The Biological Functions of Non-coding RNAs: From a Line to a Circle.

Non-coding RNAs have gained increasing attention, as their physiological and pathological functions are being gradually uncovered. MicroRNAs are the most well-studied ncRNAs, which play essential roles in translational repression and mRNA degradation. In contrast, long non-coding RNAs are distinguished from other small/short non-coding RNAs by length and regulate chromatin remodeling, gene transcription and posttranscriptional modifications. Recently, circular RNAs have emerged as endogenous, abundant, conserved and stable in mammalian cells. It has been demonstrated that circular RNAs can function as miRNA sponges. Other possible biological functions of circular RNAs are still under investigation. In this review, the biogenesis and biological functions of the three major types of ncRNAs, including miRNAs, lncRNAs and circRNAs, are overviewed. In addition, the role of ncRNAs in human diseases and potential clinical applications of ncRNAs are discussed.