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.

The dnaX gene of many bacteria yields two DNA polymerase subunits in a 1:1 ratio. The longer product tau ( ) has essentially all the sequence of the shorter gamma (␥ ), but a C-terminal extension that comprises about one-third of its length encompasses additional functional domains. In Caulobacter crescentus, ␥ is essential and derives from proteolytic cleavage of the longer (317). In E. coli, after considerable controversy, it has recently been established that ␥ is part of the DNA polymerase III holoenzyme complex and is important for UV resistance and normal functioning of Pol IV mutagenesis associated with double strand-break repair (318). In a counterpart to the yeast prion [PSI]+ considered above and below, error-prone polymerases are important for generating mutations for evolutionary fitness (319). Consistent with significance of ␥ is a diversity of mechanisms for its generation and these are considered next.