1
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Fundamental Contribution and Host Range Determination of ANP32A and ANP32B in Influenza A Virus Polymerase Activity. J Virol 2019; 93:JVI.00174-19. [PMID: 30996088 PMCID: PMC6580979 DOI: 10.1128/jvi.00174-19] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/09/2019] [Indexed: 12/14/2022] Open
Abstract
The polymerase of the influenza virus is part of the key machinery necessary for viral replication. However, the avian influenza virus polymerase is restricted in mammalian cells. The cellular protein ANP32A has been recently found to interact with viral polymerase and to influence both polymerase activity and interspecies restriction. We report here that either human ANP32A or ANP32B is indispensable for human influenza A virus RNA replication. The contribution of huANP32B is equal to that of huANP32A, and together they play a fundamental role in the activity of human influenza A virus polymerase, while neither human ANP32A nor ANP32B supports the activity of avian viral polymerase. Interestingly, we found that avian ANP32B was naturally inactive, leaving avian ANP32A alone to support viral replication. Two amino acid mutations at sites 129 to 130 in chicken ANP32B lead to the loss of support of viral replication and weak interaction with the viral polymerase complex, and these amino acids are also crucial in the maintenance of viral polymerase activity in other ANP32 proteins. Our findings strongly support ANP32A and ANP32B as key factors for both virus replication and adaptation.IMPORTANCE The key host factors involved in the influenza A viral polymerase activity and RNA replication remain largely unknown. We provide evidence here that ANP32A and ANP32B from different species are powerful factors in the maintenance of viral polymerase activity. Human ANP32A and ANP32B contribute equally to support human influenza viral RNA replication. However, unlike avian ANP32A, the avian ANP32B is evolutionarily nonfunctional in supporting viral replication because of a mutation at sites 129 and 130. These sites play an important role in ANP32A/ANP32B and viral polymerase interaction and therefore determine viral replication, suggesting a novel interface as a potential target for the development of anti-influenza strategies.
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2
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Momose F, Morikawa Y. Polycistronic Expression of the Influenza A Virus RNA-Dependent RNA Polymerase by Using the Thosea asigna Virus 2A-Like Self-Processing Sequence. Front Microbiol 2016; 7:288. [PMID: 27014212 PMCID: PMC4782009 DOI: 10.3389/fmicb.2016.00288] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 02/23/2016] [Indexed: 01/07/2023] Open
Abstract
The RNA-dependent RNA polymerase (RdRp) of influenza A virus consists of three subunits, PB2, PB1, and PA, and catalyses both viral RNA genome replication and transcription. Cotransfection of four monocistronic expression vectors for these subunits and nucleoprotein with an expression vector for viral RNA reconstitutes functional viral ribonucleoprotein complex (vRNP). However, the specific activity of reconstituted RdRp is usually very low since the expression level and the ratio of the three subunits by transfection are uncontrollable at single-cell levels. For efficient reconstitution of RdRp and vRNP, their levels need to be at least comparable. We constructed polycistronic expression vectors in which the coding sequences of the three subunits were joined with the 2A-like self-processing sequence of Thosea asigna virus (TaV2A) in various orders. The level of PB1 protein, even when it was placed at the most downstream, was comparable with that expressed from the monocistronic PB1 vector. In contrast, the levels of PB2 and PA were very low, the latter of which was most likely due to proteasomal degradation caused by the TaV2A-derived sequences attached to the amino- and/or carboxyl-terminal ends in this expression system. Interestingly, two of the constructs, in which the PB1 coding sequence was placed at the most upstream, showed much higher reporter activity in a luciferase-based mini-genome assay than that observed by cotransfection of the monocistronic vectors. When the coding sequence of selective antibiotic marker was further placed at the most downstream of the PB1-PA-PB2 open reading frame, stable cells expressing RdRp were easily established, indicating that acquisition of antibiotic resistance assured the expression of upstream RdRp. The addition of an affinity tag to the carboxyl-terminal end of PB2 allowed us to isolate reconstituted vRNP. Taken together, the polycistronic expression system for influenza virus RdRp may be available for functional and structural studies on vRNP.
