FIG. 5.

The repeat multimer is not sufficient to support Tra2 repression and binds Tra2 weakly. (A) Parallel splicing assays are shown for the ftz control substrate (ftz), a similar substrate with the ISS inserted (ftz-ISS), and a substrate in which a multimer containing 5 copies of the sequence CAAGA was substituted for the ISS in ftz-ISS (multimer). Splicing percentages and maximal relative (n-fold) repression are shown below the gel. (B) Cross-linking of Tra2 to the same CAAGA RNA multimer is compared to that with the ISS (ISS) and ISS sequences with mutated repeats (5mt). Reactions were carried out in Drosophila S2 nuclear extracts both in the presence (+) and absence (−) of recombinant Tra2 protein. The position of cross-linked recombinant Tra2 is indicated. The cross-linked RNAs did not include splice junction or branch point sequences. Mutant repeats and symbols are like those described for Fig. 3.