Figure 1
From: Use of viral promoters in mammalian cell-based bioassays: How reliable?
Expression of CAT activity by transfected reporter vectors PRE-tk-CAT, MMTV-CAT and UG-CAT into T47 D and MCF-7 cells without the induction by progesterone (in triplicate from six experiments,). MCF-7 cells show over all higher basal expression of CAT activity. Activity of pUG-CAT was 5 fold and that of pPRE-tk-CAT was 2.5 fold in the MCF 7 than in theT47 D cell line. pMMTV-CAT expressed no basal CAT activity in T47 D and minimal basal CAT activity in MCF-7 cell line. The variations in the basal expression viral promoters, in an akin cell milieu of cofactors and number of PR sites suggest that the ligand-independent expression is a "promoter context" occurrence and may have bearing on the ligand induced transcription response profile.