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).