Many viruses suppress host gene expression in infected cells;virus-induced host gene expression inhibition is most probably beneficial for virus replication and affects viral pathogenicity. Viral proteins that induce suppression of host gene expression are often major viral virulence factors. Severe acute respiratory syndrome (SARS) is a recently emerged human disease associated with pneumonia. A novel SARS coronavirus (SCoV) is the etiological agent of SARS. We demonstrated that SCoV nsp1 protein, which is encoded at the N-terminus of the SCoV gene 1, promotes degradation of host mRNAs, but not rRNAs, leading to strong host protein synthesis inhibition in expressing cells. Further analysis suggested that nsp1 did not promote degradation of SCoV mRNA-like mRNAs, demonstrating that SCoV nsp1 protein was the first viral protein among any known viral proteins that selectively promotes degradation of host mRNAs without affecting the stabilities of viral mRNAs. Analysis of host mRNA accumulation in SCoV-infected cells and in cells infected with SCoV carrying a mutated nsp1 that no longer suppressed host gene expression strongly suggested that nsp1 promoted host mRNA degradation in infected cells. Thus, SCoV appears to use a novel strategy to suppress host gene expression. We hypothesized that SCoV nspl promotes degradation of host mRNAs in infected cells as a means to suppress accumulation of various """"""""hostile"""""""" host- cell proteins;to promote its own replication, SCoV may suppress antiviral proteins, like type I interferon, and proapoptotic proteins to prevent early cell death, and suppression of cellular proteins involved in both innate and acquired immunities may allow the virus to circumvent host immune recognition, and/or induction responses. Also the nsp1-induced host mRNA degradation may be beneficial for efficient translation of SCoV proteins. We suspect that nsp1 may be a major SCoV virulence factor. The present application proposes: to uncover the mechanisms of nsp1-induced host mRNA degradation using in vitro systems;to identify host proteins that interact with nsp1, which might yield clues about nsp1 selectively leading to degradation of mRNA vs. rRNA;to clarify why SCoV mRNAs were resistant to the nsp1-induced mRNA destabilization;and to examine whether some host mRNA species are also resistant to nsp1-induced host mRNA destabilization. Furthermore, we will use SCoV and its mutant carrying an altered nsp1 that no longer promotes host mRNA degradation to establish the role of nsp1 in suppressing host gene expression in infected cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI072493-05
Application #
8117243
Study Section
Virology - B Study Section (VIRB)
Program Officer
Salomon, Rachelle
Project Start
2007-08-05
Project End
2013-07-31
Budget Start
2011-08-01
Budget End
2013-07-31
Support Year
5
Fiscal Year
2011
Total Cost
$290,366
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
800771149
City
Galveston
State
TX
Country
United States
Zip Code
77555
Narayanan, Krishna; Ramirez, Sydney I; Lokugamage, Kumari G et al. (2015) Coronavirus nonstructural protein 1: Common and distinct functions in the regulation of host and viral gene expression. Virus Res 202:89-100
Terasaki, Kaori; Won, Sungyong; Makino, Shinji (2013) The C-terminal region of Rift Valley fever virus NSm protein targets the protein to the mitochondrial outer membrane and exerts antiapoptotic function. J Virol 87:676-82
Narayanan, Krishna; Makino, Shinji (2013) Interplay between viruses and host mRNA degradation. Biochim Biophys Acta 1829:732-41
Lokugamage, Kumari G; Narayanan, Krishna; Huang, Cheng et al. (2012) Severe acute respiratory syndrome coronavirus protein nsp1 is a novel eukaryotic translation inhibitor that represses multiple steps of translation initiation. J Virol 86:13598-608
de Wilde, Adriaan H; Zevenhoven-Dobbe, Jessika C; van der Meer, Yvonne et al. (2011) Cyclosporin A inhibits the replication of diverse coronaviruses. J Gen Virol 92:2542-8
Neuman, Benjamin W; Kiss, Gabriella; Kunding, Andreas H et al. (2011) A structural analysis of M protein in coronavirus assembly and morphology. J Struct Biol 174:11-22
Huang, Cheng; Lokugamage, Kumari G; Rozovics, Janet M et al. (2011) SARS coronavirus nsp1 protein induces template-dependent endonucleolytic cleavage of mRNAs: viral mRNAs are resistant to nsp1-induced RNA cleavage. PLoS Pathog 7:e1002433
Huang, Cheng; Lokugamage, Kumari G; Rozovics, Janet M et al. (2011) Alphacoronavirus transmissible gastroenteritis virus nsp1 protein suppresses protein translation in mammalian cells and in cell-free HeLa cell extracts but not in rabbit reticulocyte lysate. J Virol 85:638-43
Kamitani, Wataru; Huang, Cheng; Narayanan, Krishna et al. (2009) A two-pronged strategy to suppress host protein synthesis by SARS coronavirus Nsp1 protein. Nat Struct Mol Biol 16:1134-40
Tohya, Yukinobu; Narayanan, Krishna; Kamitani, Wataru et al. (2009) Suppression of host gene expression by nsp1 proteins of group 2 bat coronaviruses. J Virol 83:5282-8

Showing the most recent 10 out of 12 publications