Hantaviruses, members of the Bunyaviridae family are enveloped negative strand RNA viruses and category A pathogens that are transmitted to humans through aerosolized excreta of infected rodent hosts. Hantaviruses have evolved a unique translation mechanism for the preferential translation of their mRNAs. This preferential translation is carried out by hantavirus nucleocapsid protein (N-protein) which specifically binds to the mRNA 5' cap and ribosomal protein S19 (RPS19), a structural component of the 40S ribosomal subunit. In addition, a trimeric N-protein molecule specifically binds to a highly conserved triplet repeat sequence (UAGUAGUAG) of the viral mRNA 5' UTR. Our results suggest that N-protein associated ribosomes are selectively loaded on viral mRNA 5' UTR to boost the translation of viral transcripts in the host cell cytoplasm where cellular transcripts are competing for the same translation machinery. Interestingly, our preliminary data shows that N-protein mediated translation strategy also favors the translation of certain host cell factors by an unknown mechanism. Using multifaceted experimental avenues we will determine the mechanism for the selective translation of certain host cell mRNAs by N-protein mediated translation strategy. We will determine whether preferential translation of host cell factors plays a role in virus replication. As antiviral response, host cells transiently shutdown the host translation machinery to create roadblocks for the synthesis of viral proteins. This antiviral response is triggered by the activation of protein kinase R (PKR), which phosphorylates its downstream target eIF2?, causing translational shutdown. Our preliminary results show that N-protein inhibits PKR activation in virus-infected cells to ensure continuous synthesis of viral proteins during the course of infection. We will test the hypothesis that N-protein requires the assistance from endogenous host cell factors to inhibit PKR antiviral response. These studies will reveal new targets for therapeutic intervention of hantavirus disease.
There is no treatment for hantavirus associated disease at present. The major goal of this application is to delineate the mechanism of hantavirus replication in cells. In addition, the proposed studies will help in the identification of new host targets for antiviral drug design.
