Two Piwi proteins, Xiwi and Xili, are expressed in the Xenopus female germline.
Two Piwi proteins, Xiwi and Xili, are expressed in the Xenopus female germline.
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DOI：
10.1261/rna.1422509
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发表时间：
2009-02
期刊：
影响因子：
4.5
通讯作者：
A. Wilczyńska;N. Minshall;J. Armisén;E. Miska;N. Standart
中科院分区：
文献类型：
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作者：
A. Wilczyńska;N. Minshall;J. Armisén;E. Miska;N. Standart
Argonaute超家族是一个庞大的RNA结合蛋白家族，参与由小分子非编码RNA介导的基因调控，其特征是存在PAZ和PIWI结构域。该家族由两个分支组成，即Ago分支和Piwi分支。Piwi蛋白与21 - 30个核苷酸长的Piwi相互作用RNA（piRNAs）结合，这些piRNAs主要定位于转座子和重复序列元件。Piwi/piRNAs是配子发生的重要调节因子，并被认为在转座子沉默、DNA甲基化、转录沉默以及翻译和RNA稳定性的转录后调控中发挥作用。到目前为止，大多数报道都集中在雄性生殖系中的Piwi家族成员上。我们在非洲爪蟾中鉴定出了四种Piwi蛋白，并证明其中两种，即Xiwi1b和Xili，在卵母细胞和早期胚胎中表达。Xiwi1和Xili主要存在于小型的、独立的复合物中，我们没有检测到Piwi蛋白与帽结合复合物之间有显著的相互作用。在Xiwi1和Xili中鉴定出了假定的核定位和核输出信号，这支持了我们的观察结果，即Xiwi1是一种核质蛋白，而Xili不是。此外，通过对小分子RNA进行免疫沉淀，我们确定Xiwi1是一种真正的Piwi蛋白。这些结果表明，Piwi/piRNA通路在翻译受抑制的卵母细胞中是有活性的。这是一个重要的发现，因为非洲爪蟾模型为研究转录后机制提供了一个极好的工具。
The Argonaute superfamily is a large family of RNA-binding proteins involved in gene regulation mediated by small noncoding RNA and characterized by the presence of PAZ and PIWI domains. The family consists of two branches, the Ago and the Piwi clade. Piwi proteins bind to 21-30-nucleotide-long Piwi-interacting RNAs (piRNAs), which map primarily to transposons and repeated sequence elements. Piwi/piRNAs are important regulators of gametogenesis and have been proposed to play roles in transposon silencing, DNA methylation, transcriptional silencing, and/or post-transcriptional control of translation and RNA stability. Most reports to date have concentrated on the Piwi family members in the male germline. We have identified four Piwi proteins in Xenopus and demonstrate that two, namely, Xiwi1b and Xili, are expressed in the oocyte and early embryo. Xiwi1 and Xili are predominantly found in small, separate complexes, and we do not detect significant interaction of Piwi proteins with the cap-binding complex. Putative nuclear localization and export signals were identified in Xiwi1 and Xili, supporting our observation that Xiwi1, but not Xili, is a nucleo-cytoplasmic protein. Furthermore, by immunoprecipitation of small RNAs, we establish Xiwi1 as a bona fide Piwi protein. These results suggest that the Piwi/piRNA pathway is active in translationally repressed oocytes. This is a significant finding as the Xenopus model provides an excellent tool to study post-transcriptional mechanisms.