Effect of PNAs on the splicing of intron2. Splicing inhibition of intron2 in mdm2 pre-mRNA by seven PNAs (PNA2551, 2553, 2555, 2406, 2557, 2559 and 2561) targeted to the 3'-splice site of intron2. JAR cells were transfected with PNA (2 μM) for 24 h and subjected to RT-PCR analysis by using extracted total RNA. RT-PCR was performed with primer sets A and H (see Table 2), for the 5'-splice site of the intron2 (161 bp) and β-actin (223 bp) (as internal control), respectively. RT-PCR results with 27 PCR cycles for three PNAs (PNA2551, 2553 and 2555) (A) and four PNAs (PNA2406, 2557, 2559 and 2561) (B) are shown. The numbers under the figure indicate the relative amount (normalized to β-actin) of the target mdm2 splicing variant.