enhances the translation of viral but not cellular mRNAs. This enhancement occurs by increasing the rate of translation initiation and requires the 5'UTR sequence, common to all viral mRNAs. In agreement with these findings, we show here that viral mRNAs, but not cellular mRNAs, are associated with NS1 during virus infection. We have previously reported that NS1 interacts with the translation initiation factor eIF4GI, next to its poly(A)-binding protein 1 (PABP1)-interacting domain and that NS1 and eIF4GI are associated in influenza virus-infected cells. Here we show that NS1, although capable of binding poly(A), does not compete with PABP1 for association with eIF4GI and, furthermore, that NS1 and PABP1 interact both in vivo and in vitro in an RNA-independent manner. The interaction maps between residues 365 and 535 in PABP1 and between residues 1 and 81 in NS1. These mapping studies, together with those previously reported for NS1-eIF4GI and PABP1-eIF4GI interactions, imply that the binding of all three proteins would be compatible. Collectively, these and previously published data suggest that NS1 interactions with eIF4GI and PABP1, as well as with viral mRNAs, could promote the specific recruitment of 43S complexes to the viral mRNAs.
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Affiliation(s)
- Idoia Burgui
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Tomás Aragón
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Juan Ortín
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Amelia Nieto
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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26
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Huarte M, Falcón A, Nakaya Y, Ortín J, García-Sastre A, Nieto A. Threonine 157 of influenza virus PA polymerase subunit modulates RNA replication in infectious viruses. J Virol 2003; 77:6007-13. [PMID: 12719592 PMCID: PMC154019 DOI: 10.1128/jvi.77.10.6007-6013.2003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous results have shown a correlation between the decrease in protease activity of several influenza A virus PA protein mutants and the capacity to replicate of the corresponding mutant ribonucleoproteins (RNPs) reconstituted in vivo. In this work we studied the phenotype of mutant viruses containing these mutations. Viruses with a T162A mutation, which showed a very moderate decrease both in protease and replication activities of reconstituted RNPs, showed a wild-type phenotype. Viruses with a T157A mutation, which presented a severe decrease in protease activity and replication of RNPs, showed a complex phenotype: (i) transport to the nucleus of PAT157A protein was delayed, (ii) virus multiplication was reduced at both low and high multiplicities, (iii) transcriptive synthesis was unaltered while replicative synthesis, especially cRNA, was diminished, and (iv) viral pathogenesis in mice was reduced, as measured by loss of body weight and virus titers in lungs. Finally, recombinant viruses with a T157E mutation in PA protein, which resulted in a drastic reduction of protease and replication activities of RNPs, were not viable. These results indicate that residue T157 in PA protein is important for the capacity of viral polymerase to synthesize cRNA.
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Affiliation(s)
- Maite Huarte
- Centro Nacional de Biotecnología, Cantoblanco, 28049 Madrid, Spain
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27
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Snow M, Ritchie R, Arnaud O, Villoing S, Aspehaug V, Cunningham CO. Isolation and characterisation of segment 1 of the infectious salmon anaemia virus genome. Virus Res 2003; 92:99-105. [PMID: 12606081 DOI: 10.1016/s0168-1702(02)00322-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The isolation and characterisation of the largest genomic segment of infectious salmon anaemia virus (ISAV) is reported. Following identification of ISAV-specific clones from a cDNA library, a rapid amplification of cDNA ends-PCR strategy was designed to obtain the sequence of the full length mRNA transcript. The full length open reading frame (ORF) of this gene was shown to be 2169 nucleotides in length, encoding a putative protein of 722 aa. This sequence was demonstrated by RT-PCR to be specific to ISAV-infected cell cultures. The start codon of this ORF was preceded by the ISAV consensus sequence 5' GCTAAGA 3' indicating the full 5' end of the gene to have been obtained. Based on protein size and amino acid composition, this protein was shown to be similar to the PB2 protein of other orthomyxoviruses. Furthermore, a bipartite nuclear localisation signal was identified in the C-terminus of the protein as is found on all of the influenza virus P proteins. Expression of the putative PB2 as a green fluorescent marker protein-fusion protein confirmed that this protein exhibited nuclear localisation in a fish cell line. Sequences of the ISAV segment 1 gene were obtained from Scottish, Norwegian and Canadian ISAV isolates. Analyses confirmed the close genetic relationship between Norwegian and Scottish ISAV and indicated that this segment was among the most conserved of the ISAV genes identified to date. Thus, this evidence strongly suggests that the genomic segment 1 of ISAV encodes a polymerase protein which is thought to be analagous in function to the PB2 protein of influenza viruses.
