Miwi catalysis is required for piRNA amplification-independent LINE1 transposon silencing
Miwi catalysis is required for piRNA amplification-independent LINE1 transposon silencing
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DOI：
10.1038/nature10672
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发表时间：
2011-12-08
期刊：
影响因子：
64.8
通讯作者：
Pillai, Ramesh S.
中科院分区：
文献类型：
--
作者：
Reuter, Michael;Berninger, Philipp;Pillai, Ramesh S.
重复元件衍生的Piwi相互作用rna (piRNAs)（1,2）在基因组防御机制中与Piwi蛋白Mili（也称为Piwil2）和Miwi2（也称为Piwil4）一起作用，通过小鼠雄性胚胎生殖系DNA甲基化启动转座子沉默。这种沉默依赖于Piwi蛋白参与一个依赖于切片器的piRNA扩增途径，对男性生育能力至关重要（3,4）。Piwi家族的第三个成员Miwi（也称为Piwil1）在特定的出生后生殖细胞中表达，并与一组独特的功能未知的pirna相关（5-7）。在这里，我们证明了Miwi是一个小的rna引导的RNase（切片器），需要广泛的互补才能在体外切割目标。在小鼠中，单点突变破坏其催化活性导致雄性不育，突变的生殖细胞显示LINE1反转录子转录物的积累增加。我们提供了Miwi切片机活性直接切割转座子信使rna的证据，为在种系干细胞中建立转座子沉默后长时间内重复衍生pirna的持续维持提供了解释。此外，我们的研究支持一种依赖于切片器的沉默机制，该机制在没有piRNA扩增的情况下起作用。因此，Piwi蛋白似乎在哺乳动物转座子沉默策略中起着双管齐下的作用：一个在胚胎中促进转录抑制，另一个在出生后加强转录后水平的沉默。
Repetitive-element-derived Piwi-interacting RNAs (piRNAs)(1,2) act together with Piwi proteins Mili (also known as Piwil2) and Miwi2 (also known as Piwil4) in a genome defence mechanism that initiates transposon silencing via DNA methylation in the mouse male embryonic germ line. This silencing depends on the participation of the Piwi proteins in a slicer-dependent piRNA amplification pathway and is essential for male fertility(3,4). A third Piwi family member, Miwi (also known as Piwil1), is expressed in specific postnatal germ cells and associates with a unique set of piRNAs of unknown function(5-7). Here we show that Miwi is a small RNA-guided RNase (slicer) that requires extensive complementarity for target cleavage in vitro. Disruption of its catalytic activity in mice by a single point mutation causes male infertility, and mutant germ cells show increased accumulation of LINE1 retrotransposon transcripts. We provide evidence for Miwi slicer activity directly cleaving transposon messenger RNAs, offering an explanation for the continued maintenance of repeat-derived piRNAs long after transposon silencing is established in germline stem cells. Furthermore, our study supports a slicer-dependent silencing mechanism that functions without piRNA amplification. Thus, Piwi proteins seem to act in a two-pronged mammalian transposon silencing strategy: one promotes transcriptional repression in the embryo, the other reinforces silencing at the post-transcriptional level after birth.