Figure 5.

Model for tmRNA-mediated translational control in Streptomyces coelicolor. Ribosomes translating mRNAs, such as that of dasR or dnaK, are stalled at the 3′ end, and the first nascent peptide chain becomes tagged for proteolytic degradation. During this tagging process the mRNA is cleaved to remove a yet unknown structural element in the mRNA. As a result, the ribosomes are able to finish translation without further tmRNA tagging. This mechanism allows the instantaneous production of crucial stress proteins after stress. See Discussion section for details. mRNA, messenger RNA; tmRNA, transfer–messenger RNA.