Soft active aggregates: Mechanics, dynamics and self-assembly of liquid-like intracellular protein bodies

Intracellular bodies consisting of dynamic aggregates of concentrated proteins and often RNA are a ubiquitous feature of the cytoplasm and nucleus of living cells. Dozens of different types of protein bodies are involved in diverse physiological processes including ribosome biogenesis, RNA splicing, and cell division. Unlike conventional organelles, they are not defined by an enclosing membrane. Instead, these bodies represent dynamic patterns of locally concentrated macromolecules which turn over on timescales of seconds. Here we discuss recent findings suggesting that intracellular protein bodies are active liquid-like drops that self-assemble within an intrinsically structured cytoplasm.