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 σ³² 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 Hsps expression. Oligomeric IbpA self‐represses the ibpA/ibpB translation, and mediates its own mRNA degradation, but the self‐repression is relieved by sequestration of IbpA into the 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 demand is necessary for IbpA to function as a first line of defense against acute protein aggregation.

中文翻译：

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大肠杆菌小热休克蛋白 IbpA 是一种聚集传感器，可在转录后水平自我调节自身表达

聚集是蛋白质的固有特性。减少聚集的风险管理策略对于细胞在诱导聚集的压力下存活至关重要。细胞通过利用各种分子伴侣来应对蛋白质聚集，例如热休克蛋白 (Hsps)。热应激诱导的大肠杆菌中小热蛋白 IbpA 和 IbpB 的表达受σ ³²热休克转录调节因子和通过 mRNA 热波动的温度依赖性翻译调节的调节。我们发现，即使没有热应激，易聚集蛋白或ibpA 的表达基因缺失极大地增加了 IbpA 的表达。结合其他证据，我们提出了调节小 Hsps 表达的新机制。寡聚 IbpA 自我抑制ibpA/ibpB翻译，并介导其自身的 mRNA 降解，但通过将 IbpA 隔离到蛋白质聚集体中可以缓解自我抑制。因此，IbpA 作为形成共聚集体的分子伴侣的功能被用作聚集传感器来严格调节 IbpA 水平。由于 IbpA 在压力之前的过度抢先供应是有害的，因此 IbpA/IbpB 按需大量快速表达对于 IbpA 作为抵御急性蛋白质聚集的第一道防线是必要的。