TAL1 represses FBXW7 via miR-223 in TAL1-positive T-ALL. (A) Binding sites for miR-223 and the FBXW7 3′UTR are shown for three conserved and one poorly conserved site (bottom), as determined by the TargetScan algorithm. Position numbers refer to distance from the FBXW7 stop codon. (B) TAL1-negative miR-223 low T-ALL cell lines, SUP-T1 and DND-41, were retrovirally transduced to overexpress miR-223, and FBXW7 protein expression determined by immunoprecipitation/immunoblot. Loading controls are 10% of immunoprecipitation input. A representative blot from two independent experiments is shown. (C) FBXW7 protein expression was determined after transduction of TAL1-positive CCRF-CEM and Jurkat cells with miRZip-223 compared with a miRZip control. A representative blot from two independent experiments is shown. (D) TAL1 was depleted in TAL1-positive MOLT-16 and RPMI-8402 cells by lentiviral knockdown with two independent shRNAs, and FBXW7 protein expression was determined by immunoprecipitation/immunoblot. A representative blot from two independent experiments is shown.