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.

Especially interesting for two reasons is an analysis of dogs of different breeds with poly(A) inserts in a gene essential for vision, as it illustrates the potential for iterative effects at multiple levels in gene expression. With an insert giving a poly(A) tract of 28 As the overall total of shifting to the +1 frame with respect to the genomic sequence is 40% (382) . Identification of a modifier that has a big effect on the level of frameshifting (383) should be informative. In addition to the long known ribosomal frameshifting on runs of A to an alternative frame, realignment by −3 has recently been described to yield a zero-frame product with an extra lysine (384) . There is just a single AAA AAA AAA sequence in E. coli coding sequence (50-fold less common than extrapolated from the number of AAA codons) [Where ribosomal frameshifting to the +1 frame occurs by shifting either −2 or +1 nt, the frameshift product of the former has an extra amino acid compared to the latter. Retrograde realignment (toward the mRNA 5 end) has also been demonstrated with a cassette with a derivative of the T4 gene 60 bypassing sequence region; in that case, with coding resumption occurring in a different frame so that one ribosome decoded a sequence segment and, following transient peptidyl-tRNA anticodon: codon dissociation, realigned backwards to read the same sequence in a different frame to synthesize a single product (385) .]