Exonic splicing enhancer
Encyclopedia
An exonic splicing enhancer (ESE) is a DNA sequence motif
Sequence motif
In genetics, a sequence motif is a nucleotide or amino-acid sequence pattern that is widespread and has, or is conjectured to have, a biological significance...

 consisting of 6 bases within an exon
Exon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...

 that directs, or enhances, accurate splicing
Splicing (genetics)
In molecular biology and genetics, splicing is a modification of an RNA after transcription, in which introns are removed and exons are joined. This is needed for the typical eukaryotic messenger RNA before it can be used to produce a correct protein through translation...

 of hetero-nuclear RNA (hnRNA) or pre-mRNA into messenger RNA (mRNA).

The Basics

The central dogma of molecular biology
Central dogma of molecular biology
The central dogma of molecular biology was first articulated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970:In other words, the process of producing proteins is irreversible: a protein cannot be used to create DNA....

 states that all of the information that makes you unique is housed in the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

 of every cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 in your body in the form of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

. The human DNA is a string of 3.2 billion base pairs. Short sequences of DNA are transcribed to RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

; then this RNA is translated to a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

. A gene located in the DNA will contain introns and exons. Part of the process of preparing the RNA includes splicing
Splicing (genetics)
In molecular biology and genetics, splicing is a modification of an RNA after transcription, in which introns are removed and exons are joined. This is needed for the typical eukaryotic messenger RNA before it can be used to produce a correct protein through translation...

 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.

Research

Computational methods were used to identify 238 candidate ESEs. ESEs are clinically significant because synonymous point mutations previously thought to be silent mutations located in an ESEs can lead to exon skipping and the production of a non functioning protein.

Disruption of an exon splicing ehancer in exon 3 of MLH1
MLH1
MutL homolog 1, colon cancer, nonpolyposis type 2 , also known as MLH1, is a human gene located on Chromosome 3. It is a gene commonly associated with hereditary nonpolyposis colorectal cancer.It can also be associated with Turcot syndrome....

 gene is the cause of HNPCC (hereditary non polyposis colorectal cancer) in a Quebec family.

There is evidence that these 236 hexamers that signal splicing are evolutionarily conserved.

External links

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