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Affiliation(s)
- M Snow
- FRS Marine Laboratory, PO Box 101, Victoria Road, Aberdeen AB11 9DB, Scotland, UK
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28
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Abstract
Peptide dendrimers are radial or wedge-like branched macromolecules consisting of a peptidyl branching core and/or covalently attached surface functional units. The multimeric nature of these constructs, the unambiguous composition and ease of production make this type of dendrimer well suited to various biotechnological and biochemical applications. Applications include use as biomedical diagnostic reagents, protein mimetics, anticancer and antiviral agents, vaccines and drug and gene delivery vehicles. This review focuses on the different types of peptide dendrimers currently in use and the synthetic methods commonly employed to generate peptide dendrimers ranging from stepwise solid-phase synthesis to chemoselective and orthogonal ligation.
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Affiliation(s)
- Kristen Sadler
- Department of Microbiology and Immunology, Vanderbilt University, Nashville, TN 37232, USA
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29
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Influenza virus replication. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0168-7069(02)07002-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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30
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Aragón T, de la Luna S, Novoa I, Carrasco L, Ortín J, Nieto A. Eukaryotic translation initiation factor 4GI is a cellular target for NS1 protein, a translational activator of influenza virus. Mol Cell Biol 2000; 20:6259-68. [PMID: 10938102 PMCID: PMC86100 DOI: 10.1128/mcb.20.17.6259-6268.2000] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Influenza virus NS1 protein is an RNA-binding protein whose expression alters several posttranscriptional regulatory processes, like polyadenylation, splicing, and nucleocytoplasmic transport of cellular mRNAs. In addition, NS1 protein enhances the translational rate of viral, but not cellular, mRNAs. To characterize this effect, we looked for targets of NS1 influenza virus protein among cellular translation factors. We found that NS1 coimmunoprecipitates with eukaryotic initiation factor 4GI (eIF4GI), the large subunit of the cap-binding complex eIF4F, either in influenza virus-infected cells or in cells transfected with NS1 cDNA. Affinity chromatography studies using a purified His-NS1 protein-containing matrix showed that the fusion protein pulls down endogenous eIF4GI from COS-1 cells and labeled eIF4GI translated in vitro, but not the eIF4E subunit of the eIF4F factor. Similar in vitro binding experiments with eIF4GI deletion mutants indicated that the NS1-binding domain of eIF4GI is located between residues 157 and 550, in a region where no other component of the translational machinery is known to interact. Moreover, using overlay assays and pull-down experiments, we showed that NS1 and eIF4GI proteins interact directly, in an RNA-independent manner. Mapping of the eIF4GI-binding domain in the NS1 protein indicated that the first 113 N-terminal amino acids of the protein, but not the first 81, are sufficient to bind eIF4GI. The first of these mutants has been previously shown to act as a translational enhancer, while the second is defective in this activity. Collectively, these and previously published data suggest a model where NS1 recruits eIF4GI specifically to the 5' untranslated region (5' UTR) of the viral mRNA, allowing for the preferential translation of the influenza virus messengers.
