The mouse TrkB 5′ leaders are able to initiate translation when cap-dependent translation is inhibited.

<p>A) A dual monocistronic construct containing the pGL3 multiple cloning site upstream of the <i>Renilla</i> luciferase and the pGL3 multiple cloning site, EMCV, or the TrkB 5′ leaders upstream of the <i>Photinus</i> luciferase gene was co-transfected into C6 cells with a construct encoding for a hypophosphorylated 4EBP construct or a null vector. The level of <i>Photinus</i> luciferase activity from each mRNA, when co-transfected with the null vector, was normalized to 100 percent. The <i>Renilla</i> and <i>Photinus</i> luciferase activity obtained in cells co-transfected with hypophosphorylated 4EBP is represented as a percentage of the activity obtained in cells co-transfected with the null plasmid. B) Monocistronic <i>Photinus</i> luciferase mRNA containing the β-globin or TrkB 5′ leaders was <i>in vitro</i> translated in rabbit reticulocyte lysate in the presence of increasing concentrations of cap analog. <i>Photinus</i> luciferase activity for each mRNA in the absence of cap analog was set to 100 percent.