研究发现AGO3和Armitage存在相互作用并同时定位于线粒体

小s(Piwi-interacting RNAs)在抑制转座子活性和维持基因组稳定性起重要作用,但其发生和调控的分子机制仍不清楚。果蝇生殖细胞为研究这一机制提供了良好的模型。果蝇生殖细胞中piRNAs 的发生包括初级加工和次级加工两个过程,其中piRNAs次级加工途径,又称乒乓循环(“Ping-Pong”cycle),经过PIWI家族蛋白(AGO3和AUB)的协同作用,能够使细胞中的piRNAs得到大量扩增。

已有的假说表明,在乒乓循环的过程中,PIWI家族成员AUB和AGO3通过piRNA识别的靶RNA进行靶向剪切,使得piRNAs得到次级循环扩增。但AGO3的核酸内切酶(Slr)活性是否发挥作用以及如何发挥作用一直是领域内有待解决的重要科学问题。

动物研究所陈大华实验室研究发现AGO3的Slicer活性对piRNAs的次级扩增非常重要,AGO3以不依赖Slicer活性的方式抑制AUB:AUB乒乓循环。他们进一步研究发现AGO3的Slicer突变体导致piRNAs初级加工蛋白Armitage的异位表达。作为piRNAs初级加工途径的重要成员,Armitage蛋白通常出现在细胞质和上,但AGO3的Slicer突变体导致Armitage蛋白出现在piRNAs次级加工场所nuage细胞器上。重要的是,研究发现AGO3和Armitage存在相互作用并同时定位于线粒体。

此外,AGO3也与另一种线粒体蛋白Zucchini存在相互作用,由此调控AGO3/Armitage复合体在线粒体与nuage之间动态地穿梭,并在nuage上共同参与AGO3 RISC复合体的组装。该研究提出线粒体和nuage共同调控piRNA的次级加工的观点,为进一步深入理解piRNA的发生的机制提供理论依据。该研究成果于7月21日发表于Journal of Cell 。

原文摘要:

Haidong Huang, Yujing Li,Keith E. Szulwach, Guoqiang Zhang,Peng Jin and Dahua Chen

In Drosophila melanogaster the reciprocal “Ping-Pong” cycle of PIWI-interacting RNA (piRNA)–directed RNA cleavage catalyzed by the endonuclease (or “Slicer”) activities of the PIWI proteins Aubergine (Aub) and Argonaute3 (AGO3) has been proposed to expand the secondary piRNA population. However, the role of AGO3/Aub Slicer activity in piRNA amplification remains to be explored. We show that AGO3 Slicer activity is essential for piRNA amplification and that AGO3 inhibits the homotypic Aub:Aub Ping-Pong process in a Slicer-independent manner. We also find that of an AGO3 Slicer mutant causes ectopic accumulation of Armitage, a key component in the primary piRNA pathway, in the Drosophila melanogaster germline granules known as nuage. AGO3 also coexists and interacts with Armitage in the mitochondrial fraction. Furthermore, AGO3 acts in conjunction with the mitochondria-associated protein Zucchini to control the dynamic subcellular localization of Armitage between mitochondria and nuage in a Slicer-dependent fashion. Collectively, our findings uncover a new mechanism that couples mitochondria with nuage to regulate secondary piRNA amplification.

作者:中科院 点击:次

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