Department of Environmental Toxicology, Lubbock, TX 79409, USA.
The Institute of Environmental and Human Health (TIEHH), Lubbock, TX 79409, USA.
Nucleic Acids Res. 2020 May 21;48(9):4681-4697. doi: 10.1093/nar/gkaa209.
The miRNA pathway has three segments-biogenesis, targeting and downstream regulatory effectors. We aimed to better understand their cellular control by exploring the miRNA-mRNA-targeting relationships. We first used human evolutionarily conserved sites. Strikingly, AGOs 1-3 are all among the top 14 mRNAs with the highest miRNA site counts, along with ANKRD52, the phosphatase regulatory subunit of the recently identified AGO phosphorylation cycle; and the AGO phosphorylation cycle mRNAs share much more than expected miRNA sites. The mRNAs for TNRC6, which acts with AGOs to channel miRNA-mediated regulatory actions onto specific mRNAs, are also heavily miRNA-targeted. In contrast, upstream miRNA biogenesis mRNAs are not, and neither are downstream regulatory effectors. In short, binding site enrichment in miRNA targeting machinery mRNAs, but neither upstream biogenesis nor downstream effector mRNAs, was observed, endowing a cellular capacity for intensive and specific feedback control of the targeting activity. The pattern was confirmed with experimentally determined miRNA-mRNA target relationships. Moreover, genetic experiments demonstrated cellular utilization of this capacity. Thus, we uncovered a capacity for intensive, and specific, feedback-regulation of miRNA targeting activity directly by miRNAs themselves, i.e. segment-specific feedback auto-regulation of miRNA pathway, complementing miRNAs pairing with transcription factors to form hybrid feedback-loop.
miRNA 通路由三个部分组成——生物发生、靶向和下游调节效应器。我们旨在通过探索 miRNA-mRNA-靶向关系来更好地了解它们的细胞控制。我们首先使用了人类进化保守的位点。令人惊讶的是，AGO1-3 都在具有最高 miRNA 位点数的前 14 个 mRNA 之列，与最近发现的 AGO 磷酸化循环的磷酸酶调节亚基ANKRD52一起；并且 AGO 磷酸化循环的 mRNAs 共享的 miRNA 位点比预期的多得多。与 AGO 一起作用将 miRNA 介导的调节作用引导到特定 mRNAs 上的 TNRC6 的 mRNAs 也受到强烈的 miRNA 靶向作用。相比之下，上游 miRNA 生物发生的 mRNAs 没有，下游调节效应器也没有。简而言之，观察到 miRNA 靶向机制 mRNAs 中的结合位点富集，但上游生物发生或下游效应器 mRNAs 没有，赋予了细胞对靶向活性进行密集和特定反馈控制的能力。该模式通过实验确定的 miRNA-mRNA 靶关系得到了证实。此外，遗传实验证明了细胞对这种能力的利用。因此，我们发现了 miRNA 本身对 miRNA 靶向活性进行密集和特定反馈调节的能力，即 miRNA 通路的特定片段反馈自动调节，补充了 miRNA 与转录因子配对形成混合反馈环的功能。
