(A) Reduction in β-Gal activity from three separate transient U1 anti-β-Gal–RSV β-Gal cotransfection experiments. (B) Titration of various amounts of pOB4CAT to 10 μg of U1 anti-CAT568, yielding approximate molar ratio of CAT to U1 anti-CAT of 4:1, 2:1, 2:3, and 1:5 respectively. (C) Reduction of CAT enzyme activity by U1 anti-CAT448 and anti-CAT568 using cotransfection. (D) Sequence-specific reduction of CAT activity in transient U1 anti-CAT-pOB4CAT cotransfection experiments. pOB4CAT was used in lanes 1 and 2, and pOB4CAT 737PvuII was used in lanes 3 and 4. The U1 snRNA constructs were as follows: lane 1, U1 snRNA; lane 2, U1 anti-CAT737; lane 3, U1 anti-CAT737; lane 4, U1 anti-CAT737PvuII. These constructs were transiently cotransfected with TK-luciferase construct into NIH 3T3 cells. Error bars, standard deviations.