Exonic splicing enhancer

In molecular biology, an exonic splicing enhancer (ESE) is a DNA sequence motif consisting of 6 bases within an exon that directs, or enhances, accurate splicing of heterogeneous nuclear RNA (hnRNA) or pre-mRNA into messenger RNA (mRNA).

The central dogma of molecular biology states that all of the information that makes you unique is housed in the nucleus of every cell in your body in the form of DNA. The human DNA is a string of 3.2 billion base pairs. Short sequences of DNA are transcribed to RNA; then this RNA is translated to a protein. A gene located in the DNA will contain introns and exons. Part of the process of preparing the RNA includes splicing out the introns, sections of RNA that do not code for protein. The presence of exonic splicing enhancers is essential for proper identification of splice sites by the cellular machinery.

SR proteins bind to and promote exon splicing in regions with ESEs, while heterogeneous ribonucleoprotein particles (hnRNPs) bind to and block exon splicing in regions with exonic splicing silencers. Both types of proteins are involved in the assembly and proper functioning of spliceosomes.

During RNA splicing, U2 small nuclear RNA auxiliary factor 1 (U2AF35) and U2AF2 (U2AF65) interact with the branch site and the 3' splice site of the intron to form the lariat. It is thought that SR proteins that bind to ESEs promote exon splicing by increasing interactions with U2AF35 and U2AF65.

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