|
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. AREs are defined as a region with frequent adenine and uridine bases in a mRNA. They usually target the mRNA for rapid degradation. 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.〔 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 Urich 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. HuD (also called ELAVL4) 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. ==ARE Element Classifications== *Class I ARE elements, like the c-fos gene, have dispersed AUUUA motifs within or near U-rich regions. *Class II elements, like the GM-CSF gene, have overlapping AUUUA motifs within or near U-rich regions. *Class III elements, like the c-jun gene, are a much less well-defined class—they have a U-rich region but no AUUUA repeats. No real ARE consensus sequence has been determined yet, and these categories are based neither on the same biological functions, nor on the homologous proteins.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「AU-rich element」の詳細全文を読む スポンサード リンク
|