Addressing the challenge of in situ structural studies of RNP granules in light of emerging opportunities

Abstract

The emerging concept of phase separation in cell biology postulates that, in concert with the classical structural view of stoichiometric quaternary complexes, ribonucleoproteins (RNPs) and nucleic acids are intricately involved in the formation of meso-scale membraneless compartments, commonly termed RNP granules. Elucidating the structural basis underlying such non-deterministic assemblies remains challenging due to their inherent compositional heterogeneity, conformational flexibility and biophysical dynamics. Techniques which allow characterization of their molecular architectures, ideally within the native cellular environment, are therefore required. We review advances in in situ methods that can provide data on the molecular organization in RNP granules from the level of amino-acid interactions, up to their complex cross-talk in cells. These data combined into integrative modeling and multi-scale simulation frameworks will provide an understanding of RNP granules on a continuum scale of spatial resolutions to elucidate their structure-dynamics-function relations.