The NS1 protein of influenza A virus is a master regulator of the type I IFN-mediated antiviral response induced during viral infection. An important step of this response that is inhibited by this protein is the activation of transcription factors involved in IFN synthesis by the cytoplasmic RNA sensor of viral infection RIG-I. In collaboration with Dr. Jung, overall PI of this U19 proposal, we have found that the NS1 prevents activation of RIG-I by inhibiting its ubiquitination. Specifically, the NS1 binds to and inhibit TRIM25, a cellular ubiquitin ligase that ubiquitinates RIG-I, a process required for RIG-I downstream signaling. Our preliminary evidence also indicates that a mutant influenza A virus expressing an NS1 defective in its ability to bind and inhibit TRIM25 is attenuated and induces more IFN than wild type virus. In our proposed project, we will now investigate in detail the mechanism of inhibition of TRIM25 by the NS1 protein and the functional consequences of this inhibition on the host antiviral response and in the pathogenicity of influenza A virus. Since the NS1 protein has a complex set of nuclear import and export signals regulating its intracellular localization, we will also investigate the relationship between NS1 localization and function, and how NS1 localization is regulated during viral infection. Trafficking studies of NS1 in the cell will be performed with the help of the Imaging Core. These studies will provide us with a better understanding of the suppression of type I IFN induction by influenza virus. Our project will be complemented by Projects 1 and 3, that study the opposite side of the virus-host IFN response, i.e. induction of RIG-I activation;Project 2, that will provide us with structural clues on how RIG-I can be activated/inhibited;and Project 4, that study the impact of a different RNA virus, hepatitis C virus, in the host response, allowing us to compare different mechanisms used by two viruses to evade innate immunity.

Public Health Relevance

Influenza virus is a relevant pathogen that causes significant mortality and morbidity in humans. The NS1 protein of this virus is an important virulence factor responsible for evasion of the host antiviral response. Our studies will shed light on the mechanism how the NS1 protein allows influenza virus to avoid cellular recognition and triggering of the antiviral response, an important feature associated with virulence.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Program--Cooperative Agreements (U19)
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Special Emphasis Panel (ZAI1-BDP-I)
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University of Southern California
Los Angeles
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Rajsbaum, Ricardo; Garcia-Sastre, Adolfo; Versteeg, Gijs A (2014) TRIMmunity: the roles of the TRIM E3-ubiquitin ligase family in innate antiviral immunity. J Mol Biol 426:1265-84
Shi, Mude; Cho, Hyelim; Inn, Kyung-Soo et al. (2014) Negative regulation of NF-?B activity by brain-specific TRIpartite Motif protein 9. Nat Commun 5:4820
Peterson, Joseph R; Labhsetwar, Piyush; Ellermeier, Jeremy R et al. (2014) Towards a computational model of a methane producing archaeum. Archaea 2014:898453
Runge, Simon; Sparrer, Konstantin M J; Lässig, Charlotte et al. (2014) In vivo ligands of MDA5 and RIG-I in measles virus-infected cells. PLoS Pathog 10:e1004081
Deimling, Tobias; Cui, Sheng; Lammens, Katja et al. (2014) Crystal and solution structure of the human RIG-I SF2 domain. Acta Crystallogr F Struct Biol Commun 70:1027-31
Santiago, Felix W; Covaleda, Lina M; Sanchez-Aparicio, Maria T et al. (2014) Hijacking of RIG-I signaling proteins into virus-induced cytoplasmic structures correlates with the inhibition of type I interferon responses. J Virol 88:4572-85
Rajsbaum, Ricardo; Versteeg, Gijs A; Schmid, Sonja et al. (2014) Unanchored K48-linked polyubiquitin synthesized by the E3-ubiquitin ligase TRIM6 stimulates the interferon-IKK? kinase-mediated antiviral response. Immunity 40:880-95
Ayllon, Juan; Domingues, Patricia; Rajsbaum, Ricardo et al. (2014) A single amino acid substitution in the novel H7N9 influenza A virus NS1 protein increases CPSF30 binding and virulence. J Virol 88:12146-51
Roth, Susanne; Rottach, Andrea; Lotz-Havla, Amelie S et al. (2014) Rad50-CARD9 interactions link cytosolic DNA sensing to IL-1? production. Nat Immunol 15:538-45
Pulloor, Niyas Kudukkil; Nair, Sajith; McCaffrey, Kathleen et al. (2014) Human genome-wide RNAi screen identifies an essential role for inositol pyrophosphates in Type-I interferon response. PLoS Pathog 10:e1003981

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