Phase Transition of a Disordered Nuage Protein Generates Environmentally Responsive Membraneless Organelles

• DOI: 10.1016/j.molcel.2015.01.013
• Publication Date: 2015-03-05T17:00:58Z
• Authors: Timothy J. Nott; Evangelia Petsalaki; Patrick Farber; Dylan Jervis; Eden Fussner; Anne Plochowietz; Timothy D. Craggs; David P. Bazett-J...; Tony Pawson; Julie D. Forman-Kay; Andrew J. Baldwin
• Keywords: 0301 basic medicine; Molecular Sequence Data; Static Electricity; Cytoplasmic Granules; Methylation; Time-Lapse Imaging; Article; Phase Transition; DEAD-box RNA Helicases; 03 medical and health sciences; Humans; Amino Acid Sequence; Molecular Biology; Cell Nucleus; Organelles; Microscopy, Confocal; Sequence Homology, Amino Acid; Osmolar Concentration; Cell Biology; DNA; Intracellular Membranes; Luminescent Proteins; Microscopy, Fluorescence; Mutation; HeLa Cells

Cells chemically isolate molecules in compartments to both facilitate and regulate their interactions. In addition to membrane-encapsulated compartments, cells can form proteinaceous and membraneless organelles, including nucleoli, Cajal and PML bodies, and stress granules. The principles that determine when and why these structures form have remained elusive. Here, we demonstrate that the disordered tails of Ddx4, a primary constituent of nuage or germ granules, form phase-separated organelles both in live cells and in vitro. These bodies are stabilized by patterned electrostatic interactions that are highly sensitive to temperature, ionic strength, arginine methylation, and splicing. Sequence determinants are used to identify proteins found in both membraneless organelles and cell adhesion. Moreover, the bodies provide an alternative solvent environment that can concentrate single-stranded DNA but largely exclude double-stranded DNA. We propose that phase separation of disordered proteins containing weakly interacting blocks is a general mechanism for forming regulated, membraneless organelles.