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. Author manuscript; available in PMC: 2021 Apr 1.
Published in final edited form as: Nat Rev Mol Cell Biol. 2020 Jul 6;22(3):183–195. doi: 10.1038/s41580-020-0264-6

Figure 4: Balancing RNA and protein ratios in condensates.

Figure 4:

(A and B) RNA with high valency (A) refers to an RNA molecule that contains multiple sequences and/or structures (grey triangles) that can be recognized by an RNA-binding protein (RBP). Low valency (B) refers to an RNA with few such sequences or structures. High valency may favor liquid–liquid phase separation (LLPS) over low valency. A fraction, or all of the potential binding sites for RBPs could be actually bound by RBPs (blue triangles), resulting in unsaturated (C) or saturated (D) RNA to protein ratios, respectively. Saturation may favor LLPS. (E) A possible phase diagram of a mixture of RNA and protein at a particular temperature. Phase separation between the RNA and protein occurs within the parameters of the purple ellipsoid and is a factor of the concentrations of RNA, of protein, and of buffer (not shown). (F) Increasing the valency of the RNA target may shift the phase diagram to the right (red ellipse), indicating that a lower RNA concentration is required to induce LLPS. (G) Reducing RNA valency may have an opposite effect.