Lin28 may affect the translation of its associated mRNAs. (A) Mouse ES cells were transfected with Lin28 siRNA or control siRNA, and cell proteins isolated and subjected to Western blot analysis. (Top) Western blots using antibodies. (Bottom) Western blots of the same membranes but using an antibody specific for gapdh. Numbers in italics at the bottom indicate protein levels as percentage of Lin28 siRNA treated compared with control siRNA treated after normalization using gapdh signals. (B) Luciferase reporter constructs (Vasudevan and Steitz 2007) containing sequences from cdk4 3′ UTR (UTR), the middle (B1U2), or first (B1U1) part of cyclin B 3′ UTR, were transfected into HEK293 cells together with increasing amounts of Flag-Lin28. Luciferase activities were measured 24 h after the transfection and relative luciferase activities plotted. Luciferase activities from cells without Flag-Lin28 cotransfection were arbitrarily set as 100%. Results are representatives of at least three independent experiments. Numbers shown are means of duplicate samples. Shown on the right are schematic mappings of the individual fragments. Figures are not drawn to scale.
