scholarly journals Roles of Phosphorylation of the Nucleocapsid Protein of Mumps Virus in Regulating Viral RNA Transcription and Replication

2015 ◽  
Vol 89 (14) ◽  
pp. 7338-7347 ◽  
Author(s):  
James Zengel ◽  
Adrian Pickar ◽  
Pei Xu ◽  
Alita Lin ◽  
Biao He
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Synthesis ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Mumps Virus ◽  
Viral Rna ◽  
Human Populations ◽  
Rna Genome ◽  
Major Phosphorylation Site ◽  
Transcription And Replication

ABSTRACTMumps virus (MuV) is a paramyxovirus with a negative-sense nonsegmented RNA genome. The viral RNA genome is encapsidated by the nucleocapsid protein (NP) to form the ribonucleoprotein (RNP), which serves as a template for transcription and replication. In this study, we investigated the roles of phosphorylation sites of NP in MuV RNA synthesis. Using radioactive labeling, we first demonstrated that NP was phosphorylated in MuV-infected cells. Using both liquid chromatography-mass spectrometry (LC-MS) andin silicomodeling, we identified nine putative phosphorylated residues within NP. We mutated these nine residues to alanine. Mutation of the serine residue at position 439 to alanine (S439A) was found to reduce the phosphorylation of NP in transfected cells by over 90%. The effects of these mutations on the MuV minigenome system were examined. The S439A mutant was found to have higher activity, four mutants had lower activity, and four mutants had similar activity compared to wild-type NP. MuV containing the S439A mutation had 90% reduced phosphorylation of NP and enhanced viral RNA synthesis and viral protein expression at early time points after infection, indicating that S439 is the major phosphorylation site of NP and its phosphorylation plays an important role in downregulating viral RNA synthesis.IMPORTANCEMumps virus (MuV), a paramyxovirus, is an important human pathogen that is reemerging in human populations. Nucleocapsid protein (NP) of MuV is essential for viral RNA synthesis. We have identified the major phosphorylation site of NP. We have found that phosphorylation of NP plays a critical role in regulating viral RNA synthesis. The work will lead to a better understanding of viral RNA synthesis and possible novel targets for antiviral drug development.

scholarly journals Mumps Virus Nucleoprotein Enhances Phosphorylation of the Phosphoprotein by Polo-Like Kinase 1

2015 ◽  
Vol 90 (3) ◽  
pp. 1588-1598 ◽  
Author(s):  
Adrian Pickar ◽  
James Zengel ◽  
Pei Xu ◽  
Zhuo Li ◽  
Biao He
Keyword(s):  
Rna Synthesis ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Mumps Virus ◽  
Viral Rna ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Rna Complex ◽  
Viral Genomic Rna ◽  
Negative Sense

ABSTRACTThe viral RNA-dependent RNA polymerases (vRdRps) of nonsegmented, negative-sense viruses (NNSVs) consist of the enzymatic large protein (L) and the phosphoprotein (P). P is heavily phosphorylated, and its phosphorylation plays a critical role in viral RNA synthesis. Since NNSVs do not encode kinases, P is phosphorylated by host kinases. In this study, we investigate the roles that viral proteins play in the phosphorylation of mumps virus (MuV) P. We found that nucleoprotein (NP) enhances the phosphorylation of P. We have identified the serine/threonine kinase Polo-like kinase 1 (PLK1) as a host kinase that phosphorylates P and have found that phosphorylation of P by PLK1 is enhanced by NP. The PLK1 binding site in MuV P was mapped to residues 146 to 148 within the S(pS/T)P motif, and the phosphorylation site was identified as residues S292 and S294.IMPORTANCEIt has previously been shown that P acts as a chaperone for NP, which encapsidates viral genomic RNA to form the NP-RNA complex, the functional template for viral RNA synthesis. Thus, it is assumed that phosphorylation of P may regulate NP's ability to form the NP-RNA complex, thereby regulating viral RNA synthesis. Our work demonstrates that MuV NP affects phosphorylation of P, suggesting that NP can regulate viral RNA synthesis by regulating phosphorylation of P.

scholarly journals Nucleocapsid Structure of Negative Strand RNA Virus

Viruses ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 835 ◽  
Author(s):  
Ming Luo ◽  
James Ross Terrell ◽  
Shelby Ashlyn Mcmanus
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Synthesis ◽  
Ebola Virus ◽  
Rna Virus ◽  
Viral Rna ◽  
Human Pathogens ◽  
Negative Strand ◽  
Rna Genome ◽  
Rna Complex ◽  
Unique Mechanism