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Affiliation(s)
- T Aragón
- Centro Nacional de Biotecnología (CSIC), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
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31
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Falcón AM, Fortes P, Marión RM, Beloso A, Ortín J. Interaction of influenza virus NS1 protein and the human homologue of Staufen in vivo and in vitro. Nucleic Acids Res 1999; 27:2241-7. [PMID: 10325410 PMCID: PMC148787 DOI: 10.1093/nar/27.11.2241] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A screening for human proteins capable of interacting with influenza virus NS1 has been carried out using the two-hybrid genetic trap in yeast. A cDNA corresponding to the human homologue of Drosophila melanogaster Staufen protein (hStaufen) was isolated that fulfilled all genetic controls of the two-hybrid protocol. Using a hStaufen cDNA isolated from a lambda human library, the interaction of hStaufen and NS1 proteins was characterised in vivo and in vitro. Co-transfection of NS1 cDNA and a partial cDNA of hStaufen led to the relocalisation of recombinant hStaufen protein from its normal accumulation site in the cytoplasm to the nuclear location of NS1 protein. NS1 and hStaufen proteins could be co-immunoprecipitated from extracts of co-transfected cells and from mixtures of extracts containing either protein, as well as from extracts of influenza virus-infected cells. Furthermore, both proteins co-localised in the ribosomal and polysomal fractions of influenza virus-infected cells. The interaction was also detected in pull-down experiments using a resin containing purified hStaufen and NS1 protein translated in vitro. Deletion mapping of the NS1 gene indicated that a mutant protein containing the N-terminal 81 amino acids is unable to interact with hStaufen, in spite of retaining full RNA-binding capacity. These results are discussed in relation to the possible mechanisms of action of hStaufen and its relevance for influenza virus infection.
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Affiliation(s)
- A M Falcón
- Centro Nacional de Biotecnología (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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32
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Pérez M, Avila J. The expression of casein kinase 2alpha' and phosphatase 2A activity. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1449:150-6. [PMID: 10082973 DOI: 10.1016/s0167-4889(99)00008-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Protein phosphatase 2A (PP2A) activity may be differentially regulated by the expression of proteins containing a related amino acid sequence motif such as the casein kinase 2alpha (CK2alpha) subunit or SV40 small t antigen (SVt). Expression of CK2alpha increases PP2A activity whereas SVt decreases its activity. In this work we have tested for the effect of the expression of a third protein containing a similar motif that could be involved in PP2A regulation, the catalytic casein kinase 2alpha' subunit. Our results show that despite the structural similarity of this protein with the other CK2 catalytic (alpha) subunit, the function of the two subunits with respect to the modulation of PP2A activity is quite different: CK2alpha increases whereas CK2alpha' slightly decreases PP2A activity.
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Affiliation(s)
- M Pérez
- Centro de Biología Molecular, Universidad Autónoma de Madrid, 28049-, Madrid, Spain
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Marión RM, Aragón T, Beloso A, Nieto A, Ortín J. The N-terminal half of the influenza virus NS1 protein is sufficient for nuclear retention of mRNA and enhancement of viral mRNA translation. Nucleic Acids Res 1997; 25:4271-7. [PMID: 9336457 PMCID: PMC147036 DOI: 10.1093/nar/25.21.4271] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A collection of C-terminal deletion mutants of the influenza A virus NS1 gene has been used to define the regions of the NS1 protein involved in its functionality. Immunofluorescence analyses showed that the NS1 protein sequences downstream from position 81 are not required for nuclear transport. The capacity of these mutants to bind RNA was studied by in vitro binding tests using a model vRNA probe. These experiments showed that the N-terminal 81 amino acids of NS1 protein are sufficient for RNA binding activity. The collection of mutants also served to map the NS1 sequences required for nuclear retention of mRNA and for stimulation of viral mRNA translation, using the NP gene as reporter. The results obtained indicated that the N-terminal 113 amino acids of NS1 protein are sufficient for nuclear retention of mRNA and stimulation of viral mRNA translation. The possibility that this region of the protein may be sufficient for virus viability is discussed in relation to the sequences of NS1 genes of field isolates and to the phenotype of known viral mutants affected in the NS1 gene.
