FIG. 2.

U2AF⁶⁵ UV cross-linking next to SAP 155 in the A complex. (A) Nucleotide sequence of the 3′ portion of the AdML intron. The arrow indicates the G residue that was site-specifically labeled. The SAP 155 cross-linking sites in the A complex are indicated. At the +13 site, the UU was changed to GC in order to transcribe the 3′ RNA for site-specific labeling (see Materials and Methods). This alteration has no effect on A complex assembly or splicing. (B) The proteins that cross-link at the +13 site in the H, E, and A complexes are shown next to IVT U2AF⁶⁵ (as a marker). (C) Pre-mRNA site-specifically labeled at +13 was assembled into the E complex and UV cross-linked, and then an immunoprecipitation (IP) with U2AF⁶⁵ antibodies was carried out. IVT U2AF⁶⁵ was run as a marker.