Yi Tingfang, Arthanari Haribabu, Akabayov Barak, Song Huaidong, Papadopoulos Evangelos, Qi Hank H, Jedrychowski Mark, Güttler Thomas, Guo Cuicui, Luna Rafael E, Gygi Steven P, Huang Stephen A, Wagner Gerhard
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Department of Chemistry, Ben-Gurion University of the Negev, Be'er-Sheva 84105, Israel.
Nat Commun. 2015 May 28;6:7194. doi: 10.1038/ncomms8194.
MicroRNA (miRNA) biogenesis and miRNA-guided RNA interference (RNAi) are essential for gene expression in eukaryotes. Here we report that translation initiation factor eIF1A directly interacts with Ago2 and promotes Ago2 activities in RNAi and miR-451 biogenesis. Biochemical and NMR analyses demonstrate that eIF1A binds to the MID domain of Ago2 and this interaction does not impair translation initiation. Alanine mutation of the Ago2-facing Lys56 in eIF1A impairs RNAi activities in human cells and zebrafish. The eIF1A-Ago2 assembly facilitates Dicer-independent biogenesis of miR-451, which mediates erythrocyte maturation. Human eIF1A (heIF1A), but not heIF1A(K56A), rescues the erythrocyte maturation delay in eif1axb knockdown zebrafish. Consistently, miR-451 partly compensates erythrocyte maturation defects in zebrafish with eif1axb knockdown and eIF1A(K56A) expression, supporting a role of eIF1A in miRNA-451 biogenesis in this model. Our results suggest that eIF1A is a novel component of the Ago2-centred RNA-induced silencing complexes (RISCs) and augments Ago2-dependent RNAi and miRNA biogenesis.
微小RNA（miRNA）的生物合成以及miRNA介导的RNA干扰（RNAi）对于真核生物中的基因表达至关重要。在此我们报告，翻译起始因子eIF1A直接与Ago2相互作用，并促进RNAi和miR-451生物合成过程中的Ago2活性。生化和核磁共振分析表明，eIF1A与Ago2的MID结构域结合，且这种相互作用不会损害翻译起始。eIF1A中面向Ago2的赖氨酸56突变为丙氨酸会损害人类细胞和斑马鱼中的RNAi活性。eIF1A-Ago2组装促进了不依赖Dicer的miR-451生物合成，而miR-451介导红细胞成熟。人类eIF1A（heIF1A）而非heIF1A（K56A）可挽救eif1axb基因敲低的斑马鱼中的红细胞成熟延迟。同样，miR-451部分补偿了eif1axb基因敲低且表达eIF1A（K56A）的斑马鱼中的红细胞成熟缺陷，支持了eIF1A在该模型中miRNA-451生物合成中的作用。我们的结果表明，eIF1A是以Ago2为中心的RNA诱导沉默复合体（RISC）的一个新组分，并增强了Ago2依赖性RNAi和miRNA生物合成。
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