Increased Mistranslation ProtectsE. colifrom Protein Misfolding Stress due to Activation of a RpoS-dependent Heat Shock Response

The misincorporation of an incorrect amino acid into a polypeptide during protein synthesis is considered a detrimental phenomenon. Mistranslated protein is often misfolded and degraded or non-functional and results in an increased cost to quality control machinery. Despite these costs, errors during protein synthesis are common in bacteria. Here we report that increased rates of mistranslation in Escherichia coli provide protection from protein misfolding stress by increasing the level of the heat shock sigma factor, RpoH. Surprisingly, this increase in RpoH due to mistranslation is dependent on the presence of the general stress response sigma factor, RpoS. This report provides evidence for a protective function of mistranslation and suggests a novel regulatory role of RpoS on the RpoH-activated heat shock.