From bacteria to humans, chromatin to elongation, and activation to repression: The expanding roles of noncoding RNAs in regulating transcription.

Noncoding RNAs (ncRNAs) have emerged as key regulators of transcription, often functioning as trans-acting factors akin to prototypical protein transcriptional regulators. Inside cells, ncRNAs are now known to control transcription of single genes as well as entire transcriptional programs in response to developmental and environmental cues. In doing so, they target nearly all levels of the transcription process from regulating chromatin structure through controlling transcript elongation. Moreover, trans-acting ncRNA transcriptional regulators have been found in organisms as diverse as bacteria and humans. With the recent discovery that much of the DNA in genomes is transcribed into ncRNAs with yet unknown function, it is likely that future studies will reveal many more ncRNA regulators of transcription.