A 20-nucleotide (A + U)-rich element of beta2-adrenergic receptor (beta2AR) mRNA mediates binding to beta2AR-binding protein and is obligate for agonist-induced destabilization of receptor mRNA.

The Mr 35,000 beta-adrenergic receptor mRNA-binding protein, termed betaARB protein, is induced by beta-adrenergic agonists and binds to beta2-receptor mRNAs that display agonist-induced destabilization. A cognate sequence in the mRNA was identified previously that provides for betaARB protein binding in vitro. In the present work, the sequence established in vitro for binding of betaARB protein to hamster beta2-adrenergic receptor mRNA was probed in vivo by site-directed mutagenesis of the 3'-untranslated region and expression in Chinese hamster ovary cells. A 20-nucleotide, (A + U)-rich region in the 3'-untranslated region consisting of an AUUUUA hexamer flanked by defined U-rich regions constitutes the binding domain for betaARB protein. U to G substitution in the hexamer region attenuates the binding of betaARB protein, whereas U to G substitution of hexamer and flanking U-rich domains abolishes binding of betaARB protein and stabilizes beta2-adrenergic receptor mRNA levels in transfectant clones challenged with either isoproterenol or cyclic AMP. These results demonstrate that binding of betaARB protein to the 20-nucleotide, (A + U)-rich domain mediates the agonist and cyclic AMP-induced mRNA decay of G protein-linked receptors, such as the beta2-adrenergic receptor.