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Affiliation(s)
- R M Marión
- Centro Nacional de Biotecnología (CSIC), Cantoblanco, 28049 Madrid, Spain
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34
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Perales B, Ortín J. The influenza A virus PB2 polymerase subunit is required for the replication of viral RNA. J Virol 1997; 71:1381-5. [PMID: 8995663 PMCID: PMC191194 DOI: 10.1128/jvi.71.2.1381-1385.1997] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The transcription and replication of influenza virus RNA (vRNA) were reconstituted in vivo. The experimental approach involved the transfection of plasmids encoding the viral subunits of the polymerase and the nucleoprotein into cells infected with a vaccinia virus recombinant virus expressing the T7 RNA polymerase. As templates, one of two model RNAs was transfected: vNSZ or cNSZ RNA. The RNAs were 240 nucleotides in length, contained the terminal sequences of the NS viral segment, and were of negative or positive polarity, respectively. The accumulation of cRNA and mRNA in cells transfected with vNSZ RNA and the accumulation of vRNA and mRNA in cells transfected with cNSZ RNA were determined by RNase protection assays with labeled vNSZ-L or cNSZ-L probes. The patterns of protected bands obtained indicated that both cRNA replication intermediate and mRNA accumulated when the system was reconstituted with vNSZ RNA. Likewise, both vRNA and mRNA accumulated after reconstitution with cNSZ RNA. The reconstitution of incomplete systems in which any of the subunits of the polymerase or the model RNA were omitted was completely negative for the accumulation of cRNA or vRNA, indicating that the presence of the PB2 subunit in the polymerase is required for replication of vRNA.
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Affiliation(s)
- B Perales
- Centro Nacional de Biotecnologia (CSIC), Madrid, Spain
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35
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Biswas SK, Nayak DP. Influenza virus polymerase basic protein 1 interacts with influenza virus polymerase basic protein 2 at multiple sites. J Virol 1996; 70:6716-22. [PMID: 8794308 PMCID: PMC190714 DOI: 10.1128/jvi.70.10.6716-6722.1996] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Three polymerase proteins of influenza type A virus interact with each other to form the active polymerase complex. Polymerase basic protein 1 (PB1) can interact with PB2 in the presence or absence of polymerase acidic protein. In this study, we investigated the domains of PB1 involved in complex formation with PB2 in vivo, using coexpression and coimmunoprecipitation of the PB1-PB2 complex with monospecific antibodies. Results show that PB1 possesses at least two regions which can interact independently and form stable complexes with PB2. Both of these regions are located at the NH2 terminus of PB1; the COOH-terminal half of PB1 is not involved in interacting with PB2. Deletion analysis further demonstrated that the interacting regions of PB1 encompass amino acids (aa) 48 to 145 and aa 251 to 321. Linker insertions throughout the PB1 sequences did not affect complex formation with PB2. Deletion and linker-insertion mutants of PB1 were tested for polymerase activity in vivo. For this analysis, we developed a simplified assay for viral polymerase activity that uses a reporter chloramphenicol acetyltransferase gene containing the 5' and 3' ends of influenza viral promoter and nontranslating regions (minus sense) of the NS gene joined to a hepatitis delta virus ribozyme at its 3' end. This assay demonstrated that all deletion mutants of PB1 exhibited either background or greatly reduced polymerase activity irrespective of the ability to interact with PB2 and that all linker-insertion mutants except one at the extreme COOH end (L-746) of PB1 were also negative for viral polymerase activity. These results show that compared with complex formation of PB1 with PB2, the polymerase activity of PB1 was extremely sensitive to structural perturbation.
