<i>Escherichia coli</i> small heat shock protein IbpA plays a role in regulating the heat shock response by controlling the translation of σ³².

Abstract

Small heat shock proteins (sHsps) act as ATP-independent chaperones that prevent irreversible aggregate formation by sequestering denatured proteins. IbpA, an <i>Escherichia coli</i> sHsp, functions not only as a chaperone but also as a suppressor of its own expression through posttranscriptional regulation, contributing to negative feedback regulation. IbpA also regulates the expression of its paralog, IbpB, in a similar manner, but the extent to which IbpA regulates other protein expressions is unclear. We have identified that IbpA down-regulates the expression of many Hsps by repressing the translation of the heat shock transcription factor σ³². The IbpA regulation not only controls the σ³² level but also contributes to the shutoff of the heat shock response. These results revealed an unexplored role of IbpA to regulate heat shock response at a translational level, which adds an alternative layer for tightly controlled and rapid expression of σ³² on demand.