Paraspeckles: Where Long Noncoding RNA Meets Phase Separation.

Long noncoding RNA (lncRNA) molecules are some of the newest and least understood players in gene regulation. Hence, we need good model systems with well-defined RNA and protein components. One such system is paraspeckles - protein-rich nuclear organelles built around a specific lncRNA scaffold. New discoveries show how paraspeckles are formed through multiple RNA-protein and protein-protein interactions, some of which involve extensive polymerization, and others with multivalent interactions driving phase separation. Once formed, paraspeckles influence gene regulation through sequestration of component proteins and RNAs, with subsequent depletion in other compartments. Here we focus on the dual aspects of paraspeckle structure and function, revealing an emerging role for these dynamic bodies in a multitude of cellular settings.