FIG. 7.

Exon 30 confers regulated mRNA turnover and responsiveness to TGF-β1. (A) Human PE cells were transfected a full-length (exons 1 to 36) or a truncated (exons 1 to 29) bovine tropoelastin cDNA under the control of a CMV promoter. Stable cell lines were selected and pooled. For the experiment shown, some cells of each group were treated with 50 pM TGF-β1 and, 24 h later, some control and treated cells were harvested (0 h). The remaining cells were treated with 10 μg of actinomycin D per ml with or without TGF-β1 and were harvested 16 and 24 h later. Tropoelastin and GAPDH mRNAs were assayed by RT-PCR and Southern hybridization. (B) PE cells were transfected with full-length (1-36) bovine tropoelastin cDNA or with a deletion mutant lacking exon 30 (Δ30), and stable cell lines were selected and pooled. Cells of each group were treated with 50 pM TGF-β1 and, 24 h later, RNA was isolated. Tropoelastin mRNA was assessed by Northern hybridization. Loading equivalence among lanes was demonstrated by ethidium bromide staining (not shown).