FIG. 7.

A proposed model for U2AF⁵⁹-insensitive splicing. (A) The U1 snRNP interacts with the 5′ SS and U2AF interacts with the Py-tract/3′ SS. The SF1/BBP, SAP155, and U2 snRNPs interact with the BPS. RNA-RNA and RNA-protein interactions are shown by downward arrows. Horizontal two-sided arrows represent interactions between splicing factors. The question mark in panel B represents residual activity of the U2AF large subunit or another factor that may functionally substitute for it. The dashed line in panel C represents suboptimal features or mutations/alterations in the 5′ SS, the G7 position, spacing between the 5′ SS and the BPS, or portions of nucleotides 1 to 30 of bpb1_a that render this intron U2AF⁵⁹ sensitive. Exons are represented as boxes, and introns are shown as lines.