Structure, mechanism and dynamics of recoding in viral infection

Many RNA viruses (e.g. SARS-CoV-2, HIV-1) have evolved ways of reprogramming translation to expand the coding capacity of their small genomes. ‘Recoding’ events such as -1 frameshifting, stop codon read-through and StopGo peptide release are necessary for viral replication, producing viral proteins in optimal ratios for efficient assembly. Recoding is regulated by a complex interplay between the elongating ribosome, cis-acting elements in the mRNA or nascent peptide, and trans-acting protein factors. Elucidating the structural basis of recoding is essential to understand viral pathogenesis. However, classical biochemical approaches cannot accurately capture kinetics or per-ribosome heterogeneity, making it difficult to define a "window of opportunity" for structure determination. Recent technological advances allow single-molecule fluorescent imaging of translation in real-time. I will apply these methods to study recoding in vitro and in live cells, starting with -1 frameshifting in SARS-CoV-2, HIV-1 and EMCV, which utilise topologically-distinct stimulatory elements. I will determine the structure of key ribosomal states by time-resolved cryo-EM, and investigate the structure and stability of stimulatory elements using crystallography, single molecule FRET and optical tweezers. Longer-term, this approach will be applied to investigate other recoding events, thus revealing universal and case-specific mechanistic principles, and highlighting new avenues for therapeutic intervention.