The Pros and Cons of Circular RNAs as miRNA Sponges

The roles that noncoding RNAs play in various cells have been a focus of intense research in recent years. Circular RNAs (circRNAs) are noncoding RNAs that were initially thought to be junk by-products of splicing. Many circRNAs have been found to demonstrate important regulatory functions and, in particular, to act as miRNA sponges. The function of an miRNA sponge was compared with the function of a classic transcription factor (TF)-dependent regulatory loop in terms of efficiency, working rate, and noise characteristics. A circRNA with multiple binding sites for miRNA was found to act more efficiently than a TF and the respective loop worked faster, but only when the binding sites were not fully saturated with miRNA molecules. The noise characteristics of the circRNA loop were significantly worse with an increasing number of binding sites. A circRNA with one binding site was shown to be inefficient as an miRNA sponge. The circRNA-mediated regulation was assumed to provide a specific tool to the cell. © 2021, Pleiades Publishing, Inc.