Organization and function of paraspeckles

Paraspeckles are a type of subnuclear bodies built on the long noncoding RNA NEAT1 (nuclear paraspeckle assembly transcript 1, also known as MEN-ε/β or VINC-1). Paraspeckles are involved in many physiological processes including cellular stress responses, cell differentiation, corpus luteum formation and cancer progression. Recently, ultra-resolution microscopy coupled with multicolor-labeling of paraspeckle components (the NEAT1 RNA and paraspeckle proteins) revealed the exquisite details of paraspeckle structure and function. NEAT1 transcripts are radially arranged to form a core–shell spheroidal structure, while paraspeckle proteins (PSPs) localize within different layers. Functional dissection of NEAT1 shows that the subdomains of NEAT1_2 are important for RNA stability, isoform switching and paraspeckle assembly via a liquid–liquid phase separation (LLPS) mechanism. We review recent progress on structure and organization of paraspeckles as well as how paraspeckles spatiotemporally control gene regulation through sequestration of diverse proteins and RNAs in cells.