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Swaminath S, Mendes M, Zhang Y, Remick KA, Mejia I, Güereca M, te Velthuis AJ, Russell AB. Efficient genome replication in influenza A virus requires NS2 and sequence beyond the canonical promoter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.10.612348. [PMID: 39314307 PMCID: PMC11419028 DOI: 10.1101/2024.09.10.612348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 09/25/2024]
Abstract
Influenza A virus encodes promoters in both the sense and antisense orientations. These support the generation of new genomes, antigenomes, and mRNA transcripts. Using minimal replication assays-transfections with viral polymerase, nucleoprotein, and a genomic template-the influenza promoter sequences were identified as 13nt at the 5' end of the viral genomic RNA (U13) and 12nt at the 3' end (U12). Other than the fourth 3' nucleotide, the U12 and U13 sequences are identical between all eight RNA molecules that comprise the segmented influenza genome. Despite possessing identical promoters, individual segments can exhibit different transcriptional dynamics during infection. However flu promoter sequences were defined in experiments without influenza NS2, a protein which modulates transcription and replication differentially between genomic segments. This suggests that the identity of the "complete" promoter may depend on NS2. Here we assess how internal sequences of two genomic segments, HA and PB1, may contribute to NS2-dependent replication as well as map such interactions down to individual nucleotides in PB1. We find that the expression of NS2 significantly alters sequence requirements for efficient replication beyond the identical U12 and U13 sequence, providing a mechanism for the divergent replication and transcription dynamics across the influenza A virus genome.
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Affiliation(s)
- Sharmada Swaminath
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Marisa Mendes
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Yipeng Zhang
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Kaleigh A. Remick
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Isabel Mejia
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Melissa Güereca
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Aartjan J.W. te Velthuis
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Alistair B. Russell
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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2
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Sun J, Kuai L, Zhang L, Xie Y, Zhang Y, Li Y, Peng Q, Shao Y, Yang Q, Tian WX, Zhu J, Qi J, Shi Y, Deng T, Gao GF. NS2 induces an influenza A RNA polymerase hexamer and acts as a transcription to replication switch. EMBO Rep 2024:10.1038/s44319-024-00208-4. [PMID: 39026012 DOI: 10.1038/s44319-024-00208-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Revised: 07/03/2024] [Accepted: 07/05/2024] [Indexed: 07/20/2024] Open
Abstract
Genome transcription and replication of influenza A virus (FluA), catalyzed by viral RNA polymerase (FluAPol), are delicately controlled across the virus life cycle. A switch from transcription to replication occurring at later stage of an infection is critical for progeny virion production and viral non-structural protein NS2 has been implicated in regulating the switch. However, the underlying regulatory mechanisms and the structure of NS2 remained elusive for years. Here, we determine the cryo-EM structure of the FluAPol-NS2 complex at ~3.0 Å resolution. Surprisingly, three domain-swapped NS2 dimers arrange three symmetrical FluPol dimers into a highly ordered barrel-like hexamer. Further structural and functional analyses demonstrate that NS2 binding not only hampers the interaction between FluAPol and the Pol II CTD because of steric conflicts, but also impairs FluAPol transcriptase activity by stalling it in the replicase conformation. Moreover, this is the first visualization of the full-length NS2 structure. Our findings uncover key molecular mechanisms of the FluA transcription-replication switch and have implications for the development of antivirals.
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Affiliation(s)
- Junqing Sun
- College of Veterinary Medicine, Shanxi Agricultural University, Jinzhong, 030801, China
- Shanxi Academy of Advanced Research and Innovation, Taiyuan, 030032, China
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Lu Kuai
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Lei Zhang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- Institute of Pediatrics, Shenzhen Children's Hospital, Shenzhen, 518026, China
| | - Yufeng Xie
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Yanfang Zhang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yan Li
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Qi Peng
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yuekun Shao
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Qiuxian Yang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wen-Xia Tian
- College of Veterinary Medicine, Shanxi Agricultural University, Jinzhong, 030801, China
| | - Junhao Zhu
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jianxun Qi
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yi Shi
- Shanxi Academy of Advanced Research and Innovation, Taiyuan, 030032, China.
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
- International Institute of Vaccine Research and Innovation (iVac), Savaid Medical School, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Tao Deng
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - George F Gao
- Shanxi Academy of Advanced Research and Innovation, Taiyuan, 030032, China.
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
- International Institute of Vaccine Research and Innovation (iVac), Savaid Medical School, University of Chinese Academy of Sciences, Beijing, 100049, China.
