MinD-RNase E interplay controls localization of polar mRNAs in E. coli

We have recently shown that the polar transcriptome of E. coli is unique compared to the membrane and cytosolic ones. Several factors were suggested to mediate mRNA localization to the membrane, but the mechanism of localizing mRNAs to the poles is not known. We combined a candidate system approach with high-throughput proteomics to identify factors that mediate polar mRNAs localization. We identified MinD as an essential factor in this process, whose binding to RNAs is indirect. We demonstrate that RNase E, previously shown to interact with MinD, is also required for proper localization of polar mRNAs. Using in silico modeling followed by experimental validation, the membrane-binding site in RNase E was found to mediate binding to MinD. Intriguingly, not only does MinD affect RNase E interaction with the membrane, but it also affects its mode of action and dynamics. Polar accumulation of RNase E in ΔminCDE cells resulted in destabilization and depletion of mRNAs from the poles. Finally, we show that mislocalization of polar mRNAs may prevent polar localization of their protein products. Taken together, MinD and RNase E are assigned novel roles, whereas the interplay between them determines the composition of the polar transcriptome, thus affecting the polar proteome.