Noise buffering by biomolecular condensates in glucose sensing

The Effect of Calorie Restriction on Protein Quality Control in Yeast

Initially, protein aggregates were regarded as a sign of a pathological state of the cell. Later, it was found that these assemblies are formed in response to stress, and that some of them serve as signalling mechanisms. This review has a particular focus on how intracellular protein aggregates are related to altered metabolism caused by different glucose concentrations in the extracellular environment. We summarise the current knowledge of the role of energy homeostasis signalling pathways in the consequent effect on intracellular protein aggregate accumulation and removal. This covers regulation at different levels, including elevated protein degradation and proteasome activity mediated by the Hxk2 protein, the enhanced ubiquitination of aberrant proteins through Torc1/Sch9 and Msn2/Whi2, and the activation of autophagy mediated through ATG genes. Finally, certain proteins form reversible biomolecular aggregates in response to stress and reduced glucose levels, which are used as a signalling mechanism in the cell, controlling major primary energy pathways related to glucose sensing.

RNA chain length and stoichiometry govern surface tension and stability of protein-RNA condensates

Proteomic studies have shown that cellular condensates are frequently enriched in diverse RNA molecules, which is suggestive of mechanistic links between phase separation and transcriptional activities. Here, we report a systematic experimental and computational study of thermodynamic landscapes and interfacial properties of protein-RNA condensates. We have studied the affinity of protein-RNA condensation as a function of variable RNA sequence length and RNA-protein stoichiometry under different ionic environments and external crowding. We have chosen the PolyU sequences for RNA and arginine/glycine-rich intrinsically disordered peptide (RGG) for proteins as a model system of RNA-protein condensates, which we then investigate through in vitro microscopy measurements and coarse-grained molecular dynamics simulations. We find that crowding and RNA chain length can have a major stabilizing effect on the condensation. We also find that the RNA-protein charge ratio is a crucial variable controlling stability, interfacial properties, and the reentrant phase behavior of RGG-RNA mixtures.

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LLPS with long RNAs is favored because of the lower entropic penalty of dissociation

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RNA chain length modulates interfacial and material properties of condensates

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Crowding can stabilize condensates with shorter RNAs

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Salt reduces the reentrant LLPS window but does not change the optimal stoichiometry