Identification of MicroRNAs Involved in the Regulation of Human UGT1A, UGT2B7 and UGT2B15 Gene Expression

Abstract

BackgroundThe human UGT enzymes are responsible for the glucuronidation and elimination of a large number of clinically important drugs. Large interindividual variations of human hepatic drug glucuronidation have been observed in vitro, which cannot be entirely explained by the mechanisms studied so far. MicroRNAs (miRs) are small, non‐coding RNAs that regulate gene expression in a sequence‐specific manner. At present little is known about their role in the regulation of human UGTs. Here we sought to identify miRs that bind to the 3′UTR sequences of UGT1A (identical in all functional UGT1A isoforms), UGT2B7, and UGT2B15, representing the majority of UGTs involved in human drug glucuronidation.MethodsHEK293 cells were co‐transfected with a plasmid carrying the Firefly luciferase gene under the control of the respective UGT 3′UTR (wild‐type allele), a plasmid with Renilla luciferase (normalizer) and a miR. Using this approach we screened a commercial library containing all known human miRs.ResultsThe analysis identified multiple miRs (6 each for UGT1A and 2B7; 16 for 2B15) that down‐regulated reporter activity. Deletion of the predicted miR response element (MRE) abrogated this down‐regulation. Interestingly two miR‐21‐3p MREs in the UGT1A 3′UTR contained two different SNPs (one in each) that did not affect miR binding. Finally UGT1A and 2B15 shared common MREs for miR‐376b‐3p and miR‐103b.ConclusionsWe have identified 28 unique miRs that are likely involved in the regulation of expression of the majority of UGTs responsible for drug glucuronidation in humans. Further experiments will verify the effect of these miRs on UGT gene expression and enzyme activity in human cell lines and primary cultures.