FIG. 4.

Binding of the tropoelastin mRNA-binding protein relies more on RNA sequence than structure. (A) RNA oligomers 1 to 7 of various lengths were synthesized to cover overlapping regions of the 5′ 50-nt of rat tropoelastin exon 30. The oligomer lengths are as follows: 1, 21 nt; 2, 23 nt; 3, 40 nt; 4, 18 nt; 5, 13 nt; 6, 12 nt; and 7, 20 nt. A protected product was produced only with oligomer 4 (+), which is identical to the AluI RNA probe used in the experiments summarized in Fig. 3F. (B) Sequences of oligomer 4 and three mutant RNA oligomers (M1, M2, and M3), with the mutated bases underlined. (C) ³²P-labeled RNA oligomers were incubated with cytosolic extract from control adult lung fibroblasts (−) or cells treated with 50 pM TGF-β1 (+) for 48 h. A specific protected band was detected only with wild-type oligomer 4, and binding activity was decreased by treatment with TGF-β1.