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. 2022 Oct 16;50(19):10817–10838. doi: 10.1093/nar/gkac866

Figure 3.

Figure 3.

RNA in biomolecular condensates. (A) A model for the formation of nuclear RNA foci in repeat expansion disorders. Increased RNA valency due to expansion of nucleotide repeat results in RNA gelation and sequestration of RNA molecules into nuclear foci (68). (B) RNA and LLPS in the creation of cellular polar systems. Top: one-cell stage C. elegans embryo. Competition of MEX-5 and PGL-3 proteins for mRNA binding regulates the formation of PGL-3 droplets (81). (C) LLPS-based channeling of ribosomal RNA (rRNA) flux out of the nucleolus. It is proposed that relatively nascent rRNA are available for multiple interactions with scaffolding proteins of the GC-matrix, while rRNA binding with ribosomal proteins decreases their valency, thus disturbing nucleolar LLPS and resulting in the effective emission of fully assembled pre-ribosomal particles (82). (D) Re-entrant liquid condensation. Top: a schematic illustration of three different RNP (ribonucleoprotein complexes):RNA regimes. Bottom: a corresponding phase diagram. The arrow represents the passage of the system from ‘+’ to ‘–’-charged RNPs through a charge-neutral stage and charge inversion when the RNA concentration is increased (RNP concentration is fixed). The shaded area corresponds to the LLPS regime (II). During the condensate dissolution stage, the RNA flux into RNP droplets generates vacuolated coacervates (83).