ADAR1 controls the miR-381-3p-mediated expression of MRP4 by regulating the production of circHIPK3 in human renal cell

Multidrug resistance-associated protein 4 (MRP4), a member of the C subfamily of ATP-binding cassette transporters, is highly expressed in the kidney of mammals and responsible for renal elimination of various drugs. Adenosine deaminase acting on RNA 1 (ADAR1) has been reported to regulate gene expression through catalyzing adenosine-to-inosine (A-to-I) RNA editing. In this study, we found that the down-regulation of ADAR1 increased the expression of MRP4 in human renal cells at post-transcriptional level. The results of luciferase reporter assays and microarray analysis revealed that down-regulation of ADAR1 decreased the levels of miR-381-3p, which led to the up-regulation of MPR4 expression. Circular RNAs (circRNAs) are a kind of closed loop endogenous non-coding RNAs that play a critical role of gene expression by acting as miRNA sponges. ADAR1 repressed the biogenesis of circular RNA circHIPK3 by catalyzing A-to-I RNA editing, which changed the secondary structure of precursor of circHIPK3. In silico analysis suggested that circHIPK3 acted as a sponge of miR-381-3p. Indeed, overexpression of circHIPK3 up-regulated the expression of MRP4 through interfering with miR-381-3p. Our results provide the novel point of view for regulating mechanism of the expression of xenobiotic transporters through mediating the control of circRNA expression by RNA editing enzyme ADAR1. The down-regulation of ADAR1 induced microRNA expression in human renal proximal tubular epithelial cells were measured. The cells were infected with lentiviral particles expressing shRNA against the human ADAR1 gene (sc-37657-V; Santa Cruz Biotechnology) or empty lentiviral to construct mock-transduced RPTECs for the control.