Negative strand RNA viruses (NSVs) include many important human pathogens, such as influenza virus, Ebola virus, and rabies virus. One of the unique characteristics that NSVs share is the assembly of the nucleocapsid and its role in viral RNA synthesis. In NSVs, the single strand RNA genome is encapsidated in the linear nucleocapsid throughout the viral replication cycle. Subunits of the nucleocapsid protein are parallelly aligned along the RNA genome that is sandwiched between two domains composed of conserved helix motifs. The viral RNA-dependent-RNA polymerase (vRdRp) must recognize the protein–RNA complex of the nucleocapsid and unveil the protected genomic RNA in order to initiate viral RNA synthesis. In addition, vRdRp must continuously translocate along the protein–RNA complex during elongation in viral RNA synthesis. This unique mechanism of viral RNA synthesis suggests that the nucleocapsid may play a regulatory role during NSV replication.

scholarly journals Releasing the Genomic RNA Sequestered in the Mumps Virus Nucleocapsid

2016 ◽  
Vol 90 (22) ◽  
pp. 10113-10119 ◽  
Author(s):  
Chelsea Severin ◽  
James R. Terrell ◽  
James R. Zengel ◽  
Robert Cox ◽  
Richard K. Plemper ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Nucleocapsid Protein ◽  
Rna Synthesis ◽  
Rna Virus ◽  
Mumps Virus ◽  
Viral Rna ◽  
Genomic Rna ◽  
Rna Dependent Rna Polymerase ◽  
Negative Strand ◽  
Viral Rdrp

ABSTRACT In a negative-strand RNA virus, the genomic RNA is sequestered inside the nucleocapsid when the viral RNA-dependent RNA polymerase uses it as the template for viral RNA synthesis. It must require a conformational change in the nucleocapsid protein (N) to make the RNA accessible to the viral polymerase during this process. The structure of an empty mumps virus (MuV) nucleocapsid-like particle was determined to 10.4-Å resolution by cryo-electron microscopy (cryo-EM) image reconstruction. By modeling the crystal structure of parainfluenza virus 5 into the density, it was shown that the α-helix close to the RNA became flexible when RNA was removed. Point mutations in this helix resulted in loss of polymerase activities. Since the core of N is rigid in the nucleocapsid, we suggest that interactions between this region of the mumps virus N and its polymerase, instead of large N domain rotations, lead to exposure of the sequestered genomic RNA. IMPORTANCE Mumps virus (MuV) infection may cause serious diseases, including hearing loss, orchitis, oophoritis, mastitis, and pancreatitis. MuV is a negative-strand RNA virus, similar to rabies virus or Ebola virus, that has a unique mechanism of viral RNA synthesis. They all make their own RNA-dependent RNA polymerase (RdRp). The viral RdRp uses the genomic RNA inside the viral nucleocapsid as the template to synthesize viral RNAs. Since the template RNA is always sequestered in the nucleocapsid, the viral RdRp must find a way to open it up in order to gain access to the covered template. Our work reported here shows that a helix structural element in the MuV nucleocapsid protein becomes open when the sequestered RNA is released. The amino acids related to this helix are required for RdRp to synthesize viral RNA. We propose that the viral RdRp pulls this helix open to release the genomic RNA.

scholarly journals Going beyond Integration: The Emerging Role of HIV-1 Integrase in Virion Morphogenesis

Viruses ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1005 ◽  
Author(s):  
Jennifer L. Elliott ◽  
Sebla B. Kutluay
Keyword(s):  
Life Cycle ◽  
Viral Genome ◽  
Critical Role ◽  
Viral Rna ◽  
Target Cells ◽  
Host Chromosome ◽  
Virion Morphogenesis ◽  
Rna Genome ◽  
Hiv 1

