Figure 3.

Low luciferase activity of cells containing pHS2(7.3λ)γluc is unrelated to template copy number. (A) The pHS2(2.2λ)γluc and pHS2(7.3λ)γluc constructs were linearized and cotransfected into K562 cells. Stably transfected clonal cell lines were isolated and assayed for luciferase activity as a measure of γ-globin promoter activity. (Inset) Mean luciferase activity of each set of clones [mean ± SEM, n = 15 and 8 for pHS2(2.2λ)γluc and pHS2(7.3λ)γluc constructs, respectively]. (B) Southern blot analysis of integrated templates. Genomic DNA was purified from the clonal cell lines of A and digested to completion with HindIII and XbaI to excise a fragment containing the γ-globin promoter linked to the luciferase gene. Genomic DNA (15 μg) was analyzed by Southern blot analysis with a luciferase probe.