%0 Journal Article %T Mechanism of trans-translation revealed by in vitro studies %A Hyouta Himeno %A Akira Muto %J Frontiers in Microbiology %D 2014 %I Frontiers Media %R 10.3389/fmicb.2014.00065 %X tmRNA is a bacterial small RNA having a structure resembling the upper half of tRNA and its 3¡ä end accepts alanine followed by binding to EF-Tu like tRNA. Instead of lacking a lower half of the cloverleaf structure including the anticodon, tmRNA has a short coding sequence for tag-peptide that serves as a target of cellular proteases. An elaborate coordination of two functions as tRNA and mRNA facilitates an irregular translation termed trans-translation: a single polypeptide is synthesized from two mRNA molecules. It allows resumption of translation stalled on a truncated mRNA, producing a chimeric polypeptide comprising the C-terminally truncated polypeptide derived from truncated mRNA and the C-terminal tag-peptide encoded by tmRNA. Trans-translation promotes recycling of the stalled ribosomes in the cell, and the resulting C-terminally tagged polypeptide is preferentially degraded by cellular proteases. Biochemical studies using in vitro trans-translation systems together with structural studies have unveiled the molecular mechanism of trans-translation, during which the upper and lower halves of tRNA are mimicked by the tRNA-like structure of tmRNA and a tmRNA-specific binding protein called SmpB, respectively. They mimic not only the tRNA structure but also its behavior perhaps at every step of the trans-translation process in the ribosome. Furthermore, the C-terminal tail of SmpB, which is unstructured in solution, occupies the mRNA path in the ribosome to play a crucial role in trans-translation, addressing how tmRNA¡€SmpB recognizes the ribosome stalled on a truncated mRNA. %K trans-translation %K tmRNA %K SmpB %K ribosome rescue system %K molecular mimicry %U http://www.frontiersin.org/Journal/10.3389/fmicb.2014.00065/abstract