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Affiliation(s)
- S K Biswas
- Department of Microbiology and Immunology and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, California 90024-1747, USA
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36
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Goodrum FD, Shenk T, Ornelles DA. Adenovirus early region 4 34-kilodalton protein directs the nuclear localization of the early region 1B 55-kilodalton protein in primate cells. J Virol 1996; 70:6323-35. [PMID: 8709260 PMCID: PMC190658 DOI: 10.1128/jvi.70.9.6323-6335.1996] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The localization of the adenovirus type 5 34-kDa E4 and 55-kDa E1B proteins was determined in the absence of other adenovirus proteins. When expressed by transfection in human, monkey, hamster, rat, and mouse cell lines, the E1B protein was predominantly cytoplasmic and typically was excluded from the nucleus. When expressed by transfection, the E4 protein accumulated in the nucleus. Strikingly, when coexpressed by transfection in human, monkey, or baby hamster kidney cells, the E1B protein colocalized in the nucleus with the E4 protein. A complex of the E4 and E1B proteins was identified by coimmunoprecipitation in transfected HeLa cells. By contrast to the interaction observed in primate and baby hamster kidney cells, the E4 protein failed to direct the E1B protein to the nucleus in rat and mouse cell lines as well as CHO and V79 hamster cell lines. This failure of the E4 protein to direct the nuclear localization of the E1B protein in REF-52 rat cells was overcome by fusion with HeLa cells. Within 4 h of heterokaryon formation and with protein synthesis inhibited, a portion of the E4 protein present in the REF-52 nuclei migrated to the HeLa nuclei. Simultaneously, the previously cytoplasmic E1B protein colocalized with the E4 protein in both human and rat cell nuclei. These results suggest that a primate cell-specific factor mediates the functional interaction of the E1B and E4 proteins of adenovirus.
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Affiliation(s)
- F D Goodrum
- Molecular Genetics Program, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1064, USA
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37
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Perales B, de la Luna S, Palacios I, Ortín J. Mutational analysis identifies functional domains in the influenza A virus PB2 polymerase subunit. J Virol 1996; 70:1678-86. [PMID: 8627688 PMCID: PMC189991 DOI: 10.1128/jvi.70.3.1678-1686.1996] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A collection of influenza virus PB2 mutant genes was prepared, including N-terminal deletions, C-terminal deletions, and single-amino-acid insertions. These mutant genes, driven by a T7 promoter, were expressed by transfection into COS-1 cells infected with a vaccinia virus encoding T7 RNA polymerase. Mutant proteins accumulated to levels similar to that of wild-type PB2. Immunofluorescence analyses showed that the C-terminal region of the protein is essential for nuclear transport and that internal sequences affect nuclear localization, confirming previous results (J. Mukaijawa and D. P. Nayak, J. Virol. 65:245-253, 1991). The biological activity of these mutants was tested by determining their capacity to (i) reconstitute RNA polymerase activity in vivo by cotransfection with proteins NP, PB1, and PA and a virion-like RNA encoding the cat gene into vaccinia virus T7-infected COS-1 cells and (ii) complete with the wild-type PB2 activity. In addition, when tested at different temperatures in vivo, two mutant PB2 proteins showed a temperature-sensitive phenotype. The lack of interference shown by some N-terminal deletion mutants and the complete interference obtained with a C-terminal deletion mutant encoding only 124 amino acids indicated that this protein domain is responsible for interaction with another component of the polymerase, probably PB1. To further characterize the mutants, their ability to induce in vitro synthesis of viral cRNA or mRNA was tested by using ApG or beta-globin mRNA as a primer. One of the mutants, 1299, containing an isoleucine insertion at position 299, was able to induce cRNA and mRNA synthesis in ApG-primed reactions but required a higher beta-globin mRNA concentration than wild-type PB2 for detection of in vitro synthesis. This result suggested that mutant I299 has diminished cap-binding activity.
