小柯机器人

日本东京大学Yukihide Tomari研究组发现，Zucchini共有基序决定pre-piRNA产生的机制。该项研究成果于2020年1月29日在线发表在《自然》杂志上。

研究人员表示，长度约为24至31个核苷酸的PIWI相互作用RNA（piRNA）引导PIWI蛋白沉默动物性腺中的转座子，从而确保生育能力。在piRNA的产生过程中，首先PIWI蛋白将与称为pre-pre-piRNA的5'-单磷酸化RNA片段进行装载，然后将其进行内切核酸酶切割以产生pre-piRNA。随后，通过外切酶Trimmer（在小鼠中称为PNLDC1）修剪并被甲基转移酶Hen1（在小鼠中称为HENMT1）对pre-piRNA的3'-末端进行2'-O-甲基化，从而产生成熟的piRNA。核酸内切酶Zucchini（在小鼠中称为MitoPLD）被认为是催化pre-pre-piRNA剪切为pre-piRNA 的主要酶。但是，尚缺乏该模型的直接证据，并且尚不清楚如何产生pre-piRNA。

为了分析pre-piRNA的产生，研究人员建立了Trimmer敲除的蚕细胞系，并得到了一个无细胞的系统，该系统准确地涵盖了Zucchini介导PIWI加载的pre-pre-preRNA切割。研究人员发现pre-piRNA是由平行的Zucchini依赖性和非依赖性机制产生的。Zucchini的切割发生在pre-pre-RNA上过去研究中未知的共有基序上，需要RNA解旋酶Armitage，并伴有pre-piRNA的2'-O-甲基化。相比之下，具有弱Zucchini基序的pre-pre-piRNA的切割是通过下游互补piRNA实现的，从而产生了没有2'-O-甲基化的pre-piRNA。不论内切酶的机制如何，pre-piRNA都会被Trimmer和Hen1加工成熟。这些发现强调了piRNA前体的多重加工过程，从而能够支持稳健和灵活的piRNA生成。

附：英文原文

Title: Zucchini consensus motifs determine the mechanism of pre-piRNA production

Author: Natsuko Izumi, Keisuke Shoji, Yutaka Suzuki, Susumu Katsuma, Yukihide Tomari

Issue&Volume: 2020-01-29

Abstract: PIWI-interacting RNAs (piRNAs) of between approximately 24 and 31 nucleotides in length guide PIWI proteins to silence transposons in animal gonads, thereby ensuring fertility1. In the biogenesis of piRNAs, PIWI proteins are first loaded with 5′-monophosphorylated RNA fragments called pre-pre-piRNAs, which then undergo endonucleolytic cleavage to produce pre-piRNAs1,2. Subsequently, the 3′-ends of pre-piRNAs are trimmed by the exonuclease Trimmer (PNLDC1 in mouse)3,4,5,6 and 2′-O-methylated by the methyltransferase Hen1 (HENMT1 in mouse)7,8,9, generating mature piRNAs. It is assumed that the endonuclease Zucchini (MitoPLD in mouse) is a major enzyme catalysing the cleavage of pre-pre-piRNAs into pre-piRNAs10,11,12,13. However, direct evidence for this model is lacking, and how pre-piRNAs are generated remains unclear. Here, to analyse pre-piRNA production, we established a Trimmer-knockout silkworm cell line and derived a cell-free system that faithfully recapitulates Zucchini-mediated cleavage of PIWI-loaded pre-pre-piRNAs. We found that pre-piRNAs are generated by parallel Zucchini-dependent and -independent mechanisms. Cleavage by Zucchini occurs at previously unrecognized consensus motifs on pre-pre-piRNAs, requires the RNA helicase Armitage, and is accompanied by 2′-O-methylation of pre-piRNAs. By contrast, slicing of pre-pre-piRNAs with weak Zucchini motifs is achieved by downstream complementary piRNAs, producing pre-piRNAs without 2′-O-methylation. Regardless of the endonucleolytic mechanism, pre-piRNAs are matured by Trimmer and Hen1. Our findings highlight multiplexed processing of piRNA precursors that supports robust and flexible piRNA biogenesis.

DOI: 10.1038/s41586-020-1966-9

Source: https://www.nature.com/articles/s41586-020-1966-9

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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