ESE

Exonic splicing enhancers:

Exonal sequences have a prominent role in promoting exon definition and inclusion in mature transcripts (mRNA). The best understood exonic elements include the so-called exonic splicing enhancers (ESEs). ESEs provide binding sites for SR proteins, which are thought to have a role in the initial steps of spliceosome assembly (3–5).

Sequences that act as exonic splicing silencers (ESSs) have also been described (6–11) but are less well characterized than ESEs. In some instances, ESSs have been shown to bind negative regulators belonging to the heterogeneous nuclear ribonucleoprotein (hnRNP) family (11,12).

The function of ESEs and ESSs appears to be especially important for the regulation of alternative splicing events, but these sequences probably also play a relevant role in the definition of constitutive exons.

Bipartite exonic splicing regulatory elements are known in HIV-1, papillomavirus, and the human fibronectin gene. Papillomavirus has bipartite splicing regulatory element that consists of a purine-rich positive element known as an exonic splicing enhancer (ESE) and a pyrimidine-rich negative element known as an exonic splicing suppressor (ESS). [s]