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Affiliation(s)
- B Perales
- Centro Nacional de Biotecnología (CSIC), Madrid, Spain
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38
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Sanz-Ezquerro JJ, Zürcher T, de la Luna S, Ortín J, Nieto A. The amino-terminal one-third of the influenza virus PA protein is responsible for the induction of proteolysis. J Virol 1996; 70:1905-11. [PMID: 8627716 PMCID: PMC190019 DOI: 10.1128/jvi.70.3.1905-1911.1996] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have previously described the fact that the individual expression of influenza virus PA protein induced a generalized proteolysis (J.J. Sanz-Ezquerro, S. de la Luna, Ortin, and A. Nieto, J. Virol. 69:2420-2426, 1995). In this study, we have further characterized this effect by mapping the regions of PA protein required and have found by deletion analysis that the first 247 amino acids are sufficient to bring about this activity. PA mutants that were able to decrease the accumulation levels of coexpressed proteins also presented lower steady-state levels due to a reduction in their half-lives. Furthermore, the PA wild type produced a decrease in the stationary levels of different PA versions, indicating that is itself a target for its induced proteolytic process. All of the PA proteins that induced proteolysis presented nuclear localization, being the sequences responsible for nuclear transport located inside the first 247 amino acids of the molecule. To distinguish between the regions involved in nuclear localization and those involved in induction of proteolysis, we fused the nuclear localization signal of the simian virus 40 T antigen to the carboxy terminus of the cytosolic versions of PA. None of the cytosolic PA versions affected in the first 247-amino-acid part of PA, which were now located in the nucleus, were able to induce proteolysis, suggesting that conservation of a particular conformation in this region of the molecule is required for the effect observed. The fact that all of the PA proteins able to induce proteolysis presented nuclear localization, together with the observation that this activity is shared by influenza virus PA proteins from two different type A viruses, suggests a physiological role for this PA protein activity in viral infection.
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Pérez DR, Donis RO. A 48-amino-acid region of influenza A virus PB1 protein is sufficient for complex formation with PA. J Virol 1995; 69:6932-9. [PMID: 7474111 PMCID: PMC189611 DOI: 10.1128/jvi.69.11.6932-6939.1995] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The concerted activity of four influenza virus proteins, PB1, PB2, PA, and NP is necessary and sufficient for transcription and replication of the viral genome in the nucleus of the cell. The three P proteins form a heterotrimeric complex in virions and the nuclei of infected cells. Biochemical analyses have shown specific interactions between PB1 and PA as well as PB1 and PB2, indicating that PB1 is the backbone of the complex. To identify domains of PB1 involved in binding PA, a two-hybrid system adapted for mammalian cells (CV-1) was implemented. First, we demonstrate the ability of PB1 and PA to interact efficiently and specifically in reciprocal combinations of two-hybrid reporter moieties, suggesting that transcription factor module fusion did not interfere sterically or allosterically with interaction between PB1 and PA. Subsequent analyses with a set of chimeric proteins with truncations of the PB1 C termini, N termini, or internal sequences led to the identification of a region at the N terminus of PB1 responsible for binding PA. Forty-eight amino acids at the N terminus of PB1 were sufficient for binding PA in vivo with the same efficiency as the complete PB1 protein. This region of PB1 responsible for binding PA does not overlap with other previously described PB1 functional domains involved in nuclear transport and RNA polymerization. We propose to name this region of interaction with PA domain alpha, to differentiate it from other functional domains described for PB1.
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Affiliation(s)
- D R Pérez
- Department of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln 68583, USA
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Ochoa M, Bárcena J, de la Luna S, Melero JA, Douglas AR, Nieto A, Ortín J, Skehel JJ, Portela A. Epitope mapping of cross-reactive monoclonal antibodies specific for the influenza A virus PA and PB2 polypeptides. Virus Res 1995; 37:305-15. [PMID: 8533465 DOI: 10.1016/0168-1702(95)00039-s] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Characterization of the epitopes recognized by 21 monoclonal antibodies (MAbs) specific for the influenza A virus PA (13 MAbs) and PB2 (8 MAbs) polypeptides (Bárcena et al. (1994) J. Virol. 68, 6900-6909) raised against denatured polypeptides produced in E. coli is described. MAbs were characterized by: (1) competitive binding ELISAs; (2) mapping of the protein regions that specify their binding sites; and (3) analyses of their ability to recognize the corresponding viral protein in a number of viral isolates. Five and three non-overlapping antigenic areas were defined by the anti-PA and anti-PB2 MAbs, respectively. Five of the anti-PA MAbs recognized antigenic determinants located within the amino-terminal 157 amino acids of the PA protein, and 6 others reacted strongly with a PA fragment comprising the first 236 amino acids. All 8 anti-PB2 antibodies reacted strongly with a polypeptide fragment containing amino acids 1-113 of the PB2 protein. Analyses of the reactivities of 4 anti-P antibodies with 23 influenza A virus reference strains isolated over a period of 61 years and recovered from humans, pigs, birds and horses, showed that the epitopes were conserved among all viral isolates. The application of these antibodies as research and diagnostic tools is discussed.
