RNA-dependent solubility of Escherichia coli proteome: Structural hub, disorder, and chaperone network

Protein aggregation is a complex phenomenon involving aberrant folding and proteostasis that leads to various proteopathies. Despite extensive efforts, the maintenance of protein solubility against aggregation remains ill-defined, especially in complex cellular environments. In this study, we show that the depletion of RNAs from Escherichia coli lysates results in global protein aggregation. Using quantitative mass spectroscopic analysis, we identified significant proteins (>900) from the whole E. coli proteome whose solubility maintenance is dependent on RNA. Proteome-wide characterization revealed that RNA dependence was highly enriched among acidic proteins, intrinsically disordered proteins, and structural hub proteins. Notably, the solubility of representative molecular chaperones [Trigger factor (TF), DnaJ, and GroES] is largely dependent on RNA, suggesting a hitherto unknown hierarchical relationship between RNA-based chaperone (chaperna) and protein-based molecular chaperones. Our findings provide new insights into proteome solubility maintenance and misfolding-associated proteopathy in vivo, where proteins, from birth to death, stably or transiently associate with RNAs.