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.

Frameshifting is independently utilized to synthesize a proportion of the C-terminal immunoglobin-like domains present in diverse phages on different proteins (148, 149) . An occurrence of this type of frameshifting to yield an extension of the major coat protein of phage T3 results in two products from one gene in the viral capsid (150) . Cu-riously the counterpart extension in the close relative phage T7 (74, 151, 152) is not an Ig-like domain. With phage T3, and others such as Lactobacillus phage A2 (145, 146) , the Ig-like extension derives from −1 frameshifting. With Listeria phages A118 and A500 −1 frameshifting also occurs in decoding a coat protein gene, though in phage PSA it is +1 ( Figure 3D ). In all 3 phages additionally +1 frameshifting is utilized to derive a second product from the major tail protein gene (153, 154) . Apparent indifference to whether the frameshifting is +1 or −1, or even whether frameshifting is involved to yield the Ig-like extension instead of inframe decoding, has reasonably been suggested to reflect chance. Dynamic movement of Ig-like domains via nonhomologous recombination would land some in-frame and some out-of-frame with selection for function in the latter cases sometimes resulting in expression via frameshifting (155) .