FIG. 5.
Differential regulation of the synthesis of the 51- and 48-kDa FLI-1 isoforms by the conserved region −49/−33. Capped and uncapped Fli-1 mRNAs harboring progressive deletions of the 5′UTR were synthesized by in vitro transcription. Equal amounts of each of these synthetic Fli-1 mRNA were used to program rabbit reticulocyte lysates in the presence of [35S]methionine. Translation products were separated by SDS-PAGE. Labeled translation products were then visualized by autoradiography, and radioactive signals corresponding to the 51- and 48-kDa proteins were quantified using a Molecular Imager. (A) Schematic representation of synthetic Fli-1 mRNA. The open boxes represent the −49/−33 conserved region in 5′UTR, and the solid boxes represent coding sequences. (B) Graphical representation of the results of the quantitation of the 51-kDa (top) or 48-kDa (bottom) isoforms synthesized with the capped (C) or uncapped (UC) versions of each Fli-1 mRNA. The y axis shows arbitrary units of radioactivity, and the x axis shows the type of mRNA used for translation. (C) Autoradiography of the gel.