Exploring Flavivirus NS3 and NS5 Interfaces Required for RNA Replication and Capping

Mosquito-borne flaviviruses, including Zika virus (ZIKV) and dengue virus, pose a major public health concern. Currently, there are no antiviral therapies available against any flavivirus. The development of flavivirus therapeutics has been focused on inhibiting the function of the viral replicase complex, which is essential for successful viral replication. During viral replication, the replicase complex is responsible for replicating the viral ribonucleic acid (RNA) genome, a prerequisite for the production of progeny viruses. Additionally, the replicase complex adds a cap structure onto the newly-synthesized viral genome, thereby making the genome competent to produce viral proteins. While it is known that the replicase complex is made up of two viral proteins, known as nonstructural (NS) proteins 3 and 5, the overall structure and organization of the viral replicase complex remains unclear. Preliminary findings in the Sagan Lab have revealed the basic organization of the ZIKV replicase complex and identified two novel protein interfaces between the NS3 and NS5 proteins within the complex. The proposed project seeks to evaluate the importance of these two unique NS3-NS5 interfaces for replication and capping of the viral genome. Furthermore, I plan to evaluate whether this replicase complex structure and organization is conserved in other related flaviviruses, such as dengue virus. By providing insight into the structure and organization of the viral replicase complex, this project is likely to reveal novel targets for antiviral intervention. These findings are also likely to be applicable to related flaviviruses, thereby facilitating the development of antiviral therapies against several viruses of public health concern.