AU-rich elements (AREs) affect mRNA stability. AREs are binding sites for certain proteins that either stabilize or destabilize the bound mRNA. (a) mRNA transcribed from the β-globin gene is stable for about 10 hours. (b) When a single AT-rich ARE sequence is introduced into the globin gene, such as that derived from the GM-CSF gene, mRNA stability is greatly reduced. (c) When a GC-rich sequence is introduced into the gene, mRNA stability is restored.