miR-28 recognizes the MPL 3′UTR and inhibits its translation. (A) γ2A cells were cotransfected either with 0.8 μg MPL 3′UTR luciferase reporter (gray histograms) or MPL 3′UTR luciferase reporter mutated for the site of interest (black histograms) and either 40nM Pre-miR-28, Pre-let-7a, 7c, 7d, 7e, 7f, Pre-miR-98 or Pre-miR-control. Values represent the mean luciferase activity ± SD of 3 independent experiments relative to Pre-miR-control transfected cells. The 1680 nt MPL 3′UTR sequence was cloned after the stop codon of the luciferase and is represented with the mRNA coordinates of the putative miR binding sites (gray boxes). (B) Mo7e cells were transduced with a bicistronic retroviral vector expressing miR-28 together with the green fluorescent protein (GFP). After sorting for equivalent GFP levels, cell lines expressing either the empty vector (pMegix) or the miR-28 expressing vector (miR-28) were subjected to Western blotting for MPL protein levels. The histogram reports MPL relative bands intensities measured on Western blot.