Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0314 United States.
Biochemistry. 2022 Jun 21;61(12):1199-1212. doi: 10.1021/acs.biochem.2c00228. Epub 2022 Jun 2.
The fragile X proteins (FXPs) are a family of RNA-binding proteins that regulate mRNA translation to promote proper neural development and cognition in mammals. Of particular interest to researchers is the fragile X mental retardation protein (FMRP), as its absence leads to a neurodevelopmental disorder: fragile X syndrome (FXS), the leading monogenetic cause of autism spectrum disorders. A primary focus of research has been to determine mRNA targets of the FXPs in vivo through pull-down techniques, and to validate them through in vitro binding studies; another approach has been to perform in vitro selection experiments to identify RNA sequence and structural targets. These mRNA targets can be further investigated as potential targets for FXS therapeutics. The most established RNA structural target of this family of proteins is the G-quadruplex. In this article, we report a 99 nucleotide RNA target that is bound by all three FXPs with nanomolar equilibrium constants. Furthermore, we determined that the last 102 amino acids of FMRP, which includes the RGG motif, were necessary and sufficient to bind this RNA target. To the best of our knowledge, this is one of only a few examples of non-G-quadruplex, non-homopolymer RNAs bound by the RGG motif/C-termini of FMRP.
脆性 X 蛋白（FXPs）是一组 RNA 结合蛋白，可调节 mRNA 翻译，促进哺乳动物的正常神经发育和认知。研究人员特别关注脆性 X 智力迟钝蛋白（FMRP），因为其缺失会导致神经发育障碍：脆性 X 综合征（FXS），这是自闭症谱系障碍的主要单基因病因。研究的主要重点是通过下拉技术确定体内 FXPs 的 mRNA 靶标，并通过体外结合研究对其进行验证；另一种方法是进行体外选择实验以鉴定 RNA 序列和结构靶标。这些 mRNA 靶标可以进一步作为 FXS 治疗的潜在靶标进行研究。该蛋白家族最成熟的 RNA 结构靶标是 G-四链体。在本文中，我们报告了一个由所有三个 FXPs 以纳摩尔平衡常数结合的 99 个核苷酸 RNA 靶标。此外，我们确定了 FMRP 的最后 102 个氨基酸，包括 RGG 基序，对于结合该 RNA 靶标是必需且充分的。据我们所知，这是 RGG 基序/FMRP C 末端结合的少数非 G-四链体、非均聚物 RNA 之一。
