Does 2A-mediated stop codon-independent termination of translation predominateover start codon-independent re-initiation of translation under conditions of translational 'stress' ? (360G-Wellcome-077228_Z_05_A)

The oligopeptide 2A sequence (just 18aa) mediates a co-translational 'cleavage'. When ribosomes encounter 2A, two outcomes ensue. Either (i) translation terminates in a stop codon-independent manner, or, (ii) translation of a specific (glycyl-prolyl) peptide bond is 'skipped' and translation, in effect, re-initiates to synthesis downstream sequences. We propose that this method of protein biogenesis confers the ability to preferntially translate only one part of an open reading frame under conditinos of translational 'stress'. At latter stages of infection this system could direct the remaining cellular resources into translating sequences upstream of 2A (capsid proteins), rather than those downstream (replication proteins). In this manner, the yeild of progeny virions could be enhanced. '2A-like' sequences are found in a very wide range of pathogens and 2A is used extensively in biomedical and biotechnological applications. Our findings will help interpret the role of 2A-like sequences in these other systems and underpin its use in biotechnology. The key goals of the project are twofold; (i) to build a kinetic scheme of protein biogenesis of TME to determine if more capsid, than replication, proteins are made duringinfection, and (ii) to identify what aspect of the translational machinery is determining the outcome of 2A- mediated 'cleavage'.