Fig. 2. Multivalency-driven phase separation of cellular bodies.

Most cellular bodies are considered to be phase-separated liquid droplets. Liquid-liquid phase separation is driven by multivalent architectural molecules. Such multivalent interactions can be provided by molecules such as arcRNAs and proteins containing intrinsically disordered, low-complexity domains. Multivalent interactions include charge, dipole-dipole, cation-π, π-π, and hydrophobic interactions. These interactions are very weak and short lived, enabling protein components of most bodies to be highly dynamic, rapidly exchanging with the surrounding nucleoplasm or cytoplasm. By contrast, arcRNA stays inside a nuclear body.