RNA is a critical element for the sizing and the composition of phase-separated RNA–protein condensates

Abstract

Liquid–liquid phase separation is thought to be a key organizing principle in eukaryotic cells to generate highly concentrated dynamic assemblies, such as the RNP granules. Numerous in vitro approaches have validated this model, yet a missing aspect is to take into consideration the complex molecular mixture and promiscuous interactions found in vivo. Here we report the versatile scaffold ArtiG to generate concentration-dependent RNA–protein condensates within living cells, as a bottom-up approach to study the impact of co-segregated endogenous components on phase separation. We demonstrate that intracellular RNA seeds the nucleation of the condensates, as it provides molecular cues to locally coordinate the formation of endogenous high-order RNP assemblies. Interestingly, the co-segregation of intracellular components ultimately impacts the size of the phase-separated condensates. Thus, RNA arises as an architectural element that can influence the composition and the morphological outcome of the condensate phases in an intracellular context.

The involvement of stress granules in aging and aging‐associated diseases

“…Thus, for assemblies like SGs, which contain a high local concentration of RNA molecules, RNA‐RNA interactions and RNA structure seem to be general features of importance for their formation. Detailed information about the roles of RNA in forming SGs and other RNP granules can be found in recent reviews (Garcia‐Jove Navarro et al, 2019; Van Treeck & Parker, 2018).…”

Dietary Gluten and Neurodegeneration: A Case for Preclinical Studies

“…While BMCs assemble by thermodynamic-mediated liquid-liquid phase separation, the liquid BMCs are known to transform into reversible amyloid fibers or insoluble aggregates [70]. While the details of BMC biology is still evolving, it has been shown that RNA and proteins with intrinsically disordered regions are key factors that influence the intracellular composition, size, and morphology of BMCs [71,72]. Unlike BMCs, EVs contain at least one membrane.…”

Granule regulation by phase separation during Drosophila oogenesis

“…Our understanding of the biophysical and biochemical principles that govern granule diversity, assembly and disassembly has recently benefited from new conceptual frameworks. LLPS has emerged as an attractive model to explain the observed properties of membrane-less organelles, including RNP granules [11,48,[80][81][82][83]. The earliest example of maternal RNP structures shown to exhibit liquid-like behaviour were induced 'bodies' found in the Drosophila oocyte nucleus.…”

“…RNA storage and translational control is likely a major function of RNP granules in oogenesis as they form in response to high levels of untranslated mRNAs and disperse at a time when many mRNAs are translated. While proteins are typically considered to be the key scaffolds for granule assembly, more recently RNA has also been shown to both phase separate and drive the assembly of RNP condensates [80,83,107,108].…”

“…These observations suggest a model whereby 'sticky' mRNAs promote granule nucleation by concentrating key scaffold proteins through sequence specific binding and subsequently regulate stability and material property. Testing this model in vivo requires developing techniques to selectively disrupt mRNAs while observing the effect on the RNP granules [80]. Complementarily, in vitro transcribed RNAs could be used in combination with specific scaffold proteins to reconstitute RNP granules.…”