Long Non-coding RNAs and Nuclear Body Formation and Function

A significant challenge facing biologists of our era is determining a function for the thousands of long noncoding RNAs transcribed from the genomes of complex organisms. One area that has been highly influential in this regard is nuclear organization, as it has emerged that one of the best-studied roles of long noncoding RNAs (lncRNAs) is to form subnuclear structures and/or influence their function. Essentially, there are two types of lncRNA in nuclear organization: lncRNAs that form subnuclear bodies as essential structural scaffolds (for example, NEAT1 in paraspeckles, Satellite III (SatIII) lncRNA transcripts in nuclear stress bodies (nSBs), hsr-ω-n in omega speckles in Drosophila, and MIAT in gomafu speckles), and lncRNAs that are localized to subnuclear bodies, but are not known to be crucial for their formation (for example, MALAT1 in nuclear speckles and TUG1 in polycomb bodies). Studies on these nuclear lncRNAs have led to a wealth of insights into the way lncRNAs nucleate subnuclear bodies, their interacting protein partners and their spatial organization. Importantly, functions have also been elucidated, with a common theme emerging that lncRNA associated subnuclear bodies influence gene expression at both the transcriptional and posttranscriptional levels. Our current knowledge may well represent just the tip of the iceberg in terms of the actual numbers of lncRNAs involved in nuclear organization, and the types of functions they may have in controlling gene expression.