Nuclear RNA: a transcription-dependent regulator of chromatin structure.

Although the majority of RNAs are retained in the nucleus, their significance is often overlooked. However, it is now becoming clear that nuclear RNA forms a dynamic structure through interacting with various proteins that can influence the three-dimensional structure of chromatin. We review the emerging evidence for a nuclear RNA mesh or gel, highlighting the interplay between DNA, RNA and RNA-binding proteins (RBPs), and assessing the critical role of protein and RNA in governing chromatin architecture. We also discuss a proposed role for the formation and regulation of the nuclear gel in transcriptional control. We suggest that it may concentrate the transcriptional machinery either by direct binding or inducing RBPs to form microphase condensates, nanometre sized membraneless structures with distinct properties to the surrounding medium and an enrichment of particular macromolecules.