Phosphorylation of FMRP inhibits association with Dicer.
Fragile X syndrome is caused by an absence of the protein product of the fragile X mental retardation gene (FMR1). The fragile X mental retardation protein (FMRP) is an RNA-binding protein that regulates translation of associated mRNAs; however, the mechanism for this regulation remains unknown. Constitutively, phosphorylated FMRP (P-FMRP) is found associated with stalled untranslating polyribosomes, and translation of at least one mRNA is down-regulated when FMRP is phosphorylated. Based on our hypothesis that translational regulation by P-FMRP is accomplished through association with the microRNA (miRNA) pathway, we developed a phospho-specific antibody to P-FMRP and showed that P-FMRP associates with increased amounts of precursor miRNAs (pre-miRNA) compared with total FMRP. Furthermore, P-FMRP does not associate with Dicer or Dicer-containing complexes in coimmunoprecipitation experiments or in an in vitro capture assay using a P-FMRP peptide sequence bound to agarose beads. These data show that Dicer-containing complexes bind FMRP at amino acids 496-503 and that phosphorylation disrupts this association with a consequent increase in association with pre-miRNAs. In sum, we propose that in addition to regulating translation, phosphorylation of FMRP regulates its association with the miRNA pathway by modulating association with Dicer.
Cheever
Anne
A
Ceman
Stephanie
S
D000818:Animals; D002460:Cell Line; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D012333:RNA, Messenger; D043244:Ribonuclease III / Q000378:metabolism*
D051860:Fragile X Messenger Ribonucleoprotein 1; D035683:MicroRNAs; D012333:RNA, Messenger; D043244:Ribonuclease III