RNAs that interact with the Fragile X syndrome RNA binding protein FMRP

The Fragile X protein FMRP is an RNA binding protein whose targets are not well known; yet, these RNAs may play an integral role in the disease's etio logy, Using a biotinylated-FMRP affinity resin, we isolated RNAs from the p arietal cortex of a normal adult that bound FMRP, These RNAs were amplified by differential display (DDRT-PCR) and cloned and their identities determi ned. Nine candidate RNAs were isolated; five RNAs, including FMR1 mRNA, enc oded known proteins. Four others were novel. The specificity of binding was demonstrated for each candidate RNA. The domains required for binding a su bset of the RNAs were delineated using FMRP truncation mutant proteins and it was shown that only the KH2 domain was required for binding. Binding occ urred independently of homoribopolymer binding to the C-terminal arginine-g lycine-rich region (RGG box), suggesting that FMRP may bind multiple RNAs s imultaneously. (C) 2000 Academic Press.