Figure 1. Speculative models by which enhancer usage might influence alternative splicing choices through changes in RNAP II elongation rates. (A) Enhancer B interacts with the gene promoter and determines the recruitment of elongation factors that enhance RNAP II elongation rate through the body of the gene, thus promoting alternative exon skipping. (B) The intragenic enhancer A, located in the intron downstream of the alternative exon, interacts enhancer B. The resulting loop formation and protein complex recruitment to the region induces RNAP II stalling upregulating alternative exon inclusion.