The HIV-1 integrase enzyme (IN) plays a critical role in the viral life cycle by integrating the reverse-transcribed viral DNA into the host chromosome. This function of IN has been well studied, and the knowledge gained has informed the design of small molecule inhibitors that now form key components of antiretroviral therapy regimens. Recent discoveries unveiled that IN has an under-studied yet equally vital second function in human immunodeficiency virus type 1 (HIV-1) replication. This involves IN binding to the viral RNA genome in virions, which is necessary for proper virion maturation and morphogenesis. Inhibition of IN binding to the viral RNA genome results in mislocalization of the viral genome inside the virus particle, and its premature exposure and degradation in target cells. The roles of IN in integration and virion morphogenesis share a number of common elements, including interaction with viral nucleic acids and assembly of higher-order IN multimers. Herein we describe these two functions of IN within the context of the HIV-1 life cycle, how IN binding to the viral genome is coordinated by the major structural protein, Gag, and discuss the value of targeting the second role of IN in virion morphogenesis.

scholarly journals Zinc Finger-Containing Cellular Transcription Corepressor ZBTB25 Promotes Influenza Virus RNA Transcription and Is a Target for Zinc Ejector Drugs

2017 ◽  
Vol 91 (20) ◽  
Author(s):  
Shu-Chuan Chen ◽  
King-Song Jeng ◽  
Michael M. C. Lai
Keyword(s):  
Viral Replication ◽  
Zinc Finger ◽  
Rna Synthesis ◽  
Viral Rna ◽  
Interferon Production ◽  
Zinc Finger Domain ◽  
Rna Transcription ◽  
Viral Rdrp ◽  
Cellular Factors ◽  
Transcription And Replication

ABSTRACT Influenza A virus (IAV) replication relies on an intricate interaction between virus and host cells. How the cellular proteins are usurped for IAV replication remains largely obscure. The aim of this study was to search for novel and potential cellular factors that participate in IAV replication. ZBTB25, a transcription repressor of a variety of cellular genes, was identified by an RNA interference (RNAi) genomic library screen. Depletion of ZBTB25 significantly reduced IAV production. Conversely, overexpression of ZBTB25 enhanced it. ZBTB25 interacted with the viral RNA-dependent RNA polymerase (RdRp) protein and modulated its transcription activity. In addition, ZBTB25 also functioned as a viral RNA (vRNA)-binding protein, binding preferentially to the U-rich sequence within the 5′ untranslated region (UTR) of vRNA. Both protein-protein and protein-RNA interactions involving ZBTB25 facilitated viral RNA transcription and replication. In addition, ZBTB25 suppressed interferon production, further enhancing viral replication. ZBTB25-associated functions required an intact zinc finger domain and posttranslational SUMO-1 modification of ZBTB25. Furthermore, treatment with disulfiram (a zinc ejector) of ZBTB25-overexpressing cells showed significantly reduced IAV production as a result of reduced RNA synthesis. Our findings indicate that IAV usurps ZBTB25 for IAV RNA synthesis and serves as a novel and potential therapeutic antiviral target. IMPORTANCE IAV-induced seasonal influenza causes severe illness and death in high-risk populations. However, IAV has developed resistance to current antiviral drugs due to its high mutation rate. Therefore, development of drugs targeting cellular factors required for IAV replication is an attractive alternative for IAV therapy. Here, we discovered a cellular protein, ZBTB25, that enhances viral RdRp activity by binding to both viral RdRp and viral RNA to stimulate viral RNA synthesis. A unique feature of ZBTB25 in the regulation of viral replication is its dual transcription functions, namely, promoting viral RNA transcription through binding to the U-rich region of vRNA and suppressing cellular interferon production. ZBTB25 contains a zinc finger domain that is required for RNA-inhibitory activity by chelating zinc ions. Disulfiram treatment disrupts the zinc finger functions, effectively repressing IAV replication. Based on our findings, we demonstrate that ZBTB25 regulates IAV RNA transcription and replication and serves as a promising antiviral target for IAV treatment.

scholarly journals An RNA Pseudoknot in the 3′ End of the Arterivirus Genome Has a Critical Role in Regulating Viral RNA Synthesis

2007 ◽  
Vol 81 (17) ◽  
pp. 9426-9436 ◽  
Author(s):  
Nancy Beerens ◽  
Eric J. Snijder
Keyword(s):  
Rna Synthesis ◽  
Critical Role ◽  
Equine Arteritis Virus ◽  
Viral Rna ◽  
Replicase Gene ◽  
Loop Structure ◽  
Minus Strand ◽  
Stem Loop ◽  
Loop Region ◽  
Stem Loop Structure

