Many proteins, including DICER1 and hAgo2, are involved in the biogenesis of microRNAs (miRNAs). Whether hAgo2 regulates DICER1 expression is unknown. Exogenously overexpressed hAgo2 suppressed DICER1 expression at the levels of both protein and mRNA, and the reduction in hAgo2 expression enhanced DICER1 expression. Precursor miRNA processing mediated by DICER1 was also modulated by hAgo2. However, hAgo2 protein did not suppress DICER1 promoter activity. Therefore, hAgo2 protein probably regulates DICER1 expression at the posttranscriptional level. Indeed, hAgo2 protein inhibited the reporter assay of the DICER1 mRNA 3′ untranslated region (3′-UTR). Previous reports have demonstrated that miRNAs (e.g., let-7 and miR-103/107) inhibited DICER1 expression posttranscriptionally. However, hAgo2 still suppressed DICER1 expression in the cells depleted of these miRNAs. Moreover, the reporter activities of the DICER1 mRNA 3′-UTR without these miRNA binding sites were still suppressed by hAgo2. Therefore, in addition to an miRNA-dependent pathway, hAgo2 can also modulate DICER1 expression through an miRNA-independent mechanism. Downregulation of DICER1 expression was further proven to be dependent on both hAgo2 and AUF1 proteins. Interactions of hAgo2 and AUF1 proteins were demonstrated by the coimmunoprecipitation assay. As expected, hAgo2 could not suppress the DICER1 mRNA 3′-UTR reporter with a mutation in the potential AUF1-binding site. Thus, downregulation of DICER1 expression through the 3′-UTR requires both hAgo2 and AUF1.

中文翻译：

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hAgo2对DICER1表达的MicroRNA依赖性调节。

许多蛋白质，包括DICER1和hAgo2，都参与了microRNA（miRNA）的生物合成。hAgo2是否调节DICER1表达尚不清楚。外源性过表达的hAgo2在蛋白质和mRNA的水平上均抑制了DICER1的表达，而hAgo2表达的降低则增强了DICER1的表达。由DICER1介导的前体miRNA加工也受到hAgo2的调控。但是，hAgo2蛋白不能抑制DICER1启动子活性。因此，hAgo2蛋白可能在转录后水平上调节DICER1的表达。实际上，hAgo2蛋白抑制了DICER1 mRNA 3'非翻译区（3'-UTR）的报告基因检测。先前的报道表明，miRNA（例如let-7和miR-103 / 107）在转录后抑制DICER1表达。然而，hAgo2仍然抑制了这些miRNA耗尽的细胞中DICER1的表达。而且，记者的活动没有这些miRNA结合位点的DICER1 mRNA 3'-UTR仍被hAgo2抑制。因此，除了miRNA依赖性途径，hAgo2还可以通过非miRNA依赖性机制调节DICER1表达。进一步证明DICER1表达的下调同时依赖于hAgo2和AUF1蛋白。通过共免疫沉淀试验证明了hAgo2和AUF1蛋白的相互作用。不出所料，hAgo2不能抑制DICER1 mRNA 3'-UTR报告基因的潜在AUF1结合位点发生突变。因此，通过3'-UTR下调DICER1表达需要hAgo2和AUF1。