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Affiliation(s)
- Fumitaka Momose
- Laboratory of Viral Infection II, Kitasato Institute for Life Sciences, Kitasato University Tokyo, Japan
| | - Yuko Morikawa
- Laboratory of Viral Infection II, Kitasato Institute for Life Sciences, Kitasato University Tokyo, Japan
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3
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Sugiyama K, Kawaguchi A, Okuwaki M, Nagata K. pp32 and APRIL are host cell-derived regulators of influenza virus RNA synthesis from cRNA. eLife 2015; 4. [PMID: 26512887 PMCID: PMC4718810 DOI: 10.7554/elife.08939] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 10/20/2015] [Indexed: 12/02/2022] Open
Abstract
Replication of influenza viral genomic RNA (vRNA) is catalyzed by viral RNA-dependent RNA polymerase (vRdRP). Complementary RNA (cRNA) is first copied from vRNA, and progeny vRNAs are then amplified from the cRNA. Although vRdRP and viral RNA are minimal requirements, efficient cell-free replication could not be reproduced using only these viral factors. Using a biochemical complementation assay system, we found a novel activity in the nuclear extracts of uninfected cells, designated IREF-2, that allows robust unprimed vRNA synthesis from a cRNA template. IREF-2 was shown to consist of host-derived proteins, pp32 and APRIL. IREF-2 interacts with a free form of vRdRP and preferentially upregulates vRNA synthesis rather than cRNA synthesis. Knockdown experiments indicated that IREF-2 is involved in in vivo viral replication. On the basis of these results and those of previous studies, a plausible role(s) for IREF-2 during the initiation processes of vRNA replication is discussed. DOI:http://dx.doi.org/10.7554/eLife.08939.001 The influenza or “flu” virus infects millions of people each year, with young children and elderly individuals most vulnerable to infection. The influenza virus stores its genetic material in the form of segments of single-stranded viral RNA. After the virus infects a cell, it replicates this genetic material in a two-part process. First, an enzyme made by the virus – called RNA polymerase – uses the viral genomic RNA as a template to form a “complementary” RNA strand (called cRNA). This cRNA molecule is then itself used as a template to make more viral genomic RNA strands, which can go on to form new viruses. Exactly how viral genomic RNA is made from cRNA is poorly understood, although previous research had suggested that this process may also involve proteins belonging to the invaded host cell. However, these host proteins had not been identified. By mixing virus particles with extracts from uninfected human cells, Sugiyama et al. have now found that two host proteins called pp32 and APRIL help viral genomic RNA to form from a cRNA template. Both of these proteins directly interact with the viral RNA polymerase. Sugiyama et al. then reduced the amounts of pp32 and APRIL in human cells that were infected with the influenza virus. Much less viral genomic RNA – and so fewer new virus particles – formed in these cells than in normal cells. Further work is now needed to understand how the pp32 and APRIL proteins interact with viral RNA polymerase. This could eventually lead to the development of new treatments for influenza. DOI:http://dx.doi.org/10.7554/eLife.08939.002
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Affiliation(s)
- Kenji Sugiyama
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Atsushi Kawaguchi
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Mitsuru Okuwaki
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Kyosuke Nagata
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
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4
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Kumar P, Sweeney TR, Skabkin MA, Skabkina OV, Hellen CUT, Pestova TV. Inhibition of translation by IFIT family members is determined by their ability to interact selectively with the 5'-terminal regions of cap0-, cap1- and 5'ppp- mRNAs. Nucleic Acids Res 2013; 42:3228-45. [PMID: 24371270 PMCID: PMC3950709 DOI: 10.1093/nar/gkt1321] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Ribosomal recruitment of cellular mRNAs depends on binding of eIF4F to the mRNA's 5'-terminal 'cap'. The minimal 'cap0' consists of N7-methylguanosine linked to the first nucleotide via a 5'-5' triphosphate (ppp) bridge. Cap0 is further modified by 2'-O-methylation of the next two riboses, yielding 'cap1' (m7GpppNmN) and 'cap2' (m7GpppNmNm). However, some viral RNAs lack 2'-O-methylation, whereas others contain only ppp- at their 5'-end. Interferon-induced proteins with tetratricopeptide repeats (IFITs) are highly expressed effectors of innate immunity that inhibit viral replication by incompletely understood mechanisms. Here, we investigated the ability of IFIT family members to interact with cap1-, cap0- and 5'ppp- mRNAs and inhibit their translation. IFIT1 and IFIT1B showed very high affinity to cap-proximal regions of cap0-mRNAs (K1/2,app ∼9 to 23 nM). The 2'-O-methylation abrogated IFIT1/mRNA interaction, whereas IFIT1B retained the ability to bind cap1-mRNA, albeit with reduced affinity (K1/2,app ∼450 nM). The 5'-terminal regions of 5'ppp-mRNAs were recognized by IFIT5 (K1/2,app ∼400 nM). The activity of individual IFITs in inhibiting initiation on a specific mRNA was determined by their ability to interact with its 5'-terminal region: IFIT1 and IFIT1B efficiently outcompeted eIF4F and abrogated initiation on cap0-mRNAs, whereas inhibition on cap1- and 5'ppp- mRNAs by IFIT1B and IFIT5 was weaker and required higher protein concentrations.
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Affiliation(s)
- Parimal Kumar
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
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5
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Cianci C, Gerritz SW, Deminie C, Krystal M. Influenza nucleoprotein: promising target for antiviral chemotherapy. Antivir Chem Chemother 2012; 23:77-91. [PMID: 22837443 DOI: 10.3851/imp2235] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2012] [Indexed: 12/25/2022] Open
Abstract
In the search for new anti-influenza agents, the viral polymerase has often been targeted due to the involvement of multiple conserved proteins and their distinct activities. Polymerase associates with each of the eight singled-stranded negative-sense viral RNA segments. These transcriptionally competent segments are coated with multiple copies of nucleoprotein (NP) to form the ribonucleoprotein. NP is an abundant essential protein, possessing operative and structural functions, and participating in genome organization, nuclear trafficking and RNA transcription and replication. This review examines the NP structure and function, and explores NP as an emerging target for anti-influenza drug development, focusing on recently discovered aryl piperazine amide inhibitor chemotypes.
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6
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Sequence in the influenza A virus nucleoprotein required for viral polymerase binding and RNA synthesis. J Virol 2012; 86:7292-7. [PMID: 22532672 DOI: 10.1128/jvi.00014-12] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many proposed mechanisms for influenza A viral RNA synthesis include an interaction of the nucleoprotein (NP) with the viral polymerase. To identify an NP sequence required for this interaction, we used the cryoelectron microscopic structure of an influenza virus miniribonucleoprotein as a guide for choosing promising surface-exposed sequences. We show that three amino acids (R204, W207, and R208) located in a loop at the top of the head domain of NP are required for functional interaction with the viral polymerase. Quantitative reverse transcription-PCR (RT-PCR) measurements of RNAs synthesized in minigenome assays established that each of these NP amino acids is required for viral RNA synthesis. The mutation of these three amino acids does not affect nuclear localization or RNA-binding and oligomerization activities of NP. In vitro binding experiments with purified virus polymerase and NPs established that these three amino acids are required for NP binding to the viral polymerase.
