Regulatory implications of translational frameshifting in cellular gene expression

The genetic code, once thought to be rigid, has been found to be quite flexible, permitting several different reading alternatives. One of these is translational frameshifting, a process programmed in the mRNA sequence and which enables a +1 or -1 shift from the reading frame of the initiation codon. So far, the involvement of translational frameshifting in gene expression has been described mainly in viruses (particularly retroviruses), retrotransposons, and bacterial insertion elements. In this MicroReview, we present a survey of the cellular genes, mostly in Escherichia coli, which have been found to be expressed through a translational frameshifting process, as well as a discussion of the regulatory implications of this process.