Nuclear bodies: The emerging biophysics of nucleoplasmic phases

The cell nucleus contains a large number of membrane-less bodies that play important roles in the spatiotemporal regulation of gene expression. Recent work suggests that low complexity/disordered protein motifs and repetitive binding domains drive assembly of droplets of nuclear RNA/protein by promoting nucleoplasmic phase separation. Nucleation and maturation of these structures is regulated by, and may in turn affect, factors including post-translational modifications, protein concentration, transcriptional activity, and chromatin state. Here we present a concise review of these exciting recent advances, and discuss current and future challenges in understanding the assembly, regulation, and function of nuclear RNA/protein bodies.