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7
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Influenza A virus-generated small RNAs regulate the switch from transcription to replication. Proc Natl Acad Sci U S A 2010; 107:11525-30. [PMID: 20534471 DOI: 10.1073/pnas.1001984107] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The discovery of regulatory small RNAs continues to reshape paradigms in both molecular biology and virology. Here we describe examples of influenza A virus-derived small viral RNAs (svRNAs). svRNAs are 22-27 nt in length and correspond to the 5' end of each of the viral genomic RNA (vRNA) segments. Expression of svRNA correlates with the accumulation of vRNA and a bias in RNA-dependent RNA polymerase (RdRp) activity from transcription toward genome replication. Synthesis of svRNA requires the RdRp, nucleoprotein and the nuclear export protein NS2. In addition, svRNA is detectable during replication of various influenza A virus subtypes across multiple host species and associates physically with the RdRp. We demonstrate that depletion of svRNA has a minimal impact on mRNA and complementary vRNA (cRNA) but results in a dramatic loss of vRNA in a segment-specific manner. We propose that svRNA triggers the viral switch from transcription to replication through interactions with the viral polymerase machinery. Taken together, the discovery of svRNA redefines the mechanistic switch of influenza virus transcription/replication and provides a potential target for broad-range, anti-influenza virus-based therapeutics.
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8
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Dalton RM, Mullin AE, Amorim MJ, Medcalf E, Tiley LS, Digard P. Temperature sensitive influenza A virus genome replication results from low thermal stability of polymerase-cRNA complexes. Virol J 2006; 3:58. [PMID: 16934156 PMCID: PMC1569369 DOI: 10.1186/1743-422x-3-58] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Accepted: 08/25/2006] [Indexed: 12/27/2022] Open
Abstract
Background The RNA-dependent RNA polymerase of Influenza A virus is a determinant of viral pathogenicity and host range that is responsible for transcribing and replicating the negative sense segmented viral genome (vRNA). Transcription produces capped and polyadenylated mRNAs whereas genome replication involves the synthesis of an alternative plus-sense transcript (cRNA) with unmodified termini that is copied back to vRNA. Viral mRNA transcription predominates at early stages of viral infection, while later, negative sense genome replication is favoured. However, the "switch" that regulates the transition from transcription to replication is poorly understood. Results We show that temperature strongly affects the balance between plus and minus-sense RNA synthesis with high temperature causing a large decrease in vRNA accumulation, a moderate decrease in cRNA levels but (depending on genome segment) either increased or unchanged levels of mRNA. We found no evidence implicating cellular heat shock protein activity in this effect despite the known association of hsp70 and hsp90 with viral polymerase components. Temperature-shift experiments indicated that polymerase synthesised at 41°C maintained transcriptional activity even though genome replication failed. Reduced polymerase association with viral RNA was seen in vivo and in confirmation of this, in vitro binding assays showed that temperature increased the rate of dissociation of polymerase from both positive and negative sense promoters. However, the interaction of polymerase with the cRNA promoter was particularly heat labile, showing rapid dissociation even at 37°C. This suggested that vRNA synthesis fails at elevated temperatures because the polymerase does not bind the promoter. In support of this hypothesis, a mutant cRNA promoter with vRNA-like sequence elements supported vRNA synthesis at higher temperatures than the wild-type promoter. Conclusion The differential stability of negative and positive sense polymerase-promoter complexes explains why high temperature favours transcription over replication and has implications for the control of viral RNA synthesis at physiological temperatures. Furthermore, given the different body temperatures of birds and man, these finding suggest molecular hypotheses for how polymerase function may affect host range.
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Affiliation(s)
- Rosa M Dalton
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Anne E Mullin
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Maria Joao Amorim
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Elizabeth Medcalf
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Laurence S Tiley
- Centre for Veterinary Science, University of Cambridge, Madingley Road, Cambridge CB3 OES, UK
| | - Paul Digard
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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9
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Lee MK, Bae SH, Park CJ, Cheong HK, Cheong C, Choi BS. A single-nucleotide natural variation (U4 to C4) in an influenza A virus promoter exhibits a large structural change: implications for differential viral RNA synthesis by RNA-dependent RNA polymerase. Nucleic Acids Res 2003; 31:1216-23. [PMID: 12582241 PMCID: PMC150232 DOI: 10.1093/nar/gkg214] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Revised: 12/20/2002] [Accepted: 12/20/2002] [Indexed: 11/13/2022] Open
Abstract
The influenza A virus promoter is recognized by the influenza A virus RNA-dependent RNA polymerase, and directs both transcription and replication of the viral RNA genome. Within the sequence of this promoter, flu strains exhibit a natural, unique variation, either a U or a C, at the fourth position from the 3' end. Promoters that contain a C residue (C4 promoter), which are invariably found in genome segments that encode the three RNA polymerase subunits (PB1, PB2 and PA), down-regulate transcription but activate genome replication. Here, we have determined the structure of the C4 promoter by NMR spectroscopy and compared it with the structure of the U4 promoter, which was determined previously. The structure of the internal loop in the C4 promoter is similar to that of the U4 promoter. However, the terminal stem of the C4 promoter is strikingly different from that of the U4 promoter. These structural data suggest that the internal loop is important for polymerase binding to the promoter, and the terminal stem is crucial for differential regulation of transcription and replication.
