Analysis of gamma-satellite DNA. (A) Promoter activity of gamma-satellite 8 DNA. The ∼1.9-kb gamma-satellite 8 DNA fragment was linked to a firefly luciferase reporter gene in a pGL2-basic, or beta-globin promoter vector, or beta-globin promoter plus locus control region (LCR) and was transfected into mouse MEL cells with the Renilla luciferase gene in phRL-CMV as an internal standard. The schematic structures of the vectors are shown in the left panel, and the luciferase activity is shown in the right panel. Values are means ± SD of three individual experiments in triplicate. (B) Enhancer blocking assay. Enhancer blocking assays were performed as previously described (Chung et al. 1993, 1997). The ∼1.9-kb human gamma 8 repeats were inserted into the SacI site between the mouse HS2 enhancer and human gamma-globin promoter-neomycin gene. Before transfection, each construct was linearized by AatII endonuclease. The average colony number obtained is relative to constructs without cHS4 between the enhancer and gamma-neomycin gene.