Cell-free Formation of RNA Granules: Low Complexity Sequence Domains Form Dynamic Fibers Within Hydrogels

Cell. 2012 May 11;149(4):753-67. doi: 10.1016/j.cell.2012.04.017.

Abstract

Eukaryotic cells contain assemblies of RNAs and proteins termed RNA granules. Many proteins within these bodies contain KH or RRM RNA-binding domains as well as low complexity (LC) sequences of unknown function. We discovered that exposure of cell or tissue lysates to a biotinylated isoxazole (b-isox) chemical precipitated hundreds of RNA-binding proteins with significant overlap to the constituents of RNA granules. The LC sequences within these proteins are both necessary and sufficient for b-isox-mediated aggregation, and these domains can undergo a concentration-dependent phase transition to a hydrogel-like state in the absence of the chemical. X-ray diffraction and EM studies revealed the hydrogels to be composed of uniformly polymerized amyloid-like fibers. Unlike pathogenic fibers, the LC sequence-based polymers described here are dynamic and accommodate heterotypic polymerization. These observations offer a framework for understanding the function of LC sequences as well as an organizing principle for cellular structures that are not membrane bound.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / cytology
  • Brain / metabolism
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / metabolism
  • Cell-Free System
  • Cytoplasmic Granules / chemistry
  • Cytoplasmic Granules / metabolism*
  • Embryonic Stem Cells / metabolism
  • Hydrogel, Polyethylene Glycol Dimethacrylate / metabolism*
  • Male
  • Mice
  • Models, Molecular
  • NIH 3T3 Cells
  • RNA / metabolism*
  • RNA-Binding Proteins / analysis*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / metabolism
  • Testis / cytology
  • Testis / metabolism
  • X-Ray Diffraction

Substances

  • RNA-Binding Proteins
  • Hydrogel, Polyethylene Glycol Dimethacrylate
  • RNA