Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
Nucleic Acids Res. 2012 Oct;40(19):9850-62. doi: 10.1093/nar/gks705. Epub 2012 Jul 25.
MicroRNAs (miRNAs) are small noncoding RNAs that function in literally all cellular processes. miRNAs interact with Argonaute (Ago) proteins and guide them to specific target sites located in the 3'-untranslated region (3'-UTR) of target mRNAs leading to translational repression and deadenylation-induced mRNA degradation. Most miRNAs are processed from hairpin-structured precursors by the consecutive action of the RNase III enzymes Drosha and Dicer. However, processing of miR-451 is Dicer independent and cleavage is mediated by the endonuclease Ago2. Here we have characterized miR-451 sequence and structure requirements for processing as well as sorting of miRNAs into different Ago proteins. Pre-miR-451 appears to be optimized for Ago2 cleavage and changes result in reduced processing. In addition, we show that the mature miR-451 only associates with Ago2 suggesting that mature miRNAs are not exchanged between different members of the Ago protein family. Based on cloning and deep sequencing of endogenous miRNAs associated with Ago1-3, we do not find evidence for miRNA sorting in human cells. However, Ago identity appears to influence the length of some miRNAs, while others remain unaffected.
微小 RNA（miRNAs）是一类小的非编码 RNA，几乎参与了所有细胞过程。miRNAs 通过与 Argonaute（AGO）蛋白相互作用，并引导它们与靶信使 RNA（mRNA）3'非翻译区（3'UTR）的特定靶位点结合，从而导致翻译抑制和加尾诱导的 mRNA 降解。大多数 miRNAs 由发夹结构的前体经 RNase III 酶 Drosha 和 Dicer 的连续作用加工而成。然而，miR-451 的加工不依赖于 Dicer，而是由内切酶 Ago2 介导的切割。在这里，我们对 miR-451 的加工以及 miRNA 向不同 AGO 蛋白分选的序列和结构要求进行了描述。前体 miR-451 似乎是为 Ago2 的切割而优化的，其变化导致加工减少。此外，我们还表明，成熟的 miR-451 仅与 Ago2 结合，这表明成熟的 miRNAs 不会在 AGO 蛋白家族的不同成员之间交换。基于与 Ago1-3 相关的内源性 miRNAs 的克隆和深度测序，我们没有发现人细胞中 miRNA 分选的证据。然而，AGO 的身份似乎影响了一些 miRNA 的长度，而其他 miRNA 则不受影响。
