AU-rich element

AU-rich elements are one of the most common types of regulatory elements found in mRNAs. They are involved in the control of gene expression. They are the most common determinant of RNA stability in mammalian cells.

An AU-rich element or "ARE" is defined as a region with frequent adenine and uridine bases in a mRNA. They usually target the mRNA for degradation. It is estimated that 5-8% of human mRNAs contain ARE's, particularly cytokine, proto-oncogenes and transcription factor mRNAs.

AREs are usually located in the 3' UTR. AREs have been divided into three classes with different sequences. The best characterised Adenylate Uridylate (AU)-rich Elements have a core sequence of AUUUA within U rich sequences (for example WWWU(AUUUA)UUUW where W is A or U). This lies within a 50-150 base sequence, repeats of the core AUUUA element are often required for function.

A number of different proteins (e.g HuR, AUF) bind to these elements and destabilise or stabilise the mRNA, miRNAs may also bind to some of them. HuD (also calledELAVL4) binds to AREs and increases the half-life of ARE-bearing mRNAs in neurons during brain development and plasticity.

AREsite - a database for ARE containing genes - has recently been developed with the aim to provide detailed bioinformatic characterization of AU-rich elements.