Figure 3.

U1 anti-CAT constructs are equally active when directed to the terminal exon at a position either 5′ or 3′ of the poly(A) site. (A) Schematic map of the pOB₄CAT construct and targeted sites. (B) pOB₄CAT activity targeted by U1 anti-CAT constructs positioned 5′ or at two locations 3′ of the poly(A) site. NIH 3T3 cells were stably co-transfected with pOB₄CAT and U1 snRNA or U1 anti-CAT constructs and selected with 200–400 µg/ml neomycin as described in Materials and Methods. Measurement of CAT activity was carried out 4 weeks post-transfection. A representative of three experiments is presented.