The F2 3′flanking sequence limits mRNA expression. (A) Arrangement of the hybrid constructs. (B) Northern blot of cytoplasmic RNAs of cells cotransfected with the indicated hybrid constructs and the WT+300 E3 control. The bar diagram shows the fold difference relative to the F2 WT mRNA expression levels ± SD after normalization for transfection efficiency. Bars 1 to 5 represent the quantification of lanes 1 to 5.