Reassessing the tmRNA-SmpB complex as a virulence determinant

Rescuing stalled ribosomes from the truncated mRNA is identified as a crucial process for the survival of a bacterial cell. A small RNA named tmRNA (transfer messenger RNA), and protein SmpB (Small protein B), together constitute a ribosome rescue apparatus which is ubiquitous among most of the eubacteria. tmRNA mediated ribosome rescue process (also called trans-translation) has been found to be the major pathway of clearance of stalled ribosome complexes. In the process, tmRNA-SmpB complex recycles stalled ribosomes by making them undergo normal translation and termination. Apart from rescuing stalled ribosomes, trans-translation modulates other cellular pathways (such as cell cycle, oxidative stress, nutritional stress, DNA damage response and so on) by regulating the intracellular level of various proteins. It becomes more and more obvious that the function of trans-translation apparatus is diverse and plays a role in bacterial pathogenesis also. This review will focus on the key findings on the involvement of tmRNA and its partner SmpB in regulation of pathogenesis and virulence in different pathogenic bacteria.