SEQUENCE-SPECIFIC BINDING OF CYTOSOLIC PROTEINS TO A 12 NUCLEOTIDE-SEQUENCE IN THE 5'-UNTRANSLATED REGION OF FMR1 MESSENGER-RNA

The 5' untranslated region of human FMR1 mRNA is highly conserved, inc luding a 26 nucleotide sequence containing a tandem 12 nucleotide repe at of (G/C)CU(C/G)CCGG(G/A)G(G/C)(G/C) which predates the evolutionary divergence between birds and mammals. We show here that this 12 nucle otide sequence in FMR1 mRNA is a specific binding site for small (< 20 kDa) cytosolic proteins of rat brain. Point mutation analysis identif ied two guanine residues in this 12 nucleotide repeat which are essent ial for protein binding. The 12 nucleotide motif sequence was found in the 5'UTR of at least 15 other genes and could be a common target sit e for these cytosolic RNA-binding proteins.