FIGURE 2.

Membrane-less compartments in the cell and their involvement in aggregation with aging (A) Liquid-liquid phase separation requires often, but not always, the presence of RNA and RNA-binding proteins. RNA-binding proteins contain RNA-recognition motives and a low-complexity domain in their protein sequences. (B) Due to the high concentration of proteins in liquid droplets, a strict protein homeostasis is required to prevent phase transitions from liquid-like compartments to less dynamic states. Although transition from hydrogel to liquid droplet is in some cases still possible, liquid-to-solid and gel-to-solid transitions normally result in the formation of pathological fibrils and insoluble aggregates.