Escherichia coli small heat shock protein IbpA plays a role in regulating the heat shock response by controlling the translation of σ ³²

Abstract

Small heat shock proteins (sHsps) act as ATP-independent chaperones that prevent irreversible aggregate formation by sequestering denatured proteins. IbpA, an Escherichia coli 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 σ 32 . The IbpA regulation not only controls the σ 32 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 σ 32 on demand.

The mRNA binding-mediated self-regulatory function of small heat shock protein IbpA in γ-proteobacteria is conferred by a conserved arginine

“…The nonconventional function of IbpA Ec as an aggregation-sensor tightly suppresses IbpA Ec expression under aggregation-free conditions but enables cells to rapidly upregulate the IbpA Ec levels upon acute aggregation stress, such as heat shock ( 10 , 18 ). Moreover, a recent study has demonstrated that IbpA Ec also downregulates the expression of other Hsps by inhibiting the translation level of the heat shock transcription factor σ 32 , which highlights the general importance of IbpA in the heat shock response regulation ( 19 ).…”