Influence of circular target RNA topology on miRNA stability and function

FEDERICO F WIGHTMAN; JERÓNIMO LUKIN; SEBASTIAN A GIUSTI; DAMIAN REFOJO; MANUEL DE LA MATA

Congreso; 26th Annual Meeting of the RNA Society; 2021

RNA Society

MicroRNAs are small regulatory RNAs which confer cells the possibility of fine-tuning gene expression at a post-transcriptional level. Consequently, regulation of miRNAs levels themselves is of crucial importance. Accordingly, the mechanisms of microRNA biogenesis and function have been studied extensively, while their degradation mechanism has acquired a lot of attention specially in the recent years.On the one hand, a mechanism called TDMD (for Target Directed MicroRNA Degradation) has emerged as the main process affecting miRNA turnover. During TDMD, targets with extensive base-pair complementarity towards the 3? end lead to miRNA degradation, contrary to the canonical target silencing. On the other hand, there have been reports proposing circular RNAs as microRNA sponges. However, although a plethora of publications claim to have expressed circRNAs as sponges that block miRNAs, their capability of cleanly over-expressing circRNAs without suffering from a linear ?leak? remains questionable. Thus, assigning the observed effects to the circRNAs while ignoring the counterpart linear transcripts might seem far-fetched.In this study, we aimed at shedding light on whether linear versus circular topologies of targets can produce different effects on both miRNA stability and function. We started by examining the well described CDR1as/miR-7/Cyrano network, where the lncRNA Cyrano destabilizes miR-7-5p through TDMD, while the circRNA CDR1as yields an apparent protection. By expressing a linear version of CDR1as in combination with knocking the endogenous circRNA, we show that the circular topology of CDR1as is crucial for its function. Furthermore, using a strategy in which we expressed an artificial circRNA aimed at binding miR-132, designed in way that it minimizes the linear leak, we showed that the differences between topologies are not circumscribed to CDR1as. Finally, we analyzed publicly available sequencing data to show that this kind of regulation is potentially widespread through a number of miRNAs and circRNAs during neuron differentiation.