Apr 20, 2020

Escherichia coli small heat shock protein IbpA is an aggregation-sensor that self-regulates its own expression at a translational level

BioRxiv : the Preprint Server for Biology
Hideki TaguchiY. Chadani


Aggregation is an inherent characteristic of proteins. Risk management strategies to reduce aggregation are critical for cells to survive upon stresses that induce aggregation. Cells cope with protein aggregation by utilizing a variety of chaperones, as exemplified by heat-shock proteins (Hsps). The heat stress-induced expression of IbpA and IbpB, small Hsps in Escherichia coli, is regulated by the {sigma}32 heat-shock transcriptional regulator and the temperature-dependent translational regulation via mRNA heat fluctuation. We found that, even without heat stress, either the expression of aggregation-prone proteins or the ibpA gene deletion profoundly increases the expression of IbpA. Combined with other evidence, we propose novel mechanisms for the regulation of the small Hsp expression. Oligomeric IbpA self-represses the ibpA/ibpB expression at the translational level, but the self-repression is relieved by the sequestration of IbpA into protein aggregates. Thus, the function of IbpA as a chaperone to form co-aggregates is harnessed as an aggregation sensor to tightly regulate the IbpA level. Since the excessive preemptive supply of IbpA in advance of stress is harmful, the prodigious and rapid expression of IbpA/IbpB on dem...Continue Reading

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