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Nuclear RNA export factor variant initiates piRNA-guided co-transcriptional silencing.
The EMBO Journal ( IF 9.4 ) Pub Date : 2019-08-01 , DOI: 10.15252/embj.2019102870
Kensaku Murano 1 , Yuka W Iwasaki 1 , Hirotsugu Ishizu 1 , Akane Mashiko 1, 2 , Aoi Shibuya 1 , Shu Kondo 3 , Shungo Adachi 4 , Saori Suzuki 5 , Kuniaki Saito 3 , Tohru Natsume 4 , Mikiko C Siomi 5 , Haruhiko Siomi 1
Affiliation  

The PIWI-interacting RNA (piRNA) pathway preserves genomic integrity by repressing transposable elements (TEs) in animal germ cells. Among PIWI-clade proteins in Drosophila, Piwi transcriptionally silences its targets through interactions with cofactors, including Panoramix (Panx) and forms heterochromatin characterized by H3K9me3 and H1. Here, we identified Nxf2, a nuclear RNA export factor (NXF) variant, as a protein that forms complexes with Piwi, Panx, and p15. Panx-Nxf2-P15 complex formation is necessary in the silencing by stabilizing protein levels of Nxf2 and Panx. Notably, ectopic targeting of Nxf2 initiates co-transcriptional repression of the target reporter in a manner independent of H3K9me3 marks or H1. However, continuous silencing requires HP1a and H1. In addition, Nxf2 directly interacts with target TE transcripts in a Piwi-dependent manner. These findings suggest a model in which the Panx-Nxf2-P15 complex enforces the association of Piwi with target transcripts to trigger co-transcriptional repression, prior to heterochromatin formation in the nuclear piRNA pathway. Our results provide an unexpected connection between an NXF variant and small RNA-mediated co-transcriptional silencing.

中文翻译:

核 RNA 输出因子变异启动 piRNA 引导的共转录沉默。

PIWI 相互作用 RNA (piRNA) 途径通过抑制动物生殖细胞中的转座元件 (TE) 来保持基因组完整性。在果蝇的 PIWI 进化枝蛋白中,Piwi 通过与 Panoramix (Panx) 等辅因子相互作用,在转录上沉默其靶标,并形成以 H3K9me3 和 H1 为特征的异染色质。在这里,我们鉴定出 Nxf2,一种核 RNA 输出因子 (NXF) 变体,是一种与 Piwi、Panx 和 p15 形成复合物的蛋白质。Panx-Nxf2-P15 复合物的形成对于稳定 Nxf2 和 Panx 的蛋白质水平的沉默是必要的。值得注意的是,Nxf2 的异位靶向以独立于 H3K9me3 标记或 H1 的方式启动目标报告基因的共转录抑制。然而,连续沉默需要HP1a和H1。此外,Nxf2 以 Piwi 依赖性方式直接与目标 TE 转录本相互作用。这些发现提出了一个模型,其中 Panx-Nxf2-P15 复合物强制 Piwi 与目标转录本的关联,以在核 piRNA 途径中异染色质形成之前触发共转录抑制。我们的结果提供了 NXF 变体和小 RNA 介导的共转录沉默之间的意外联系。
更新日期:2019-09-03
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