The disordered P granule protein LAF-1 drives phase separation into droplets with tunable viscosity and dynamics

P granules and other RNA/protein bodies are membrane-less organelles that may assemble by intracellular phase separation, similar to the condensation of water vapor into droplets. However, the molecular driving forces and the nature of the condensed phases remain poorly understood. Here, we show that the Caenorhabditis elegans protein LAF-1, a DDX3 RNA helicase found in P granules, phase separates into P granule-like droplets in vitro. We adapt a microrheology technique to precisely measure the viscoelasticity of micrometer-sized LAF-1 droplets, revealing purely viscous properties highly tunable by salt and RNA concentration. RNA decreases viscosity and increases molecular dynamics within the droplet. Single…

• AC
  American Cancer Society

  Award: RSG-12-066-01-DMC
• SS
  Searle Scholars Program

  Award: 12-SSP-217
• HF
  Human Frontier Science Program

  Award: RGP0007/2012
• DF
  Deutsche Forschungsgemeinschaft

  Award: EC369-3/1
• NO
  NIH Office of the Director

  Award: 1DP2 GM105453 A