FIG. 9.

Tra2 and Rbp1 bind the ISS independently but function synergistically. (A) Wild-type ISS RNA was incubated in the Drosophila S2 nuclear extract and UV cross-linked with increasing amounts of GST-Rbp1 and Tra2 protein. The concentration of Tra2 used (4 picomoles) is at the lower end of the range where repression is observed but has no effect on Rbp1 binding. (B) Limiting amounts of recombinant Rbp1 and Tra2 proteins were used in splicing assays to investigate the combined effect on the repression of M1 splicing. The substrate used in these assays is ftz-ISS. Symbols are as described for Fig. 1.