Deletion of the 19-bp CT-motif from three silencer elements. The components of each plasmid are shown to the left of the expression data. (A) A series of plasmids utilizing the SV40 promoter, HS2 enhancer, and CR27 silencer are shown. The 19-bp CT-motif is shown in the pink box. (B) Transient transfection results showing the effect of deletions or replacement of the CT-motif in gamma-globin silencing vectors. Three copies of the 19-bp CT-motif are sequentially removed from region CR12 by a deletion analysis. The internal location of two motifs in CR21 (light orange boxes) was replaced simultaneously by a neutral sequence from a nonsilencing element (white box).