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Affiliation(s)
- M Ochoa
- Instituto de Salud Carlos III, Centro Nacional de Biología Celular y Retrovirus, Madrid, Spain
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Sanz-Ezquerro JJ, de la Luna S, Ortín J, Nieto A. Individual expression of influenza virus PA protein induces degradation of coexpressed proteins. J Virol 1995; 69:2420-6. [PMID: 7884889 PMCID: PMC188916 DOI: 10.1128/jvi.69.4.2420-2426.1995] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In the process of in vivo reconstitution of influenza virus transcriptase-replicase complex, an inhibitory effect was observed when the level of PA protein expression was increased. This inhibition was paralleled by a decrease in the accumulation of the other influenza virus core proteins. The sole expression of PA protein was sufficient to reduce the accumulation level of the proteins encoded by the coexpressed genes. The PA effect was observed upon influenza virus and non-influenza virus proteins and independently of the expression system chosen and the origin of cell line used. The expression of PA protein did not induce variations in the translation of the target proteins but did induce variations on their half-lives, which were clearly reduced. A functional PA subunit seems to be necessary to induce this negative effect, because an inactive point mutant was unable to decrease the steady-state levels or the half-lives of the reporter proteins. The PA effect was observed as early as 5 h after its expression, and continuous synthesis of proteins was not required for performance of its biological activity. The results presented represent the first biological activity of individually expressed PA polymerase subunit.
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Affiliation(s)
- J J Sanz-Ezquerro
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco
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42
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[21] Systems to express recombinant RNA molecules by the influenza A virus polymerase in vivo. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1067-2389(06)80053-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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43
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44
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Bárcena J, Ochoa M, de la Luna S, Melero JA, Nieto A, Ortín J, Portela A. Monoclonal antibodies against influenza virus PB2 and NP polypeptides interfere with the initiation step of viral mRNA synthesis in vitro. J Virol 1994; 68:6900-9. [PMID: 7933070 PMCID: PMC237125 DOI: 10.1128/jvi.68.11.6900-6909.1994] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Two panels of monoclonal antibodies (MAbs) specific for the influenza A virus PA and PB2 polypeptides have been obtained from mice immunized with denatured proteins produced in Escherichia coli. All MAbs (13 specific for the PA polypeptide and 8 specific for the PB2 protein) reacted to the corresponding influenza virus protein in Western blotting (immunoblotting), immunoprecipitation, and immunofluorescence assays. To gain information about the roles of the nucleoprotein (NP) and PB2 and PA proteins during viral mRNA synthesis, the 21 anti-P antibodies and 3 anti-NP antibodies (J. A. López, M. Guillen, A. Sánchez-Fauquier, and J. A. Melero, J. Virol. Methods 13:255-264, 1986) were purified and tested for their ability to inhibit the transcriptase activity associated with viral cores purified from virions. Four of the antibodies (one anti-PB2 and the three anti-NP MAbs) inhibited transcription by more than 50% compared with unrelated control antibodies. The inhibitory effect was not due to a nonspecific effect of the antibody preparations, because these MAbs did not inhibit transcription when tested on influenza B virus nucleocapsids, which are not recognized by the antibodies. To determine whether the antibodies were acting on an early transcription step, transcription reactions were carried out in the presence of globin mRNA (a mixture of alpha- and beta-globin chains) and only one labeled nucleoside triphosphate (either GTP or CTP). The results obtained showed that MAbs to the PB2 and NP polypeptides interfered with the initiation step of mRNA-primed transcription. The implications of these results regarding initiation of viral mRNA synthesis are discussed.
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Affiliation(s)
- J Bárcena
- Centro Nacional de Microbiología Virología e Inmunología Sanitarias, Instituto de Salud Carlos III, Madrid, Spain
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