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Affiliation(s)
- Mi-Kyung Lee
- Department of Chemistry and National Creative Research Initiative Center, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejon 305-701, Korea
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10
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Portela A, Digard P. The influenza virus nucleoprotein: a multifunctional RNA-binding protein pivotal to virus replication. J Gen Virol 2002; 83:723-734. [PMID: 11907320 DOI: 10.1099/0022-1317-83-4-723] [Citation(s) in RCA: 371] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
All viruses with negative-sense RNA genomes encode a single-strand RNA-binding nucleoprotein (NP). The primary function of NP is to encapsidate the virus genome for the purposes of RNA transcription, replication and packaging. The purpose of this review is to illustrate using the influenza virus NP as a well-studied example that the molecule is much more than a structural RNA-binding protein, but also functions as a key adapter molecule between virus and host cell processes. It does so through the ability to interact with a wide variety of viral and cellular macromolecules, including RNA, itself, two subunits of the viral RNA-dependent RNA polymerase and the viral matrix protein. NP also interacts with cellular polypeptides, including actin, components of the nuclear import and export apparatus and a nuclear RNA helicase. The evidence for the existence of each of these activities and their possible roles in transcription, replication and intracellular trafficking of the virus genome is considered.
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Affiliation(s)
- Agustín Portela
- División de Productos Biológicos y Biotecnología, Agencia Española del Medicamento, Majadahonda 28220, Madrid, Spain1
| | - Paul Digard
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK2
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11
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Lee MTM, Bishop K, Medcalf L, Elton D, Digard P, Tiley L. Definition of the minimal viral components required for the initiation of unprimed RNA synthesis by influenza virus RNA polymerase. Nucleic Acids Res 2002; 30:429-38. [PMID: 11788704 PMCID: PMC99831 DOI: 10.1093/nar/30.2.429] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The first 11 nt at the 5' end of influenza virus genomic RNA were shown to be both necessary and sufficient for specific binding by the influenza virus polymerase. A novel in vitro transcription assay, in which the polymerase was bound to paramagnetic beads via a biotinylated 5'-vRNA oligonucleotide, was used to study the activities of different forms of the polymerase. Complexes composed of co-expressed PB1/PB2/PA proteins and a sub-complex composed of PB1/PA bound to the 5'-vRNA oligonucleotide, whereas PB1 expressed alone did not. The enriched 5'-vRNA/PB1/PB2/PA complex was highly active for ApG and globin mRNA primed transcription on a model 3'-vRNA template. RNA synthesis in the absence of added primers produced products with 5'-terminal tri- or diphosphate groups, indicating that genuine unprimed initiation of transcription also occurred. No transcriptase activity was detected for the PB1/PA complex. These results demonstrate a role for PA in the enhancement of 5' end binding activity of PB1, a role for PB2 in the assembly of a polymerase complex able to perform both cap-dependent and -independent synthesis and that NP is not required for the initiation of replicative transcription.
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MESH Headings
- Binding Sites
- Chromatography, Affinity
- DNA-Directed RNA Polymerases/genetics
- DNA-Directed RNA Polymerases/isolation & purification
- DNA-Directed RNA Polymerases/metabolism
- Electrophoretic Mobility Shift Assay
- Enzymes, Immobilized/genetics
- Enzymes, Immobilized/metabolism
- Genome, Viral
- Globins/genetics
- HeLa Cells
- Humans
- Multienzyme Complexes
- Oligoribonucleotides/genetics
- Oligoribonucleotides/metabolism
- Orthomyxoviridae/enzymology
- Orthomyxoviridae/genetics
- Protein Binding
- Protein Subunits
- RNA Probes/genetics
- RNA Probes/metabolism
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- RNA, Viral/biosynthesis
- RNA, Viral/genetics
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/isolation & purification
- RNA-Binding Proteins/metabolism
- RNA-Dependent RNA Polymerase/chemistry
- RNA-Dependent RNA Polymerase/genetics
- RNA-Dependent RNA Polymerase/isolation & purification
- RNA-Dependent RNA Polymerase/metabolism
- Recombinant Proteins/metabolism
- Templates, Genetic
- Transcription, Genetic/genetics
- Viral Proteins/genetics
- Viral Proteins/isolation & purification
- Viral Proteins/metabolism
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Affiliation(s)
- M T Michael Lee
- Centre for Veterinary Science, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
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12
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Abstract
RNA viruses use several initiation strategies to ensure that their RNAs are synthesized in appropriate amounts, have correct termini, and can be translated efficiently. Many viruses with genomes of single-stranded positive-, negative-, and double-stranded RNA initiate RNA synthesis by a de novo (primer-independent) mechanism. This review summarizes biochemical features and variations of de novo initiation in viral RNA replication.
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Affiliation(s)
- C C Kao
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
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13
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Honda A, Mizumoto K, Ishihama A. Identification of the 5' terminal structure of influenza virus genome RNA by a newly developed enzymatic method. Virus Res 1998; 55:199-206. [PMID: 9725672 DOI: 10.1016/s0168-1702(98)00048-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A combination of T4 polynucleotide kinase, Escherichia coli alkaline phosphatase, yeast Saccharomyces cerevisiae capping enzyme consisting of alpha (RNA guanylyltransferase) and beta (RNA 5'-triphosphatase) subunits. and its alpha subunit without RNA 5'-phosphatase activity was used to establish a simple enzymatic method for determination of RNA species with 5'-hydroxyl, 5'-monophosphate, 5'-diphosphate or 5'-triphosphate termini. Using this method, we found that viral genome RNA (vRNA) segments of both A-type and C-type influenza viruses carry tri- or diphosphates at their 5' termini. The conclusion was based on the observations that: (i) 5' phosphorylation of vRNAs by T4 polynucleotide kinase takes place only after phosphatase treatment; and (ii) capping of vRNAs can be observed with both the intact yeast capping enzyme and its alpha subunit alone devoid of RNA 5'-triphosphatase activity; but (iii) the level of capping is higher for the alphabeta holoenzyme than the alpha subunit though the relative level varies depending on RNA preparations. The results support the de novo initiation for the RNA replication although transcription of influenza vRNAs is initiated by host cell capped RNAs as primers.
