AU-rich elements (AREs) are found in 3′ untranslated regions (3′ UTR) of many highly unstable mRNAs for mammalian early-response genes. The minimal AU sequence core within the ARE is the heptamer WAUUUAW, although from a functional point of view, several pentanucleotides clustered in close proximity are the key sequence motif that mediates mRNA degradation (1 ).