The study of the spatial organization of mRNAs encoding for protein complex subunits in the cytosol

The majority of cellular proteins need to fold as part of a complex in order to function. Despite the prevalence of protein complexes, the mechanisms ensuring the formation of specific protein-protein interfaces in the crowded environment of the cell remain obscure. Recent work from our lab revealed a prevalent mechanism for subunits association; during translation, nascent subunits are frequently engaged by their complex partner subunits. Co-translational assembly interactions protect misfolding prone subunits from aggregation. However, the key question of whether mRNAs are spatially organized to facilitate complex assembly remains largely obscure. For this purpose, we follow mRNAs encoding for various subunits of the same complex by single-molecule Fluorescence in situ Hybridization (smFISH). We use yeast and U2OS human osteosarcoma cell line. We compare the level of co-localization of mRNAs encoding for subunits of the same complex to mRNAs encoding for subunits from two different complexes. Next, we characterize the mRNA assemblies by super-resolution imaging and quantify their number and distribution in the cell. Utilizing these approaches, we found mRNAs encoding for various subunits of the same complex co-localize in the cytosol and we are investigating localization mechanisms associated with the co-translational assembly. Together, our research provides crucial mechanistic insights on protein synthesis, folding, and association pathways, opening new horizons for the therapy of aberrant protein assemblies, characteristic of numerous conformational diseases.