Wild-type A-Myb but not a DNA binding deletion mutant A-Myb transactivates the c-myc promoter in WEHI 231 cells.

(A) Exponentially growing WEHI 231 cells were electroporated, in duplicate, with 10 μg p1.6 Bgl in the absence (bar 1) or in the presence of 1, 5, 10, and 20 μg (bars 2-5, respectively) of the pLL1 A-myb vector, plus pECE parental vector DNA to have a final total DNA of 50 μg. Cell extracts were normalized for β-Gal expression and assayed for CAT activity. The data are presented as fold induction relative to the value of the p1.6 Bgl alone set at 1.0. Mean and SD were obtained from 2 independent experiments. (B) WEHI 231 cells were transiently transfected as described above, in the absence or in the presence of 2.5 μg of the empty pECE vector (bars 1-3) or 2.5 μg of the pLL1 A-myb construct (bars 4-7) with (bars 2, 3, 5, 6, and 7) or without (bars 1 and 4) increasing amounts of the pCAD1 vector: 5 μg (bars 2 and 5), 10 μg (bars 3 and 6), 20 μg (bar 7). CAT activity was determined as above and the data are representative of 2 experiments carried out in duplicate.