FIGURE 1.

Homologous rat sequences can partially substitute for the intronic enhancer but not the silencer in intron 10 of human gene. Schematic diagram of human IR minigene chimeras with rat sequence substitutions is shown on left. White boxes represent human exons 10 and 11 separated by intron 10. Dotted lines indicate deletions in the intervening intron. Gray boxes indicate the homologous sequence from the rat Insr gene. Numbers below the introns indicate sizes of deletions. Numbers above the intron and gray boxes indicate length of human or rat sequence. The positions of the human intronic splicing enhancer (ISE) or silencer (ISS) are indicated in hIRB. These minigenes were transfected into HepG2 cells. Total RNA was isolated 48 h post-transfection and was subjected to RT-PCR analysis using primers specific to the transfected IR minigene mRNA. The mean ± S.E. for percent exon 11 inclusion is shown as a bar graph on the right. Results are derived from at least three independent experiments. Statistical significance was analyzed by ANOVA. Bars with the same letter are not significantly different (p < 0.05).