Effects of microRNAs on fucosyltransferase 8 (FUT8) expression in hepatocarcinoma cells.

Fucosyltransferase 8 (FUT8) catalyzes the transfer of α1,6-linked fucose to the first N-acetylglucosamine in N-linked glycans (core fucosylation). Increased core fucosylation has been reported during hepatocarcinogenesis, in both cell-associated and secreted proteins. Accordingly, increased core fucosylation of α-fetoprotein and α1-antitrypsin is currently used as a diagnostic and prognostic indicator. The present study provides new evidences that FUT8 can be regulated also through miRNA-mediated mechanisms. Using microRNA/target prediction programs, we identified miR-122 and miR-34a seed regions in the 3' untranslated region (3'UTR) of FUT8. Then we used human and rodents hepatocarcinoma cell lines to evaluate the impact of transfection of miR-122 and miR-34a mimics on FUT8 mRNA and protein levels. This study demonstrated that forced expression of these miRNAs is able to induce a decrease of FUT8 levels and also to affect core fucosylation of secreted proteins. The ability of miR-122 and miR-34a to specifically interact with and regulate the 3'UTR of FUT8 was demonstrated via a luciferase reporter assay. Since miR-122 and miR-34a downregulation is a common feature in spontaneous human hepatocarcinoma, our finding that these miRNAs are able to target FUT8 3'UTR suggests that, together with transcriptional and other post-transcriptional systems, a miRNA-mediated mechanism could also be involved in the increased core fucosylation observed in liver tumors. Moreover, these findings also point out that miRNAs may be widely involved in the regulation of glycosylation machinery.