FIGURE 2.

Effect of intron inclusion on the level of expression of a range of human genes. Western analysis of the level of protein expression for each of 10 different genes in 293T cells transfected with 400 ng each of a matched intron⁺ or intron⁻ expression plasmid, together with pCMV/β-gal as an internal control. The relative increase in the level of expression of each protein that is seen upon intron inclusion is indicated at the bottom after normalization to the internal control. An average of three independent experiments with standard deviation is indicated. (The intronless β-globin construct gave rise to a level of protein expression that was 2.8 ± 1.8% of the level seen when an intron was present in cis.)