The long and the short of RNA maps

The landscapes of mammalian genomes are characterized by complex patterns of intersecting and overlapping sense and antisense transcription, giving rise to large numbers of coding and non-protein-coding RNAs (ncRNAs). A recent report by Kapranov and colleagues(1) describes three potentially novel classes of RNAs located at the very edges of protein-coding genes. The presence of RNAs from one of these classes appears to be correlated with the expression levels of their associated genes. These results suggest that a proportion of these RNAs might have roles in the cis-regulation of neighbouring protein-coding genes' expression.