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Affiliation(s)
- A Honda
- Department of Molecular Genetics, National Institute of Genetics, Mishima, Shizuoka, Japan.
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14
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Abstract
Coronavirus, with a 31-kb RNA genome, replicates its own RNA and transcribes subgenomic mRNAs by complex mechanisms. Viral RNA synthesis is regulated by multiple RNA regions, which appear to interact either directly or indirectly. Multiple cellular proteins bind to these regions and may undergo additional protein-protein interactions. These findings suggest that coronavirus RNA synthesis is carried out on a ribonucleoprotein via a mechanism that involves both viral and cellular proteins associated with viral RNA, similar to DNA-dependent RNA transcription. This mode of RNA synthesis may be applicable to most RNA viruses.
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Affiliation(s)
- M M Lai
- Howard Hughes Medical Institute, Department of Molecular Microbiology and Immunology, University of Southern California School of Medicine, Los Angeles 90033-1054, USA
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15
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Tiley LS, Hagen M, Matthews JT, Krystal M. Sequence-specific binding of the influenza virus RNA polymerase to sequences located at the 5' ends of the viral RNAs. J Virol 1994; 68:5108-16. [PMID: 8035510 PMCID: PMC236454 DOI: 10.1128/jvi.68.8.5108-5116.1994] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The enzymatic activity of recombinant influenza virus RNA polymerase is strictly dependent on the addition of a template RNA containing 5' and 3' viral sequences. Here we report the analysis of the binding specificity and physical characterization of the complex by using gel shift, modification interference, and density gradient techniques. The 13S complex binds specifically to short synthetic RNAs that mimic the partially double stranded panhandle structures found at the termini of both viral RNA and cRNA. The polymerase will also bind independently to the single-stranded 5' or 3' ends of viral RNA. It binds most strongly to specific sequences within the 5' end but is unable to bind these sequences in the context of a completely double stranded structure. Modification interference analysis identified the short sequence motifs at the 5' ends of the viral RNA and cRNA templates that are critical for binding.
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Affiliation(s)
- L S Tiley
- Department of Virology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543
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16
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Hagen M, Chung TD, Butcher JA, Krystal M. Recombinant influenza virus polymerase: requirement of both 5' and 3' viral ends for endonuclease activity. J Virol 1994; 68:1509-15. [PMID: 8107213 PMCID: PMC236607 DOI: 10.1128/jvi.68.3.1509-1515.1994] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Influenza virus polymerase complexes that were expressed in the absence of genomic viral RNA and nucleoprotein were examined for endonuclease activity and transcriptase ability in vitro. Nuclear extracts of cells that express influenza virus polymerase through recombinant vaccinia virus infection did not display specific endonuclease activity in vitro. This polymerase presumably represents an early form of enzyme present in infected cells prior to ribonucleoprotein assembly. Upon addition of a virus-like model RNA template, containing the partially complementary sequence found at the ends of viral RNA, endonuclease activity is stimulated in a concentration-dependent and sequence-specific manner. Once stimulated, the polymerase is able to elongate from the added viral template. Thus, addition of viral template is required for polymerase activity, while the presence of nucleoprotein is not required for limited transcription. Also, full activation of this recombinant viral polymerase is dependent on the presence of both the 3' and 5' ends of the viral genome, as model RNA containing either end alone could not effectively trigger the endonuclease.
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Affiliation(s)
- M Hagen
- Department of Virology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08540
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Seong BL, Brownlee GG. A new method for reconstituting influenza polymerase and RNA in vitro: a study of the promoter elements for cRNA and vRNA synthesis in vitro and viral rescue in vivo. Virology 1992; 186:247-60. [PMID: 1727600 DOI: 10.1016/0042-6822(92)90079-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The influenza RNA polymerase is known to catalyse three distinct copying activities: (i) transcription of minus-sense virion RNA (vRNA) into mRNA, (ii) transcription of vRNA into full-length complementary RNA (cRNA), and (iii) transcription of cRNA to vRNA. Ever since the discovery of the conserved 13 and 12 long sequences at each end of all the influenza RNA segments, these have been good candidates for promoters of transcription. By devising a new, simple method for preparing influenza polymerase complex capable of transcribing in vitro added short model RNA templates without interference from endogenous viral RNA, we have now tested the promoter hypothesis. We conclude that the 13 long and the 12 long 3' conserved sequences of cRNA and vRNA of influenza A virus are by themselves sufficient to promote vRNA and cRNA synthesis in vitro. Using our new method, we also show that chloramphenicol acetyl transferase (CAT) activity can be detected in MDBK (bovine kidney) cells, after transfection of influenza polymerase assembled with a negatively stranded CAT RNA, even in the absence of helper virus. As in a previously described method (Luytjes et al., 1989), CAT activity is amplified by helper virus and can be rescued in infectious recombinant virus.
