FIG. 4.

Transcription of the luciferase reporter gene in individual stable transfectants is slightly stimulated by the MAR in the 5′ LCR and strongly by the E6 MAR and does not significantly depend on the site of chromosomal integration. Four individually isolated stable transfectants of EP-Luc into HeLa cells showed nearly undetectable levels of luciferase expression, which is significantly stimulated by the presence of the MAR in the 5′ LCR (L-EP-Luc) in four individual clones. Fusion of these constructs with the E6 MAR leads to a further 10- to 20-fold stimulation of luciferase expression in eight independent stable transfectants (L-EP-Luc-E6).