Li Ying, Tang Wei, Zhang Li-rong, Zhang Chun-yang
Single-Molecule Detection and Imaging Laboratory, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Guangdong, China.
Mol Biosyst. 2014 Jul;10(7):1757-64. doi: 10.1039/c4mb00066h. Epub 2014 Apr 14.
Fragile X syndrome (FXS) is caused by the loss of expression of fragile X mental retardation protein (FMRP), a selective RNA-binding protein that negatively regulates mRNA substrates. FMRP can regulate the translation via the cross-talk with the miRNA machinery, but the functional association among FMRP, miRNAs and mutual target mRNAs has rarely been studied. In this research, we find that HOXB8 mRNA is a target of FMRP associated with miR-196a-induced silencing, and discover that phosphorylation of FMRP promotes the miR-196a-mediated repression of HOXB8 without affecting the interaction between FMRP and mRNA. We further identify that the FMRP-binding site involved in the miR-196a-mediated repression of HOXB8 locates in the downstream neighbourhood of the miR-196a recognition element in the 3'UTR of HOXB8. Importantly, we reveal that FMRP faces toward the MID domain of AGO2 and interacts with a specific binding pocket (coordination with T544, K533 and K570) in the domain. Our research might provide new insights into both the cross-talk between FMRP and miRNA-mediated regulation of mRNA translation and the molecular pathogenesis of FXS.
脆性X综合征（FXS）是由脆性X智力低下蛋白（FMRP）表达缺失引起的，FMRP是一种选择性RNA结合蛋白，对mRNA底物起负调控作用。FMRP可通过与miRNA机制的相互作用来调节翻译，但FMRP、miRNA和共同靶标mRNA之间的功能关联鲜有研究。在本研究中，我们发现HOXB8 mRNA是与miR-196a诱导沉默相关的FMRP的靶标，并发现FMRP的磷酸化促进了miR-196a介导的HOXB8抑制，而不影响FMRP与mRNA之间的相互作用。我们进一步确定，miR-196a介导的HOXB8抑制中涉及的FMRP结合位点位于HOXB8 3'UTR中miR-196a识别元件的下游附近。重要的是，我们揭示FMRP面向AGO2的MID结构域，并与该结构域中的一个特定结合口袋（与T544、K533和K570配位）相互作用。我们的研究可能为FMRP与miRNA介导的mRNA翻译调控之间的相互作用以及FXS的分子发病机制提供新的见解。
