Let-7/miR-98 regulate Fas and Fas-mediated apoptosis.

Fas is ubiquitously expressed on a variety of cells and triggers apoptosis, which have critical roles in the immune system. MicroRNAs (miRNAs) have been recently identified as regulators that modulate target gene expression and are involved in diverse biological processes, such as cell proliferation and apoptosis. This study was undertaken to investigate the contribution of miRNA in the regulation of Fas expression and Fas-mediated apoptosis. Bioinformatics analysis indicated that Fas was a potential target of let-7/miR-98 family. Indeed ectopic expression of let-7/miR-98 reduced, whereas knockdown of endogenous let-7/miR-98 increased the expression of Fas at both mRNA and protein levels. Let-7/miR-98 was verified to target Fas 3' untranslated region directly by site-directed gene mutagenesis and reporter gene assay. More importantly, introduction of let-7/miR-98 could decrease the sensitivity to Fas-induced apoptosis. Furthermore, let-7/miR-98 expression was reduced in activation-induced cell death process, accompanied by increased expression of Fas. In conclusion, our study first demonstrated that let-7/miR-98 regulated Fas expression and the sensitivity of Fas-mediated apoptosis.