Fragile X messenger ribonucleoprotein 1
nucleus
The RNA-binding protein FMRP facilitates the nuclear export of <i>N</i><sup>6</sup>-methyladenosine-containing mRNAs.
<i>N</i><sup>6</sup>-Methyladenosine (m<sup>6</sup>A) 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 m<sup>6</sup>A-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 m<sup>6</sup>A sites on mRNAs. FMRP depletion increased mRNA m<sup>6</sup>A levels in the nucleus. Moreover, the abundance of FMRP targets in the cytoplasm relative to the nucleus was decreased in <i>Fmr1</i>-KO mice, an effect also observed in highly methylated genes. We conclude that FMRP may affect the nuclear export of m<sup>6</sup>A-modified RNA targets.