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.

Recently a natural stem loop structure 4 nts 5 of the SARS coronavirus −1 frameshift site was reported to attenuate the −1 frameshifting level involved but to be able to stimulate +1 frameshifting in tests with synthetic constructs (504) . It is mimicable by a paired antisense oligo (505) . However, its functioning is still mysterious. An inhibitory stem loop has also been reported for pea enation mosaic virus frameshifting (406) . Earlier the effect of inserting a palindromic sequence that could form a stem loop structure was tested on feline immunodeficiency virus frameshifting (506) . To what extent inhibitors serve to link ribosome loading to Figure 12 . The features of release factor 2 autoregulatory frameshifting are highly conserved in diverse bacteria. The level of the release factor for the underlined ORF1 stop codon UGA(C) governs the efficiency with which the anticodon paired to the 5 adjacent codon, CUU, shifts +1 to pair with UUU permitting continued translation to synthesize release factor 2. The frameshift stimulatory internal Shine Dalgarno (SD) sequence is preceeded by sequence unable to pair with the anti-Shine Dalgarno sequence of translating ribosomes, permitting availability of the anti-Shine Dalgarno to form the correctly positioned frameshift stimulatory hybrid with mRNA. The figure was generated with Weblogo3 (815) using RF2 frameshift sites obtained from ARFA (348). frameshifting efficiency, and for virus infection potentially with phase of the infective cycle, remains to be seen.