Schuh Gabrielle M, Maschhoff Katharine R, Minor Annastasia, Hu Wenqian
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
RNA. 2025 May 16;31(6):772-780. doi: 10.1261/rna.080426.125.
Argonaute (AGO) proteins are critical regulators of gene expression. Of the four AGOs in mammals, AGO1 and AGO2 are expressed in mouse embryonic stem cells (mESCs). These two proteins have opposing functions in controlling mESCs' fate decisions between pluripotency and differentiation. AGO2 promotes differentiation predominantly via the let-7 microRNAs, whereas AGO1 maintains pluripotency via modulating protein folding independent of small RNAs. These recent findings raise the question of whether and how these two AGOs are mutually regulated in mESCs. Here, using loss-of-function and gain-of-function approaches, we show that AGO2 represses the expression of mRNA via a conserved let-7-microRNA-binding site in its 3' UTR. Mutating this binding site at the endogenous locus abolishes the AGO2-mediated repression of mRNA and compromises the exit pluripotency of mESCs. These results indicate that the posttranscriptional regulation of AGO1 by AGO2 and let-7 microRNAs is important for stem cell differentiation, but also reveal a regulatory mechanism between the two AGO paralogs with opposing functions in controlling stem cell fate decisions.
Argonaute（AGO）蛋白是基因表达的关键调节因子。在哺乳动物的四种AGO蛋白中，AGO1和AGO2在小鼠胚胎干细胞（mESCs）中表达。这两种蛋白在控制mESCs在多能性和分化之间的命运决定方面具有相反的功能。AGO2主要通过let-7微小RNA促进分化，而AGO1通过独立于小RNA调节蛋白质折叠来维持多能性。这些最新发现提出了一个问题，即这两种AGO蛋白在mESCs中是否以及如何相互调节。在这里，我们使用功能丧失和功能获得方法表明，AGO2通过其3'UTR中一个保守的let-7微小RNA结合位点抑制mRNA的表达。在内源位点突变该结合位点可消除AGO2介导的mRNA抑制，并损害mESCs退出多能性的能力。这些结果表明，AGO2和let-7微小RNA对AGO1的转录后调节对干细胞分化很重要，但也揭示了在控制干细胞命运决定中具有相反功能的两个AGO旁系同源物之间的调节机制。
