Inhibition of transcription elongation did not alter 1A or 1B exon 2′/2 splicing patterns. (A) Analyses of exon 2′/2 expression in MELCs in the presence of 0, 50, 100, and 150 μmol/L of DRB. Cells were treated with DRB for 24 hours and RNAs analyzed for exon 2′ expression by the use of a common anti-sense primer located in exon 2 and sense primer located either at exon 1A or 1B. Ex2′ indicates Southern blot using exon 2′ as a probe; Ex2, Southern blot using exon 2 as a probe. (B) Analyses of exon 2′/2 expression in native promoter-driven 1A and 1B minigene stably transfected MELCs in the presence of 0, 50, 100, and 150 μmol/L of DRB. RNA collected from cells treated with DRB for 24 hours were analyzed for exon 2′ expression. Ex2′ indicates Southern blot using exon 2′ as a probe; Ex2, Southern blot using exon 2 as a probe. For each construct, 4 stable lines were performed per experiment. Each experiment was repeated at least 3 times.