FBXO31 regulates miR-93 and miR106a via degradation of Slug. (A) Slug enhances the expression of miR-93 and miR-106a at the transcriptional level. MCF7 cells were transfected with either empty vector or Slug, and transcriptional level of miR-93 and 106a was measured by real-time RT-PCR. (B) MicroRNAs levels were ablated upon overexpression of FBXO31. MCF7 cells were transfected with empty vector/FBXO31 for 48 hours. Total RNA was used to prepare cDNA, and levels of miR-93 and 106a were measured by real-time RT-PCR. (C) Depletion of FBXO31 enhanced the miR-93 and miR-106a levels. (D) The location of E-box consensus binding sites (5′-CAGGTG-3′ or 5′-CACCTG-3′) in the promoter of human miR-93 (upper panel). ChIP assay for recruitment of Slug at the promoter of miR-93 (lower panel). (E) MiR-93 and miR-106a inhibit FBXO31-mediated senescence. Transfected cells were irradiated with IR and were allowed to proliferate for 10 days. Then, cells were stained for β-galactosidase assay. Approximately 500 cells were counted for each case. The data are presented as mean ± SD, *P = .001, **P < .001.