FIG. 9.

PRE function in murine cells overexpressing PTB. (A) Western blot of DBT cells stably transfected with a plasmid expressing human PTB (lane 2) or empty vector plasmid (lane 1). The former cells express approximately twice as much of the long form of PTB as the latter cells. The short form is not expressed from the cDNA expression plasmid, since it is generated by alternative splicing. Numbers at right are kilodaltons. (B) Cells were transfected with pDM138, pDM138-PRE, or mutant 34. After 2 days, the cells were harvested and assayed for CAT activity. The data are the mean and standard deviation for three transfections and represent the relative amount of CAT activity in cells transfected with either pDM138-PRE or mutant 34, normalized to the amount of CAT activity in cells transfected with pDM138.