Fig. 2.

A schematic representation of AS regulated by cis-acting elements and trans-acting factors. The cis-acting elements ESEs and ESSs represent exonic splicing enhancers and silencers, respectively. ISEs and ISSs represent intronic splicing enhancers and silencers, respectively. SR proteins, hnRNPs, or other trans-acting factors bind to cis-acting elements for positive or negative AS regulation by affecting the recruitment or recognition of spliceosome components to splice sites; for example, U1 binds to the 5′ splice site, while U2AF and U2 bind to the 3′ splice site