Circular RNA Control of Vascular Smooth Muscle Cell Functions

C ircular RNAs (circRNA) are generated by an alternative RNA splicing process called backsplicing, in which a splice donor is spliced to an upstream acceptor thereby resulting in the formation of an RNA loop that is stably expressed.CircRNAs initially have been described in the 90s, but only recently computational analysis suggested that circRNAs are more prevalent than initially thought.Several studies have reported on regulatory activities in different biological processes, including the control of angiogenesis, smooth muscle cell functions, and cardiac injury responses. 1,2Evidence so far indicates that circRNAs predominantly act as noncoding RNAs but may also encode for peptides/proteins.Towards their mechanism of action, first studies suggested that they may act as microRNA (miRNA, miR) sponges preventing the biological activity of these small noncoding RNAs.However, circRNAs have also been shown to control transcription, bind to proteins and other RNAs thereby interfering with multiple effector pathways.