FIG. 7.

Rbp1 binds the ISS independently of the CAAGR repeats. In the left panel, UV cross-linking assays carried out on ISS RNAs after incubation in S2 nuclear extracts both with (+) and without (−) added recombinant GST-Rbp1 fusion protein are shown. The labeled RNAs are the wild-type ISS, ISS RNAs with mutations in two repeats (2mt), three repeats (3mt), or all 5 repeats (5mt), and ISS RNA with the spacer region deleted (del28). The lane at the far left labeled “G” shows results from cross-linking with the GST protein without fused Rbp1 sequences. In the right panel, an identical cross-linking assay on labeled wild-type ISS RNA using increasing amounts (indicated by + and ++) of a six-His-Rbp1 fusion protein to supplement S2 nuclear extracts.