Non-coding RNAs: Lost in translation?

In the last ten years, several RNAs with no protein-coding potential have been accumulating in RNA databases and are in need of further molecular characterization. At the same time, examples of non-coding RNAs (ncRNAs) such as microRNAs, small RNAs, small interfering RNAs (siRNAs) and medium/large RNAs with various functions have been described in the literature. Recent evidence points to a widespread role of these molecules in eukaryotic cells, suggesting that the majority of the new ncRNA examples might have specific functions. The aim of this review is to describe several new functional ncRNAs that have been recently identified and characterized, providing some clues that these molecules might not be produced by chance or as by-products of transcription as has been speculated.