Preventing the spread of repression

Scientists at the Friedrich Miescher Institute for Biomedical Research have identified a novel and unexpected regulatory activity of RNA at the edge of inactive chromosomal regions. In their publication they showed that non-protein coding RNAs demarcate active and inactive chromosomal regions by evicting the proteins necessary for the spreading of repressive chromatin marks. It was one of the bigger surprises of the human genome project: Even though the human genome is about 30 times bigger than the one of the roundworm C. elegans , it contains only one third more protein-coding genes than that of the simple worm. This was a shock to those who up until then quantified the complexity of an organism through the numbers of genes, and scientists had to turn their attention to the 98% of the human genome that does not code for proteins. Since then it has become evident that vast DNA regions not only regulate gene expression and organize the architecture of the chromosomes but also contain the templates for non-coding RNAs such as tRNA, rRNA or microRNA. While the function of some of these RNAs, for example in protein synthesis and RNA processing, has been known for a while, the functional relevance for most of the other non-coding RNAs that have been catalogued remain elusive. Marc Bühler and his team at the Friedrich Miescher Institute for Biomedical Research have now discovered a so far unknown activity of non-coding RNAs.