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3
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Teo QW, Wang Y, Lv H, Mao KJ, Tan TJC, Huan YW, Rivera-Cardona J, Shao EK, Choi D, Dargani ZT, Brooke CB, Wu NC. Deep mutational scanning of influenza A virus NEP reveals pleiotropic mutations in its N-terminal domain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.16.594574. [PMID: 38798526 PMCID: PMC11118461 DOI: 10.1101/2024.05.16.594574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
The influenza A virus nuclear export protein (NEP) is a multifunctional protein that is essential for the viral life cycle and has very high sequence conservation. However, since the open reading frame of NEP largely overlaps with that of another influenza viral protein, non-structural protein 1, it is difficult to infer the functional constraints of NEP based on sequence conservation analysis. Besides, the N-terminal of NEP is structurally disordered, which further complicates the understanding of its function. Here, we systematically measured the replication fitness effects of >1,800 mutations of NEP. Our results show that the N-terminal domain has high mutational tolerance. Additional experiments demonstrate that N-terminal domain mutations pleiotropically affect viral transcription and replication dynamics, host cellular responses, and mammalian adaptation of avian influenza virus. Overall, our study not only advances the functional understanding of NEP, but also provides insights into its evolutionary constraints.
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Li YJ, Chen CY, Kuo YS, Huang YW, Kuo RL, Chang LK, Yang JH, Lai CH, Shih SR, Chiu YF. OTUB1 contributes to the stability and function of Influenza A virus NS2. PLoS Pathog 2024; 20:e1012279. [PMID: 38814988 PMCID: PMC11166342 DOI: 10.1371/journal.ppat.1012279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 06/11/2024] [Accepted: 05/20/2024] [Indexed: 06/01/2024] Open
Abstract
The influenza A virus (IAV) consists of 8 single-stranded, negative-sense viral RNA (vRNA) segments. After infection, vRNA is transcribed, replicated, and wrapped by viral nucleoprotein (NP) to form viral ribonucleoprotein (vRNP). The transcription, replication, and nuclear export of the viral genome are regulated by the IAV protein, NS2, which is translated from spliced mRNA transcribed from viral NS vRNA. This splicing is inefficient, explaining why NS2 is present in low abundance after IAV infection. The levels of NS2 and its subsequent accumulation are thought to influence viral RNA replication and vRNP nuclear export. Here we show that NS2 is ubiquitinated at the K64 and K88 residues by K48-linked and K63-linked polyubiquitin (polyUb) chains, leading to the degradation of NS2 by the proteasome. Additionally, we show that a host deubiquitinase, OTUB1, can remove polyUb chains conjugated to NS2, thereby stabilizing NS2. Accordingly, knock down of OTUB1 by siRNA reduces the nuclear export of vRNP, and reduces the overall production of IAV. These results collectively demonstrate that the levels of NS2 in IAV-infected cells are regulated by a ubiquitination-deubiquitination system involving OTUB1 that is necessary for optimal IAV replication.
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Affiliation(s)
- Yu-Jyun Li
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan
| | - Chi-Yuan Chen
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
| | - Yu-Shen Kuo
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan
| | - Yi-Wen Huang
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan
| | - Rei-Lin Kuo
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan
| | - Li-Kwan Chang
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Jeng-How Yang
- Division of Infectious Diseases, Department of Medicine, Chang Gung Memorial Hospital, New Taipei, Taiwan
| | - Chih-Ho Lai
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan
| | - Shin-Ru Shih
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan
| | - Ya-Fang Chiu
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan
- Division of Infectious Diseases, Department of Medicine, Chang Gung Memorial Hospital, New Taipei, Taiwan
- Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan, Taiwan
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5
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Khalil AM, Nogales A, Martínez-Sobrido L, Mostafa A. Antiviral responses versus virus-induced cellular shutoff: a game of thrones between influenza A virus NS1 and SARS-CoV-2 Nsp1. Front Cell Infect Microbiol 2024; 14:1357866. [PMID: 38375361 PMCID: PMC10875036 DOI: 10.3389/fcimb.2024.1357866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 01/16/2024] [Indexed: 02/21/2024] Open
Abstract
Following virus recognition of host cell receptors and viral particle/genome internalization, viruses replicate in the host via hijacking essential host cell machinery components to evade the provoked antiviral innate immunity against the invading pathogen. Respiratory viral infections are usually acute with the ability to activate pattern recognition receptors (PRRs) in/on host cells, resulting in the production and release of interferons (IFNs), proinflammatory cytokines, chemokines, and IFN-stimulated genes (ISGs) to reduce virus fitness and mitigate infection. Nevertheless, the game between viruses and the host is a complicated and dynamic process, in which they restrict each other via specific factors to maintain their own advantages and win this game. The primary role of the non-structural protein 1 (NS1 and Nsp1) of influenza A viruses (IAV) and the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively, is to control antiviral host-induced innate immune responses. This review provides a comprehensive overview of the genesis, spatial structure, viral and cellular interactors, and the mechanisms underlying the unique biological functions of IAV NS1 and SARS-CoV-2 Nsp1 in infected host cells. We also highlight the role of both non-structural proteins in modulating viral replication and pathogenicity. Eventually, and because of their important role during viral infection, we also describe their promising potential as targets for antiviral therapy and the development of live attenuated vaccines (LAV). Conclusively, both IAV NS1 and SARS-CoV-2 Nsp1 play an important role in virus-host interactions, viral replication, and pathogenesis, and pave the way to develop novel prophylactic and/or therapeutic interventions for the treatment of these important human respiratory viral pathogens.
