Abstract
Programmed -1 ribosomal frameshifting (-1PRF) is an mRNA recoding event commonly utilized by viruses and bacteria to increase the information content of their genomes. Recent results have implicated -1PRF in quality control of mRNA and DNA stability in eukaryotes. Biophysical experiments demonstrated that the ribosome changes the reading frame while attempting to move over a slippery sequence of the mRNA--when a roadblock formed by a folded downstream segment in the mRNA stalls the ribosome in a metastable conformational state. The efficiency of -1PRF is modulated not only by cis-regulatory elements in the mRNA but also by trans-acting factors such as proteins, miRNAs, and antibiotics. These recent results suggest a molecular mechanism and new important cellular roles for -1PRF.