Psicheck2 vector

The 3′ UTR of the BAMBI sequence containing wild-type or mutant miR-20b-5p binding sites was inserted into the XhoI and NotI restriction sites of pmiR-RB-REPORT vector (Ribobio). The circDNMT3B sequence containing wild-type or mutant miR-20b-5p binding sites was inserted into the SgfI and NotI restriction sites of psiCHECK2 vector (Geneseed). The maps of pmiR-RB-REPORT and psiCHECK2 vectors were shown in Supplementary Fig. S1. Luciferase reporter vectors were co-transfected with miR-20b-5p mimic or miR mimic NC into 293T cells using Lipofectamine 3000 (Life Technologies). At 48 h after transfection, luciferase activities were detected with the Dual-Luciferase Reporter Assay System (Promega, Madison, WI, USA) using the Synergy H4 Multi-Mode Reader (BioTek, Winooski, VT, USA) according to the manufacturer's instructions. The binding of miRNA on RNA sequence leads to the depressed expression of Renilla luciferase (Rluc) and affects the luciferase activity.