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Affiliation(s)
- B L Seong
- Sir William Dunn School of Pathology, University of Oxford, United Kingdom
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Shapiro GI, Krug RM. Influenza virus RNA replication in vitro: synthesis of viral template RNAs and virion RNAs in the absence of an added primer. J Virol 1988; 62:2285-90. [PMID: 2453679 PMCID: PMC253375 DOI: 10.1128/jvi.62.7.2285-2290.1988] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The two steps in influenza virus RNA replication are (i) the synthesis of template RNAs, i.e., full-length copies of the virion RNAs, and (ii) the copying of these template RNAs into new virion RNAs. We prepared nuclear extracts from infected HeLa cells that catalyzed both template RNA and virion RNA synthesis in vitro in the absence of an added primer. Antibody depletion experiments implicated nucleocapsid protein molecules not associated with nucleocapsids in template RNA synthesis for antitermination at the polyadenylation site used during viral mRNA synthesis. Experiments with the WSN influenza virus temperature-sensitive mutant ts56 containing a defect in the nucleocapsid protein proved that the nucleocapsid protein was indeed required for template RNA synthesis both in vivo and in vitro. Nuclear extracts prepared from mutant virus-infected cells synthesized template RNA at the permissive temperature but not at the nonpermissive temperature, whereas the synthesis of mRNA-size transcripts was not decreased at the nonpermissive temperature. Antibody depletion experiments showed that nucleocapsid protein molecules not associated with nucleocapsids were also required for the copying of template RNA into virion RNA. In contrast to the situation with the synthesis of transcripts complementary to virion RNA, no discrete termination product(s) were made during virion RNA synthesis in vitro in the absence of nucleocapsid protein molecules.
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Affiliation(s)
- G I Shapiro
- Graduate Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021
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Detjen BM, St Angelo C, Katze MG, Krug RM. The three influenza virus polymerase (P) proteins not associated with viral nucleocapsids in the infected cell are in the form of a complex. J Virol 1987; 61:16-22. [PMID: 3783823 PMCID: PMC255189 DOI: 10.1128/jvi.61.1.16-22.1987] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The three influenza virus polymerase, or P, proteins (PB1, PB2, and PA) that are associated with viral nucleocapsids and are responsible for viral mRNA synthesis are in the form of a complex that moves down the template in association with the growing mRNAs during transcription (J. Braam, I. Ulmanen, and R.M. Krug, Cell 34:609-618, 1983). We determined whether infected cells contained a pool of P proteins not associated with viral nucleocapsids and, if so, whether the P proteins in this pool were in the form of a complex with each other. The cytoplasmic and nuclear extracts from infected cells were depleted of nucleocapsids by centrifugation, and the resulting supernatants were subjected to immunoprecipitation with an antiserum specific for either the PB1 protein or the PB2 protein. Both antisera precipitated all three P proteins, indicating that the P proteins were in a complex that was largely resistant to disruption by the detergents present in the immunoprecipitation buffer. Sucrose density gradient analysis showed that the P protein complexes ranged from about 11S to 22S and that almost all of the PB1 and PB2 protein molecules synthesized during a 1-h period (2.5 to 3.5 h postinfection) were in these complexes. Little or no free PB1 or PB2 protein was detected. The possible role of these nonnucleocapsid P protein complexes in the initiation and reinitiation of virus-specific RNA synthesis is discussed.
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Naeve CW, Summers DF. Electron microscopy of vesicular stomatitis virus replicative ribonucleoproteins. J Virol 1980; 34:764-71. [PMID: 6247510 PMCID: PMC288764 DOI: 10.1128/jvi.34.3.764-771.1980] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The objective of this investigation was to examine by electron microscopy the replicative ribonucleoprotein (RNP) structures synthesized in vesicular stomatitis virus-infected HeLa cells. Pulse-labeled in vivo products of vesicular stomatitis virus replication and transcription can be separated by centrifugation in Renografin gradients. Transcription complexes are dissociated, allowing nascent messenger RNPs to remain at the top of the gradient, whereas RNPs biochemically consistent with replication complexes sediment to the middle of the gradient. Examination of these structures by electron microscopy revealed that all exist as coiled or helical RNPs having dimensions of approximately 20 by 700 nm. These structures can be further subdivided into three major morphological classes: (i) linear forms (20 by 769 +/- 158 nm), which have both ends free; (ii) circular forms (20 by 679 +/- 95 nm), which appear to have both ends joined; and (iii) complex forms, which include those structures which are branched replicative complexes as well as those which are random. To distinguish random complexes and possible transcriptive complex contaminants from replicative complexes, it was necessary to uncoil the RNP structures with EDTA so that length measurements could be made relating the nascent strand length to its position on the template. After EDTA treatment, the linear RNPs uncoiled (10 by 4,035 +/- 3,802 nm), and the circular morphology virtually disappeared. However, a new form appeared which was one-half the length and double the width (20 by 2,103 +/- 306 nm) of full-length RNPs and contained a loop at one end and two free ends at the other (alpha-form RNP). The distribution and length analysis of these structures, plus and minus EDTA, suggest that the alpha-form RNPs arise by EDTA-induced uncoiling of circular forms held together at the ends. Close scrutiny of uncoiled complex RNPs revealed no single-strand RNP templates with single-strand nascents. However, several complexes were observed which appeared to contain alpha-form templates with single-strand nascent RNPs. Length measurements suggest these complexes are neither random nor transcriptive, but are replicative. These experiments suggest that replication may, in part, occur on circular coiled RNP templates.
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Desselberger U, Racaniello VR, Zazra JJ, Palese P. The 3' and 5'-terminal sequences of influenza A, B and C virus RNA segments are highly conserved and show partial inverted complementarity. Gene 1980; 8:315-28. [PMID: 7358274 DOI: 10.1016/0378-1119(80)90007-4] [Citation(s) in RCA: 223] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The 3'- and 5'-terminal nucleotides of the genome segments of an influenza A, B, and C virus were identified by directly sequencing viral RNA using two different sequencing techniques. A high degree of conservation at the 3' ends as well as at the 5' ends was observed among the genome segments of each virus and among the segments of the three different virus types. A uridine-rich region was observed from positions 17 through 22 at the 5' end of each segment. Moreover, the conserved 3' and 5'-terminal sequences showed partial and inverted complementarity. This feature results in very similar sequences at the 3' ends of the plus and minus strand RNAs and may also enable single-strand RNAs of influenza virus to form "panhandle" structures. Inverted complementary repeats may play an important role in initiation of viral RNA replication.
