Methylation regulates the intracellular protein-protein and protein-RNA interactions of FMRP.
FMRP, the fragile X mental retardation protein, is an RNA-binding protein that interacts with approximately 4% of fetal brain mRNA. We have recently shown that a methyltransferase (MT) co-translationally methylates FMRP in vitro and that methylation modulates the ability of FMRP to bind mRNA. Here, we recapitulate these in vitro data in vivo, demonstrating that methylation of FMRP affects its ability to bind to FXR1P and regulate the translation of FMRP target mRNAs. Additionally, using double-label fluorescence confocal microscopy, we identified a subpopulation of FMRP-containing small cytoplasmic granules that are distinguishable from larger stress granules. Using the oxidative-stress induced accumulation of abortive pre-initiation complexes as a measure of the association of FMRP with translational components, we have demonstrated that FMRP associates with ribosomes during initiation and, more importantly, that methylation regulates this process by influencing the ratio of FMRP-homodimer-containing mRNPs to FMRP-FXR1P-heterodimer-containing mRNPs. These data suggest a vital role for methylation in normal FMRP functioning.
Dolzhanskaya
Natalia
N
Biochemical Molecular Neurobiology Laboratory, Department of Molecular Biology, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314, USA.
Merz
George
G
Aletta
John M
JM
Denman
Robert B
RB
D000818:Animals; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000378:metabolism; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007124:Immunoenzyme Techniques; D008745:Methylation; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D012270:Ribosomes / Q000378:metabolism
D004791:Enzyme Inhibitors; D051860:Fragile X Messenger Ribonucleoprotein 1; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C096916:FXR1 protein, human