FIG. 5.

Directionality of hnRNP A1 cooperative spreading. (A) Sequences of synthetic RNA transcripts for UV cross-linking experiments. The radiolabeled cytidines are indicated in bold italic. The underlined hexanucleotide is a high-affinity hnRNP A1 binding site (ESS). The top transcript (5′ to 3′ binding) has radiolabeled cytidines downstream of the ESS, whereas in the bottom transcript (3′ to 5′ binding), they are upstream of the ESS. (B) UV cross-linking with 16 nM WT transcript (5′ to 3′ binding) or its ESSm (MUT) version in the presence of increasing recombinant hnRNP A1 (0.05 to 0.4 μM). Detection and quantitation of the cross-linked products were as for Fig. 1B. (C) As for panel B but with 3′ to 5′ binding WT and MUT transcripts.