Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan.
EMBO J. 2009 Dec 16;28(24):3820-31. doi: 10.1038/emboj.2009.365.
In Drosophila, the PIWI proteins, Aubergine (Aub), AGO3, and Piwi are expressed in germlines and function in silencing transposons by associating with PIWI-interacting RNAs (piRNAs). Recent studies show that PIWI proteins contain symmetric dimethyl-arginines (sDMAs) and that dPRMT5/Capsuleen/DART5 is the modifying enzyme. Here, we show that Tudor (Tud), one of Tud domain-containing proteins, associates with Aub and AGO3, specifically through their sDMA modifications and that these three proteins form heteromeric complexes. piRNA precursor-like molecules are detected in these complexes. The expression levels of Aub and AGO3, along with their degree of sDMA modification, were not changed by tud mutations. However, the population of transposon-derived piRNAs associated with Aub and AGO3 was altered by tud mutations, whereas the total amounts of small RNAs on Aub and AGO3 was increased. Loss of dprmt5 did not change the stability of Aub, but impaired its association with Tud and lowered piRNA association with Aub. Thus, in germline cells, piRNAs are quality-controlled by dPRMT5 that modifies PIWI proteins, in tight association with Tud.
在果蝇中，PIWI 蛋白、Aubergine (Aub)、AGO3 和 Piwi 在生殖系中表达，并通过与 PIWI 相互作用 RNA（piRNAs）结合来沉默转座子。最近的研究表明，PIWI 蛋白含有对称二甲基精氨酸 (sDMA)，而 dPRMT5/Capsuleen/DART5 是修饰酶。在这里，我们表明，Tud 是含有 Tud 结构域的蛋白之一，与 Aub 和 AGO3 特异性地通过它们的 sDMA 修饰结合，并且这三种蛋白形成异源三聚体复合物。在这些复合物中检测到类似 piRNA 前体的分子。尽管 tud 突变不会改变 Aub 和 AGO3 的表达水平及其 sDMA 修饰程度，但与 Aub 和 AGO3 相关的转座子衍生 piRNA 的群体发生了改变，而 Aub 和 AGO3 上的小 RNA 总量增加。dprmt5 的缺失不会改变 Aub 的稳定性，但会损害其与 Tud 的结合，并降低 piRNA 与 Aub 的结合。因此，在生殖细胞中，piRNA 由修饰 PIWI 蛋白的 dPRMT5 进行质量控制，与 Tud 紧密结合。
