Andrés H. Cardona^1,4, Szilvia Ecsedi^1,4, Mokrane Khier¹, Zhou Yi¹, Alia Bahri¹, Amira Ouertani¹, Florian Valero¹, Margaux Labrosse¹, Sami Rouquet¹, Stéphane Robert², Agnes Loubat¹, Danielle Adekunle³, Arnaud Hubstenberger^1,5

Affiliations
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

Abstract

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.

DOI: 10.1016/j.cell.2023.08.018