The New RNA World: Growing Evidence for Long Noncoding RNA Functionality

The past decade has seen a major increase in the study of noncoding RNAs (ncRNAs). However, there remains a great deal of confusion and debate over the levels of functionality and mechanisms of action of the majority of these new transcripts. This Opinion article addresses several of these issues, focusing particularly on long ncRNAs (lncRNAs). We reemphasize the unique abilities of RNAs to form myriad structures as well as to interact with other RNAs, DNA, and proteins, which provide them with unique and powerful abilities. One of these, the ability to interact sequence specifically with DNA, has been largely overlooked. Accumulating evidence suggests that evolution has taken advantage of RNA's properties via the rapid acquisition of new noncoding genes in testes, with subsequent gains of function in other tissues. This amplification process appears to be one of the major forces driving metazoan evolution and diversity.