Unveiling the Polymerase Complex of Negative Stranded RNA Viruses

Negative stranded RNA viruses (NSVs) are among the most common human pathogens which cause pandemics and epidemics. This group includes many notable members such as influenza, mumps and Ebola viruses. These viruses are identifiable by their negative polarity genome which is associated with the nucleocapsid (NP) protein and assembled into higher order structures. The RNA-nucleocapsid complex or ribonucleoprotein (RNP) serves as the template for transcription and replication by the viral RNA-dependent RNA polymerase (vRdRp). Though progress has been made in the study of these viruses, knowledge is lacking with regards to the polymerase complex. Here, we utilize structural biology and mutational analysis to identify components of the polymerase complex that will be targets for drug design. NSVs typically cause high mortality outbreaks by transmission from animal reservoirs. In fact, in 2013 H7N9 avian influenza A virus emerged as human infections and in 2017 the number of infections raised to 688. This reaffirms that influenza virus is a global health threat and requires antiviral drugs in the effort to control influenza virus. Frequently used anti-influenza drugs target neuraminidase; however, there have been strains that show resistance to these neuraminidase inhibitors. The PB2cap binding domain of the influenza RNA polymerase is an innovative target for development of anti-influenza drugs. In this study, we have solved the crystal structure of the PB2cap binding domain of influenza A H1N1 virus alone and in complex with its binding partner. Utilizing this structure, we have identified critical interactions that will aid in the design of antivirals. The emergence of mumps virus outbreaks throughout the United States in the past five years indicates that the MMR vaccine is not the most efficient source of protection and reaffirms the need for inhibitors that target the virus.Here, we have utilized cryogenic electron microscopy (cryoEM) to analyze the RNA encapsidation of mumps virus nucleocapsid and mutational analysis of the phosphoprotein to probe the interactions involved in uncoiling the nucleocapsid. This data adds to the available knowledge about mumps virus infection and could potentially aid in the design of inhibitors