ABSTRACT In the life cycle of plus-strand RNA viruses, the genome initially serves as the template for both translation of the viral replicase gene and synthesis of minus-strand RNA and is ultimately packaged into progeny virions. These various processes must be properly balanced to ensure efficient viral proliferation. To achieve this, higher-order RNA structures near the termini of a variety of RNA virus genomes are thought to play a key role in regulating the specificity and efficiency of viral RNA synthesis. In this study, we have analyzed the signals for minus-strand RNA synthesis in the prototype of the arterivirus family, equine arteritis virus (EAV). Using site-directed mutagenesis and an EAV reverse genetics system, we have demonstrated that a stem-loop structure near the 3′ terminus of the EAV genome is required for RNA synthesis. We have also obtained evidence for an essential pseudoknot interaction between the loop region of this stem-loop structure and an upstream hairpin residing in the gene encoding the nucleocapsid protein. We propose that the formation of this pseudoknot interaction may constitute a molecular switch that could regulate the specificity or timing of viral RNA synthesis. This hypothesis is supported by the fact that phylogenetic analysis predicted the formation of similar pseudoknot interactions near the 3′ end of all known arterivirus genomes, suggesting that this interaction has been conserved in evolution.

scholarly journals Porcine Reproductive and Respiratory Syndrome Virus Nucleocapsid Protein Interacts with Nsp9 and Cellular DHX9 To Regulate Viral RNA Synthesis

2016 ◽  
Vol 90 (11) ◽  
pp. 5384-5398 ◽  
Author(s):  
Long Liu ◽  
Jiao Tian ◽  
Hao Nan ◽  
Mengmeng Tian ◽  
Yuan Li ◽  
...  
Keyword(s):  
Rna Synthesis ◽  
Nonstructural Protein ◽  
Critical Role ◽  
Continuous Extension ◽  
Rna Helicase ◽  
Viral Rna ◽  
Respiratory Syndrome Virus ◽  
Nascent Transcript ◽  
Multifunctional Protein ◽  
N Protein

ABSTRACTPorcine reproductive and respiratory syndrome virus (PRRSV) nucleocapsid (N) protein is the main component of the viral capsid to encapsulate viral RNA, and it is also a multifunctional protein involved in the regulation of host cell processes. Nonstructural protein 9 (Nsp9) is the RNA-dependent RNA polymerase that plays a critical role in viral RNA transcription and replication. In this study, we demonstrate that PRRSV N protein is bound to Nsp9 by protein-protein interaction and that the contacting surface on Nsp9 is located in the two predicted α-helixes formed by 48 residues at the C-terminal end of the protein. Mutagenesis analyses identified E646, E608, and E611 on Nsp9 and Q85 on the N protein as the pivotal residues participating in the N-Nsp9 interaction. By overexpressing the N protein binding fragment of Nsp9 in infected Marc-145 cells, the synthesis of viral RNAs, as well as the production of infectious progeny viruses, was dramatically inhibited, suggesting that Nsp9-N protein association is involved in the process of viral RNA production. In addition, we show that PRRSV N interacts with cellular RNA helicase DHX9 and redistributes the protein into the cytoplasm. Knockdown of DHX9 increased the ratio of short subgenomic mRNAs (sgmRNAs); in contrast, DHX9 overexpression benefited the synthesis of longer sgmRNAs and the viral genomic RNA (gRNA). These results imply that DHX9 is recruited by the N protein in PRRSV infection to regulate viral RNA synthesis. We postulate that N and DHX9 may act as antiattenuation factors for the continuous elongation of nascent transcript during negative-strand RNA synthesis.IMPORTANCEIt is unclear whether the N protein of PRRSV is involved in regulation of the viral RNA production process. In this report, we demonstrate that the N protein of the arterivirus PRRSV participates in viral RNA replication and transcription through interacting with Nsp9 and its RdRp and recruiting cellular RNA helicase to promote the production of longer viral sgmRNAs and gRNA. Our data here provide some new insights into the discontinuous to continuous extension of PRRSV RNA synthesis and also offer a new potential anti-PRRSV strategy targeting the N-Nsp9 and/or N-DHX9 interaction.

scholarly journals Oligomerization of Mumps Virus Phosphoprotein

2015 ◽  
Vol 89 (21) ◽  
pp. 11002-11010 ◽  
Author(s):  
Adrian Pickar ◽  
Andrew Elson ◽  
Yang Yang ◽  
Pei Xu ◽  
Ming Luo ◽  
...  
Keyword(s):  
Rna Synthesis ◽  
Mutational Analysis ◽  
Mumps Virus ◽  
Viral Rna ◽  
Large Protein ◽  
Terminal Domain ◽  
P Protein ◽  
Minigenome System ◽  
Oligomerization Domain

