Coronaviruses: linking polyprotein processing and replication complex function

Coronaviruses are the causative agents of recent human pandemics and common human and animal diseases. Despite their importance, significant details of the coronavirus life cycle remain unknown. Coronaviruses produce the proteins required for genome replication by translating two long polyproteins: pp1a and pp1ab. Two viral proteases process both polyproteins into the components of the viral replication complex. This proteolytic cleavage results in over 100 theoretical fully and partially-cleaved products. The latter are termed 'precursors' and play vital roles in the replication of similar RNA virus families. For the coronaviruses, it has been speculated that early in infection, long partially-cleaved precursors direct antisense RNA synthesis. Late in infection, fully-cleaved polyprotein products direct sense RNA synthesis. However, experimental data and a mechanistic understanding of specific polyprotein cleavage products' roles is lacking. Understanding this process may pave the way for the next generation of antiviral drugs. In this proposal, we will: - Determine: the dynamics and subcellular localization of stable polyprotein precursors across the alpha- beta- and gammacoronaviridae. - Uncover: mechanisms of cellular and viral control of polyprotein dynamics using genetic and inhibitor-based approaches. - Define: the mechanistic function of polyprotein precursors in coronavirus RNA replication.