FIGURE LEGENDS
Figure 1. Splicing motifs for exon recognition by the spliceosome. The acceptor (3’) and donor (5’) splice site motifs are shown. The U1 and U2 small nuclear ribonucleoprotein complexes recognize the donor splice site and the branchpoint (BP) site, respectively, while the U2AF proteins recognize the acceptor splice site and polypyrimidine tract located between the BP and 3’ splice site. Diverse sets of splicing regulatory elements refine exon recognition and regulate alternative splicing. Some exonic splicing enhancers (ESEs) bind Serine/Arginine-rich (SR) proteins and stabilize the binding of U2AF to promote splice site usage. Exonic splicing silencers (ESSs) bind heterogeneous nuclear ribonucleoproteins (hnRNPs) to inhibit splice site usage. Intronic splicing regulatory elements are not shown. Donor and acceptor splice site motif figures adapted from Cartegni, Chew, and Krainer (2002).