Interaction hot spots for phase separation revealed by NMR studies of a CAPRIN1 condensed phase

Significance Many important biological processes occur within biomolecular condensates. Unlike many organelles, these condensates lack a surrounding membrane but are formed by phase separation due to interactions of their molecular components. Although the important role of intrinsically disordered protein regions (IDRs) in condensates is appreciated and contributing amino acids have been identified, experimentally derived site-specific information reporting on interactions between IDRs in condensed phases is lacking. Using a suite of NMR experiments with improved resolution and sensitivity for studies of condensed phases, we have obtained quantitative and site-specific information on interactions and hot spots that govern phase separation of the C-terminal IDR of CAPRIN1 and how phase separation can be modulated by posttranslational modifications, mutations, and interactions with ATP.