Cell 2023, Online Sep 12. doi: 10.1016/j.cell.2023.08.018
Self-demixing of mRNA copies buffers mRNA:mRNA and mRNA:regulator stoichiometries
Andrés H. Cardona1,4, Szilvia Ecsedi1,4, Mokrane Khier1, Zhou Yi1, Alia Bahri1, Amira Ouertani1, Florian Valero1, Margaux Labrosse1, Sami Rouquet1, Stéphane Robert2, Agnes Loubat1, Danielle Adekunle3, Arnaud Hubstenberger1,5
1Université Côte d’Azur, CNRS, Inserm, iBV, Nice, France.
2Université Aix Marseille, Inserm, INRAE, C2VN, 13005 Marseille, France.
3Université Côte D’Azur, CNRS, Inserm, IRCAN, 06107 Nice, France.
4These authors contributed equally
Cellular homeostasis requires the robust control of biomolecule concentrations, but how do millions of mRNAs coordinate their stoichiometries in the face of dynamic translational changes? Here, we identified a two-tiered mechanism controlling mRNA:mRNA and mRNA:protein stoichiometries where mRNAs super-assemble into condensates with buffering capacity and sorting selectivity through phase transition mechanisms. Using C. elegans oogenesis arrest as a model, we investigated the transcriptome cytosolic reorganization through the sequencing of RNA super-assemblies coupled with single mRNA imaging. Tightly repressed mRNAs self-assembled into same-sequence nanoclusters that further co-assembled into multiphase condensates. mRNA self-sorting was concentration-dependent, providing a self-buffering mechanism that is selective to sequence identity and controls mRNA:mRNA stoichiometries. The cooperative sharing of limiting translation repressors between clustered mRNAs prevented the disruption of mRNA:repressor stoichiometries in the cytosol. Robust control of mRNA:mRNA and mRNA:protein stoichiometries emerges from mRNA self-demixing and cooperative super- assembly into multiphase multiscale condensates with dynamic storage capacity.