ABSTRACTThe mumps virus (MuV) genome encodes a phosphoprotein (P) that is important for viral RNA synthesis. P forms the viral RNA-dependent RNA polymerase with the large protein (L). P also interacts with the viral nucleoprotein (NP) and self-associates to form a homotetramer. The P protein consists of three domains, the N-terminal domain (PN), the oligomerization domain (PO), and the C-terminal domain (PC). While PNis known to relax the NP-bound RNA genome, the roles of POand PCare not clear. In this study, we investigated the roles of POand PCin viral RNA synthesis using mutational analysis and a minigenome system. We found that PNand PCfunctions can betrans-complemented. However, this complementation requires PO, indicating that POis essential for P function. Using thistrans-complementation system, we found that P forms parallel dimers (PNto PNand PCto PC). Furthermore, we found that residues R231, K238, K253, and K260 in POare critical for P's functions. We identified PCto be the domain that interacts with L. These results provide structure-function insights into the role of MuV P.IMPORTANCEMuV, a paramyxovirus, is an important human pathogen. The P protein of MuV is critical for viral RNA synthesis. In this work, we established a novel minigenome system that allows the domains of P to be complemented intrans. Using this system, we confirmed that MuV P forms parallel dimers. An understanding of viral RNA synthesis will allow the design of better vaccines and the development of antivirals.

scholarly journals Complementary Mutations in the N and L Proteins for Restoration of Viral RNA Synthesis

2018 ◽  
Vol 92 (22) ◽  
Author(s):  
Weike Li ◽  
Ryan H. Gumpper ◽  
Yusuf Uddin ◽  
Ingeborg Schmidt-Krey ◽  
Ming Luo
Keyword(s):  
Rna Polymerase ◽  
Conformational Changes ◽  
Rna Synthesis ◽  
Large Subunit ◽  
Viral Rna ◽  
Structural Motif ◽  
General Mechanism ◽  
Rna Dependent Rna Polymerase ◽  
N Protein ◽  
Rna Genome

ABSTRACTDuring viral RNA synthesis by the viral RNA-dependent RNA polymerase (vRdRp) of vesicular stomatitis virus, the sequestered RNA genome must be released from the nucleocapsid in order to serve as the template. Unveiling the sequestered RNA by interactions of vRdRp proteins, the large subunit (L) and the phosphoprotein (P), with the nucleocapsid protein (N) must not disrupt the nucleocapsid assembly. We noticed that a flexible structural motif composed of an α-helix and a loop in the N protein may act as the access gate to the sequestered RNA. This suggests that local conformational changes in this structural motif may be induced by interactions with the polymerase to unveil the sequestered RNA, without disrupting the nucleocapsid assembly. Mutations of several residues in this structural motif—Glu169, Phe171, and Leu174—to Ala resulted in loss of viral RNA synthesis in a minigenome assay. After implementing these mutations in the viral genome, mutant viruses were recovered by reverse genetics and serial passages. Sequencing the genomes of the mutant viruses revealed that compensatory mutations in L, P, and N were required to restore the viral viability. Corresponding mutations were introduced in L, P, and N, and their complementarity to the N mutations was confirmed by the minigenome assay. Introduction of the corresponding mutations is also sufficient to rescue the mutant viruses. These results suggested that the interplay of the N structural motif with the L protein may play a role in accessing the nucleotide template without disrupting the overall structure of the nucleocapsid.IMPORTANCEDuring viral RNA synthesis of a negative-strand RNA virus, the viral RNA-dependent RNA polymerase (vRdRp) must gain access to the sequestered RNA in the nucleocapsid to use it as the template, but at the same time may not disrupt the nucleocapsid assembly. Our structural and mutagenesis studies showed that a flexible structural motif acts as a potential access gate to the sequestered RNA and plays an essential role in viral RNA synthesis. Interactions of this structural motif within the vRdRp may be required for unveiling the sequestered RNA. This mechanism of action allows the sequestered RNA to be released locally without disrupting the overall structure of the nucleocapsid. Since this flexible structural motif is present in the N proteins of many NSVs, release of the sequestered RNA genome by local conformational changes in the N protein may be a general mechanism in NSV viral RNA synthesis.

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