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Affiliation(s)
- Ahmed Magdy Khalil
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
- Department of Zoonotic Diseases, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt
| | - Aitor Nogales
- Center for Animal Health Research, CISA-INIA-CSIC, Madrid, Spain
| | - Luis Martínez-Sobrido
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
| | - Ahmed Mostafa
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
- Center of Scientific Excellence for Influenza Viruses, National Research Centre, Giza, Egypt
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6
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Zhang L, Shao Y, Wang Y, Yang Q, Guo J, Gao GF, Deng T. Twenty natural amino acid substitution screening at the last residue 121 of influenza A virus NS2 protein reveals the critical role of NS2 in promoting virus genome replication by coordinating with viral polymerase. J Virol 2024; 98:e0116623. [PMID: 38054704 PMCID: PMC10804943 DOI: 10.1128/jvi.01166-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 11/20/2023] [Indexed: 12/07/2023] Open
Abstract
Both influenza A virus genome transcription (vRNA→mRNA) and replication (vRNA→cRNA→vRNA), catalyzed by the influenza RNA polymerase (FluPol), are dynamically regulated across the virus life cycle. It has been reported that the last amino acid I121 of the viral NS2 protein plays a critical role in promoting viral genome replication in influenza mini-replicon systems. Here, we performed a 20 natural amino acid substitution screening at residue NS2-I121 in the context of virus infection. We found that the hydrophobicity of the residue 121 is essential for virus survival. Interestingly, through serial passage of the rescued mutant viruses, we further identified adaptive mutations PA-K19E and PB1-S713N on FluPol which could effectively compensate for the replication-promoting defect caused by NS2-I121 mutation in the both mini-replicon and virus infection systems. Structural analysis of different functional states of FluPol indicates that PA-K19E and PB1-S713N could stabilize the replicase conformation of FluPol. By using a cell-based NanoBiT complementary reporter assay, we further demonstrate that both wild-type NS2 and PA-K19E/PB1-S713N could enhance FluPol dimerization, which is necessary for genome replication. These results reveal the critical role NS2 plays in promoting viral genome replication by coordinating with FluPol.IMPORTANCEThe intrinsic mechanisms of influenza RNA polymerase (FluPol) in catalyzing viral genome transcription and replication have been largely resolved. However, the mechanisms of how transcription and replication are dynamically regulated remain elusive. We recently reported that the last amino acid of the viral NS2 protein plays a critical role in promoting viral genome replication in an influenza mini-replicon system. Here, we conducted a 20 amino acid substitution screening at the last residue 121 in virus rescue and serial passage. Our results demonstrate that the replication-promoting function of NS2 is important for virus survival and efficient multiplication. We further show evidence that NS2 and NS2-I121 adaptive mutations PA-K19E/PB1-S713N regulate virus genome replication by promoting FluPol dimerization. This work highlights the coordination between NS2 and FluPol in fulfilling efficient genome replication. It further advances our understanding of the regulation of viral RNA synthesis for influenza A virus.
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Affiliation(s)
- Lei Zhang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- />Institute of Pediatrics, Shenzhen Children’s Hospital, Shenzhen, China
| | - Yuekun Shao
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yingying Wang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Qiuxian Yang
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Jiamei Guo
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - George F. Gao
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Tao Deng
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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