Dolzhanskaya Natalia, Merz George, Aletta John M, Denman Robert B
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.
J Cell Sci. 2006 May 1;119(Pt 9):1933-46. doi: 10.1242/jcs.02882.
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.
脆性X智力低下蛋白（FMRP）是一种RNA结合蛋白，它与约4%的胎儿脑mRNA相互作用。我们最近发现，一种甲基转移酶（MT）在体外对FMRP进行共翻译甲基化，且甲基化可调节FMRP结合mRNA的能力。在此，我们在体内重现了这些体外实验数据，证明FMRP的甲基化会影响其与FXR1P结合以及调节FMRP靶mRNA翻译的能力。此外，通过双标记荧光共聚焦显微镜，我们鉴定出了一类含有FMRP的小细胞质颗粒亚群，它们与较大的应激颗粒不同。利用氧化应激诱导的流产性起始前复合物积累作为FMRP与翻译组分关联的指标，我们证明FMRP在起始过程中与核糖体相关联，更重要的是，甲基化通过影响含FMRP同型二聚体的mRNA颗粒与含FMRP - FXR1P异二聚体的mRNA颗粒的比例来调节这一过程。这些数据表明甲基化在FMRP正常功能中起着至关重要的作用。
