FIGURE 4.

Effect of introns on β-globin gene expression. (A) Western analysis of β-globin expression levels. 293T cells were either mock transfected or transfected with 400 ng of pCMV/WT/GLB, pCMV/δ1/GLB, pCMV/δ2/GLB, or pCMV/δ1+2/GLB together with 200 ng pCMV/β-gal as an internal control. (B) This RPA was performed as described in Figure 1C ▶. (C) This quantitation was performed as described in Figure 1D ▶. (D) The level of nuclear 3′ end-processed β-globin RNA in 293T cells transfected with the indicated expression plasmids is given as a percentage of total nuclear β-globin RNA, as determined by RPA.