The sumoylation of the non-structural protein 1 of the influenza a virus plays a dual role during viral infection
The potential for a highly pathogenic influenza pandemic remains a concern for global health. The ability of the influenza virus to undergo antigenic shift and genetic drift give circulating strains of influenza the high probability of developing resistance to current antiviral therapies. Emerging strains of higher virulence, to which the infected person has not had any previous exposure to viral antigens, pose a greater threat of serious illness and death. Currently, there is no antiviral therapy that is effective against all strains of influenza, emphasizing the need to develop new strategies that target cellular systems required for viral replication to combat influenza. Our laboratory recently identified global increases in cellular SUMOylation as a consequence of influenza infection. Remarkably, influenza caused these increases in SUMO conjugation independent of changes in the levels of the key enzymes involved in the SUMO pathway, such as SENP1, SAE1, SAE2, and Ubc9. Although our studies have concluded that the increase in cellular SUMOylation is interferon-independent and constitutes a shared characteristic amongst all viral strains examined to date, the main viral factor responsible for triggering this increase in the SUMO profile remains unresolved. For this purpose, we identified the non-structural protein 1, NS1, as the main viral factor involved in triggering the increases in cellular SUMOylation. Additionally, we attributed NS1's ability to govern these increases in cellular SUMOylation as independent of its RNA-binding ability and dependent on its ability to be post-translationally modified by the SUMO protein. Besides influenza's ability to affect global SUMO conjugation, most of the influenza viral proteins were observed to be post-translationally modified by SUMO, including the NS1 protein. Given that the functionality of SUMOylation has been proposed for the SUMOylation of NS1 by other groups, much evidence, including data produced in our laboratory, contradicts the suggested function. Therefore, we further evaluated the molecular effects of SUMO conjugation on NS1's role in regulating viral protein synthesis. We found that although SUMOylation does not play a role in governing the stability of NS1, it affects NS1's ability to regulate viral protein synthesis during viral infection, a functionality that is mainly dependent on NS1's RNA-binding ability. Lastly, the NS1 viral protein is involved in numerous cellular and viral protein-protein interactions during the viral life cycle. The Artificial SUMO-Ligase was developed as a tool that specifically increases the SUMOylation of NS1, therefore allowing us to establish a better understanding of the effects of SUMOylation on NS1. We further characterized the relationship between the Artificial SUMO-Ligase and NS1 by identifying the Artificial SUMO-Ligase as a NS1-interacting protein by Co-immunoprecipitation using a reversible cross-linker. Altogether, we have identified a dual role for NS1 SUMOylation during viral infection and have identified the Artificial SUMO-Ligase as an NS1-interacting protein. Further characterization of the virus-SUMO interactions may lead to novel insights on how influenza benefits from SUMOylation, while also largely contributing to the development of novel therapies that inhibit viral replication by targeting indispensable cellular systems utilized by influenza.
Chacon, Jason Michael, "The sumoylation of the non-structural protein 1 of the influenza a virus plays a dual role during viral infection" (2014). ETD Collection for University of Texas, El Paso. AAI3636249.