Eggless/SETDB1 (Egg), the only essential histone methyltransferase (HMT) in Drosophila, plays a role in gene repression, including piRNA-mediated transposon silencing in the ovaries. Previous studies suggested that Egg is post-translationally modified and showed that Windei (Wde) regulates Egg nuclear localization through protein-protein interaction. Monoubiquitination of mammalian SETDB1 is necessary for the HMT activity. Here, using cultured ovarian somatic cells, we show that Egg is monoubiquitinated and phosphorylated but that only monoubiquitination is required for piRNA-mediated transposon repression. Egg monoubiquitination occurs in the nucleus. Egg has its own nuclear localization signal, and the nuclear import of Egg is Wde-independent. Wde recruits Egg to the chromatin at target gene silencing loci, but their interaction is monoubiquitin-independent. The abundance of nuclear Egg is governed by that of nuclear Wde. These results illuminate essential roles of nuclear monoubiquitination of Egg and the role of Wde in piRNA-mediated transposon repression.

中文翻译：

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Windei和Eggless / SETDB1核单泛素在转座子沉默中的重要作用。

Eggless / SETDB1（Egg）是果蝇中唯一必需的组蛋白甲基转移酶（HMT），在基因抑制中发挥作用，包括在卵巢中介导piRNA介导的转座子沉默。先前的研究表明Egg已被翻译后修饰，并显示Windei（Wde）通过蛋白质-蛋白质相互作用来调节Egg的核定位。哺乳动物SETDB1的单泛素化对于HMT活性是必需的。在这里，使用培养的卵巢体细胞，我们显示鸡蛋被单泛素化和磷酸化，但只有单泛素化是piRNA介导的转座子抑制所必需的。卵单泛素化发生在细胞核中。Egg有其自身的核定位信号，并且Egg的核输入与Wde无关。Wde在目标基因沉默位点募集卵到染色质，但它们之间的相互作用是与单泛素无关的。Egg核的丰度受Wde核的丰度支配。这些结果阐明了Egg核单泛素化的基本作用以及Wde在piRNA介导的转座子阻遏中的作用。