Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use

Atkins, John F.; Loughran, Gary; Bhatt, Pramod R.; Firth, Andrew E.; Baranov, Pavel V.

Though viruses are not known to encode their own ribosomes, they are masters at customizing their host's translation machinery to optimize their own gene expression. Increasing coding capacity from small genomes with expression occurring in relevant ratios and with appropriate timing, has doubtless contributed to viral utilization of frameshifting. Frameshifting-mediated polyprotein generation involving fusion to capsid components prior to later cleavage, can aid viral packaging of the viral polymerase (e.g. for retroviruses and totiviruses, but not positive-sense single-stranded RNA viruses which don't package their polymerase). Some eukaryotic RNA viruses use polyprotein synthesis, in conjunction with IRES initiation, as part of their strategy to circumvent 5 -end dependence of canonical eukaryotic translation initiation, allowing its inactivation to shut-off host protein synthesis.