Résumé
The organization and biophysical properties of the cytoplasm influence all cellular reactions, including molecular interactions and the mobility of biomolecules. The cytoplasm does not behave like a simple fluid but is a densely crowded and highly organized environment. However, its detailed properties, the molecular mechanisms that control them, and how they influence the cellular biochemistry remain poorly understood. Here, we investigate the diffusive properties of the cytoplasm in silico and in vivo, employing mRNPs (messenger ribonucleoproteins) and GEM (genetically encoded multimeric) particles as rheological probes. Cytoplasmic diffusivity increases upon polysome disassembly or a reduction in mRNA levels. Reducing ribosome concentration by up to 20%–25% without altering polysome levels has no effect in vivo. Furthermore, mRNA condensation into P-bodies upon polysome disassembly does not affect cytosolic diffusion in budding yeast. Our results demonstrate that mRNAs and their organization into polysomes regulate the biophysical properties of the eukaryotic cytoplasm.
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•Polysomes and mRNA regulate the biophysical properties of the cytoplasm•The mobility of mRNPs and GEM particles increases upon polysome disassembly•Perturbation of mRNA levels leads to enhanced cytosolic diffusion
Gade et al. report that polysomes and mRNA levels impact the biophysical properties of the cytoplasm. Using passive rheology probes and single-particle tracking, they demonstrate that intracellular diffusion is enhanced when polysomes are disassembled or when mRNA levels are reduced in eukaryotic cells.