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Plotch SJ, Tomasz J, Krug RM. Absence of detectable capping and methylating enzymes in influenza virions. J Virol 1978; 28:75-83. [PMID: 702657 PMCID: PMC354249 DOI: 10.1128/jvi.28.1.75-83.1978] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In the presence of Mg(2+) and a specific dinucleotide primer (ApG or GpG), the influenza virion transcriptase synthesizes the eight discrete segments of complementary RNA (cRNA) containing polyadenylic acid (Plotch and Krug, J. Virol. 21:24-34, 1977). Virions were examined for their ability to cap and methylate cRNA containing di- or triphosphorylated 5' termini. By using the primers ppApG, pppApG, or ppGpG, viral cRNA was synthesized in vitro with [alpha-(32)P]-GTP and S-[methyl-(3)H]adenosylmethionine as labeled precursors. DEAE-Sephadex chromatography of the RNase T2 digest of the cRNA product demonstrated no (3)H incorporation at all and the absence of a (32)P-labeled cap structure. The 5' terminus of ppApG-primed cRNA could be capped and methylated by enzymes from vaccinia virus, indicating that the two 5'-terminal phosphates derived from the primer were preserved in the product cRNA. The cap structure formed by the vaccinia enzymes and released by RNase T2 digestion as m(7)GpppA(m)pGp was radioactively labeled at its 3'-terminal phosphate only when [alpha-(32)P]CTP was used as the labeled precursor during transcription. This indicates that the 5'-terminal sequence of the cRNA is ppApGpC and that, therefore, ppApG most probably initiates transcription exactly at the 3' GpCpU(OH) terminus of the virion RNA templates. Virions were also tested for their ability to cap and methylate ppApG in the absence of transcription. No such activities were detected, whereas under the same conditions the vaccinia virus enzymes successfully capped and methylated this compound. Consequently, these experiments, together with those reported earlier, have not detected in influenza virions any capping and methylating enzymes active on the 5'-initiated termini of viral cRNA chains synthesized in vitro, whether these termini possess one, two, or three phosphates. Some mechanism for capping and methylation of viral cRNA must, however, exist, because the viral mRNA (cRNA) synthesized in the infected cell contains 5'-terminal methylated cap structures (Krug et al., J. Virol. 20:45-53, 1976). Possible mechanisms are discussed.
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Moss B, Keith JM, Gershowitz A, Ritchey MB, Palese P. Common sequence at the 5' ends of the segmented RNA genomes of influenza A and B viruses. J Virol 1978; 25:312-8. [PMID: 621778 PMCID: PMC353928 DOI: 10.1128/jvi.25.1.312-318.1978] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Guanylyl- and methyltransferases, isolated from purified vaccinia virus, were used to specifically label the 5' ends of the genome RNAs of influenza A and B viruses. All eight segments were labeled with [alpha-(32)P]guanosine 5'-triphosphate or S-adenosyl[methyl-(3)H]methionine to form "cap" structures of the type m(7)G(5')pppN(m)-, of which unmethylated (p)ppN- represents the original 5' end. Further analyses indicated that m(7)G(5')pppA(m), m(7)G(5')pppA(m)pGp, and m(7)G(5')pppA(m)pGpUp were released from total and individual labeled RNA segments by digestion with nuclease P1, RNase T1, and RNase A, respectively. Consequently, the 5'-terminal sequences of most or all individual genome RNAs of influenza A and B viruses were deduced to be (p)ppApGpUp. The presence of identical sequences at the ends of RNA segments of both types of influenza viruses indicates that they have been specifically conserved during evolution.
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Pettersson RF, Flanegan JB, Rose JK, Baltimore D. 5'-Terminal nucleotide sequences of polio virus polyribosomal RNA and virion RNA are identical. Nature 1977; 268:270-2. [PMID: 196211 DOI: 10.1038/268270a0] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Rohde W, Harms E, Scholtissek C. Biochemical studies on influenza viruses. I. Comparative analysis of equine 2 virus and virus N genes and gene products. Virology 1977; 79:393-404. [PMID: 17217 DOI: 10.1016/0042-6822(77)90366-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Krug RM, Morgan MA, Shatkin AJ. Influenza viral mRNA contains internal N6-methyladenosine and 5'-terminal 7-methylguanosine in cap structures. J Virol 1976; 20:45-53. [PMID: 1086370 PMCID: PMC354964 DOI: 10.1128/jvi.20.1.45-53.1976] [Citation(s) in RCA: 212] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Influenza viral complementary RNA (cRNA), i.e., viral mRNA was radioactive when purified from the cytoplasmic fraction of cordycepin-treated canine kidney cells that were incubated with [methyl-3H]methionine during infection. Approximately 55 to 60% of the methyl-3H radioactivity was in internal N6-methyladenosine, a feature distinguishing this mRNA from those viral mRNA's that are known to be synthesized in the cytoplasm. The remaining methyl-3H radioactivity was in 5'-terminal cap structures that consisted of 7-methylguanosine in pyrophosphate linkage to 2'-o-methyladenosine, N6, 2'-O-dimethyladenosine, or 2'-O-methylguanosine. Methylated adenosine was the predominant penultimate nucleoside in caps, suggesting that cRNA synthesis in infected cells initiates preferentially with adenosine at the 5' end. In contrast to cRNA, influenza virion RNA segments extracted from purified virus contained mainly 5'-terminal ppA and no detectable cap structures.
