The RNA-binding protein FMRP facilitates the nuclear export of -methyladenosine-containing mRNAs.

-Methyladenosine (mA) is the most abundant post-transcriptional mRNA modification in eukaryotes and exerts many of its effects on gene expression through reader proteins that bind specifically to mA-containing transcripts. Fragile X mental retardation protein (FMRP), an RNA-binding protein, has previously been shown to affect the translation of target mRNAs and trafficking of mRNA granules. Loss of function of FMRP causes fragile X syndrome, the most common form of inherited intellectual disability in humans. Using HEK293T cells, siRNA-mediated gene knockdown, cytoplasmic and nuclear fractions, RNA-Seq, and LC-MS/MS analyses, we demonstrate here that FMRP binds directly to a collection of mA sites on mRNAs. FMRP depletion increased mRNA mA levels in the nucleus. Moreover, the abundance of FMRP targets in the cytoplasm relative to the nucleus was decreased in -KO mice, an effect also observed in highly methylated genes. We conclude that FMRP may affect the nuclear export of mA-modified RNA targets.