The classic swine fever virus (CSFV) core protein can enhance de novo-initiated RNA synthesis by the CSFV polymerase NS5B

Li, Weiwei; Zhang, Yanming; Kao, C. Cheng

doi:10.1007/s11262-014-1080-x

Cited by 7 publications

(4 citation statements)

References 46 publications

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“…In the plus-strand viruses CSFV and norovirus, the core/capsid proteins have been reported to interact with the RdRps and to be involved in viral RNA synthesis (25,26). Here, we found that the PRRSV N protein also interacted with its RdRp, Nsp9.…”

Section: Discussionmentioning

confidence: 61%

“…In plus-strand RNA viruses, the core protein of classic swine fever virus (CSFV) and the capsid protein of norovirus have been reported to enhance their RdRp activities, and their viral RNA syntheses are regulated by the interaction between their RdRps and core/capsid proteins (25,26). A role in viral RNA synthesis has also been postulated for the N protein of coronavirus, as the expression of the nucleocapsid protein is required for the initiation of RNA synthesis in some reverse-genetic systems (27,28).…”

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confidence: 99%

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

Liu

Tian

Nan

et al. 2016

J Virol

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Porcine 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 ␣-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.

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Section: Discussionmentioning

confidence: 61%

mentioning

confidence: 99%

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

Liu

Tian

Nan

et al. 2016

J Virol

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“…Using the reporter systems, it was demonstrated that the CSFV core protein can regulate CSFV RNA synthesis by enhancing CSFV RNA-dependent RNA polymerase (NS5B) activity in a virus species-specific manner [45]. Further studies indicated that residues 21-99 of the core protein were required for enhancement of NS5B activity [45]. NS3, NS5A, and NS5B of CSFV are replication-associated proteins.…”

Section: General Applications Of Live Cell Reporter Systems Reporter mentioning

confidence: 99%

Live Cell Reporter Systems for Positive-Sense Single Strand RNA Viruses

Ren

Peng

Chen

et al. 2016

Appl Biochem Biotechnol

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Cell-based reporter systems have facilitated studies of viral replication and pathogenesis, virus detection, and drug susceptibility testing. There are three types of cell-based reporter systems that express certain reporter protein for positive-sense single strand RNA virus infections. The first type is classical reporter system, which relies on recombinant virus, reporter virus particle, or subgenomic replicon. During infection with the recombinant virus or reporter virus particle, the reporter protein is expressed and can be detected in real time in a dose-dependent manner. Using subgenomic replicon, which are genetically engineered viral RNA molecules that are capable of replication but incapable of producing virions, the translation and replication of the replicon could be tracked by the accumulation of reporter protein. The second type of reporter system involves genetically engineered cells bearing virus-specific protease cleavage sequences, which can sense the incoming viral protease. The third type is based on viral replicase, which can report the specific virus infection via detection of the incoming viral replicase. This review specifically focuses on the major technical breakthroughs in the design of cell-based reporter systems and the application of these systems to the further understanding and control of viruses over the past few decades.

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“…CSFV C protein is important for efficient viral replication via interactions with both viral proteins and cellular proteins [22]. It has been identified that C protein interacts with viral protein NS5B and enhances its RNA dependent RNA polymerase aitivity [23]. Besides, interactions of C protein with cellular proteins SUMO-1 (small ubiquitin-like modifier 1), UBC9 (a SUMO-1 conjugating enzyme) and IQGAP1 are crucial for efficient viral proliferation and viral virulence [24, 25].…”

Section: Introductionmentioning

confidence: 99%

Important roles of C-terminal residues in degradation of capsid protein of classical swine fever virus

Chen

Zhu

Fan

et al. 2019

Virol J

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BackgroundCapsid (C) protein plays an important role in the replication of classical swine fever virus (CSFV). The ubiquitin proteasome system (UPS) involves in replication of many viruses via modulation of viral proteins. The relationship of CSFV with UPS is poorly understood and the impact of 26S proteasome on C protein has never been reported before.MethodsIn this study, fused C protein with an EGFP tag is expressed in PK-15 and 3D4/2 cells. MG132 and 3-methyladenine (3-MA) are used to detect the roles of 26S proteasome and autophagolysosome in expression levels of C protein. Truncated and mutant C proteins are used to find the exact residues responsible for the degradation of C protein. Immunoprecipitaion is performed to find whether C protein is ubiquitinated or not.ResultsC-EGFP protein expresses in a cleaved form at a low level and is degraded by 26S proteasome which could be partly inhibited by MG132. C-terminal residues play more important roles in the degradation of C protein than N-terminal residues. Residues 260 to 267, especially M260 and L261, are crucial for the degradation. In addition, C-terminal residues 262 to 267 determine cleavage efficiency of C protein.ConclusionsCSFV C protein is degraded by 26S proteasome in a ubiquitin-independent manner. Last 8 residues at C-terminus of immature C protein play a major role in proteasomal degradation of CSFV C protein and determine the cleavage efficiency of C protein by signal peptide peptidase (SPP). Our findings provide valuable help for fully understanding degradation process of C protein and contribute to fully understanding the role of C protein in CSFV replication.

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The classic swine fever virus (CSFV) core protein can enhance de novo-initiated RNA synthesis by the CSFV polymerase NS5B

Cited by 7 publications

References 46 publications

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

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

Live Cell Reporter Systems for Positive-Sense Single Strand RNA Viruses

Important roles of C-terminal residues in degradation of capsid protein of classical swine fever virus

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