Pathogenic RNA viruses pose a great threat to human health. Apart from the current COVID-19 pandemic, many other RNA virus outbreaks have occurred in the last 20 years (SARS-CoV, MERS-CoV, Ebola, amongst others), several of which are still ongoing. The constant emergence of RNA virus pathogens requires the development of modular therapeutic discovery platforms that can be quickly adapted to the emerging virus. One way this can be achieved is by taking advantage of conserved mechanisms in RNA viruses. Antivirals targeting conserved replication machinery such as RNA-dependent RNA polymerase (RdRP) have proven to be very successful and broadly applicable. However, this requires a molecular understanding of the viral genome encoded enzymes involved in these processes. My research project aims to develop in vivo phenotypic platforms for studying enzymes involved in the essential and highly conserved, but less explored, step in RNA virus replication: capping of the viral RNA genome.