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Sugiura A, Ueda M, Tobita K, Enomoto C. Further isolation and characterization of temperature-sensitive mutants of influenza virus. Virology 1975; 65:363-73. [PMID: 1168970 DOI: 10.1016/0042-6822(75)90042-2] [Citation(s) in RCA: 75] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Keith J, Gleason M, Fraenkel-Conrat H. Characterization of the end groups of RNA of Rous sarcoma virus. Proc Natl Acad Sci U S A 1974; 71:4371-5. [PMID: 4373713 PMCID: PMC433885 DOI: 10.1073/pnas.71.11.4371] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The 3' terminus of the 30-35S RNA of Rous sarcoma virus is adenosine. Its amount indicates an average molecular weight for that RNA of about 3 x 10(6). The 5' terminus of 30-35S RNA of Rous sarcoma virus was not di- or triphosphorylated, whether isolated by the standard procedure or from virus collected within 3 min of its release from the cells.
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Verbert AP, Sergeant A, Krsmanovic V. 5'-TriphosphaTe termini of RNAs made in vivo and in vitro by HeLa and KB cell DNA-dependent RNA polymerases. Biochimie 1974; 56:1103-10. [PMID: 4447808 DOI: 10.1016/s0300-9084(74)80098-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Abstract
The kinetics of radioactive phosphate incorporation into the adenosine and guanosine nucleoside triphosphate termini of bacterial ribonucleic acid (RNA) was studied. Knowledge obtained in a previous investigation of the kinetics of phosphate incorporation into their precursors, adenosine 5'-triphosphate and guanosine 5'-triphosphate, allowed calculation of the average half-lives of these termini, which were found to be approximately 170 s at 21.5 C for both. The ratio between the number of nucleotides incorporated into the interior of RNA chains per second and the number of termini synthesized per second was calculated by several methods and found to be between 4,000 and 8,000. Assuming that the initiation of synthesis of a RNA chain by deoxyribonucleic acid-dependent RNA polymerase always produces a triphosphate termini and that some termini do not have half-lives so short as to not be seen in this study (less than 10 s), this is the apparent average length of the transcriptional unit. The implication of these findings to the genetic organization of transfer RNA genes is discussed.
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Abstract
Treatment of insect polyribosomes with 1 M KCl released a messenger ribonucleoprotein with a pronounced 16S peak. Phenol extraction resulted in a defined peak of 10S RNA, which was judged as mRNA by the following criteria: it showed specificity for binding to ribosomes, and the formation of initiation complex was dependent on protein initiation factors, GTP, mRNA, and aminoacyl-tRNA. The complex directed protein synthesis upon the addition of elongation factors. mRNA was treated with phosphatase and phosphorylated at the 5'-end with [(32)P]cyanoethylphosphate. [(32)P]mRNA was digested by T1 ribonuclease to completion and chromatographed on DEAE-cellulose. The only fragment with (32)P was 15 nucleotides long; it was treated with pancreatic ribonuclease and fingerprinted. Fractions of AC, AAC, and AAAC were found. Initiation signal AUG or GUG in these mRNAs does not begin immediately at the 5'-end and may be at a distance greater than 15 nucleotides. Alkaline hydrolysis of mRNAs labeled in vivo with [(14)C]adenosine revealed Ap and pppAp. Alkaline hydrolysis of mRNA labeled with (32)P at the 5'-terminus resulted in pAp. Hence, these results suggest that in a heterogeneous population of mRNAs from insects, all start with A and have sequence homology at the 5'-termini. This sequence may reflect the signal for RNA polymerase on the gene or may promote the binding of mRNA to ribosomes.
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Laver W. The Polypeptides of Influenza Viruses. Adv Virus Res 1973. [DOI: 10.1016/s0065-3527(08)60819-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
The ribonucleoprotein (RNP) internal components of influenza virus were separated into distinct size classes by sedimentation in glycerol gradients and examined by electron microscopy by using positive staining with uranyl acetate. The large RNP have a peak in length distribution at 90 to 110 nm, the medium, at 60 to 90 nm, and the small, at 30 to 50 nm. These lengths can be correlated with the estimated molecular weights of the ribonucleic acids contained in the various RNP size classes. The RNP structure appears to consist of a strand which is folded back on itself and coiled in a regular double-helical arrangement.
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Horst J, Content J, Mandeles S, Fraenkel-Conrat H, Duesberg P. Distinct oligonucleotide patterns of distinct influenza virus RNA's. J Mol Biol 1972; 69:209-15. [PMID: 5070866 DOI: 10.1016/0022-2836(72)90226-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Schulze IT. The structure of influenza virus. II. A model based on the morphology and composition of subviral particles. Virology 1972; 47:181-96. [PMID: 4110126 DOI: 10.1016/0042-6822(72)90251-6] [Citation(s) in RCA: 113] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Lewandowski LJ, Content J, Leppla SH. Characterization of the subunit structure of the ribonucleic acid genome of influenza virus. J Virol 1971; 8:701-7. [PMID: 4332140 PMCID: PMC376250 DOI: 10.1128/jvi.8.5.701-707.1971] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Ribonucleic acid extracted from influenza virus was labeled at the 3' termini with (3)H and analyzed by polyacrylamide gel electrophoresis. Influenza virus was found to contain a minimum of seven and possibly as many as 10 polynucleotide chains, most of which appear to terminate at the 3' end in uridine.
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Shatkin AJ. Viruses with segmented ribonucleic acid genomes: multiplication of influenza versus reovirus. BACTERIOLOGICAL REVIEWS 1971; 35:250-66. [PMID: 5114967 PMCID: PMC378389 DOI: 10.1128/br.35.3.250-266.1971] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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