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.

In contrast to transitory decreased termination in bacteria that is alleviated by regulatory frameshifting, there may be a permanent counterpart in the ciliate Euplotes (for image see (813)). Studies of specific individual Euplotes genes have revealed many where frameshifting is involved in expression, including protein kinases (34,35,358) and the telomerase components described above (31). In Euplotes, UGA is reassigned from being a stop codon, perhaps derived by selection as a defence against invading pathogens including in their food (359) . It has been proposed that the accompanying alteration of release factor recognition (360) results in poor decoding of UAA (in the ribosomal A-site) thereby enhancing the opportunity for frameshifting when the P-site tRNA has potential for re-pairing in the +1 frame (361, 362) . Though this is likely relevant, rampant frameshifting is not known in ciliates other than Euplotes even though they also feature stop codon reassignment (of UAG in some). Intriguing mysteries abound and the discovery that WT release factor can be involved in 4-base stop codon recognition may be relevant (363, 364) .