RT-PCR using primers T7/EBPR after cotransfection with the BX and SR plasmids. (a) Semiquantitative RT-PCR, using primers T7/EBPR, on cDNA from HeLa cells cotransfected with the BX plasmid together with a plasmid expressing one of the following proteins: SF2/ASF, SRp20, SRp40, SRp55, 9G8 and hnRNPA1. The BX lane is the control. The transcripts corresponding to each band are drawn on the right. (b) &(c) Quantification of radio-labelled RT-PCR for the different transcripts (b for transcripts including exon 3 versus transcripts lacking it, i.e. (1+2)/(3+4) and c for transcripts including exon 4 versus transcripts lacking it, i.e. (1+3)/(2+4)), considering BX transfection as 100% in each case. Each value is the mean ± S.E. of two independent experiments, each of which was replicated three times. * when p < 0.05.