The F2 3′end formation signal is less efficient than the HBB signal. (A) Arrangement of the tandem constructs. (B) Northern blot of cytoplasmic RNA of cells cotransfected with the indicated tandem constructs and the WT+300 E3 control. The 3′FS of the HBB gene of the 5′ site is shorter than the 3′FS of the F2 gene. The HBB-HBB/HBB RNA (lane 2) processed at the 5′ site thus migrates faster than the respective F2-F2/F2 and F2-F2/HBB RNAs. The quantification of the signals (lanes 1-3) after normalization for the transfection efficiency control is shown in the bar diagram. The y-axis shows mRNA expression relative to F2-F2/F2, lane 1.