Adenylate-uridylate-rich elements (AU-rich elements; AREs) are found in the 3' untranslated region (UTR) of many messenger RNAs (mRNAs) that code for proto-oncogenes, nuclear transcription factors, and cytokines. AREs are one of the most common determinants of RNA stability in mammalian cells.[1] The function of AREs was originally discovered by Shaw and Kamen in 1986.[2]
AREs are defined as a region with frequent adenine and uridine bases in a mRNA. They usually target the mRNA for rapid degradation.[3][2]
ARE-directed mRNA degradation is influenced by many exogenous factors, including phorbol esters, calcium ionophores, cytokines, and transcription inhibitors. These observations suggest that AREs play a critical role in the regulation of gene transcription during cell growth and differentiation, and the immune response.[1] As evidence of its critical role, deletion of the AREs from the 3'UTR in either the TNF gene or GM-CSF gene in mice leads to over expression of each respective gene product, causing dramatic disease phenotypes.[4][5]
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. HuA, HuB, HuC, HuD, HuR) bind to these elements and stabilise the mRNA while others (AUF1, TTP, BRF1, TIA-1, TIAR, and KSRP) destabilise the mRNA, miRNAs may also bind to some of them.[6] For example, the human microRNA, miR16, contains an UAAAUAUU sequence that is complementary to the ARE sequence and appears to be required for ARE-mRNA turnover.[7]HuD (also called ELAVL4) binds to AREs and increases the half-life of ARE-bearing mRNAs in neurons during brain development and plasticity.[8]
AREsite—a database for ARE containing genes—has recently been developed with the aim to provide detailed bioinformatic characterization of AU-rich elements.[9]
^ abChen, Chyi-Ying A.; Shyu, Ann-Bin (November 1995). "AU-rich elements: characterization and importance in mRNA degradation". Trends in Biochemical Sciences. 20 (11): 465–470. doi:10.1016/S0968-0004(00)89102-1. PMID8578590.
^ abShaw G, Kamen R (August 1986). "A conserved AU sequence from the 3' untranslated region of GM-CSF mRNA mediates selective mRNA degradation". Cell. 46 (5): 659–667. doi:10.1016/0092-8674(86)90341-7. PMID3488815. S2CID40332253.