Kojima-Kita Kanako, Kuramochi-Miyagawa Satomi, Nagamori Ippei, Ogonuki Narumi, Ogura Atsuo, Hasuwa Hidetoshi, Akazawa Takashi, Inoue Norimitsu, Nakano Toru
Department of Pathology, Medical School, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Department of Pathology, Medical School, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; CREST, Japan Science and Technology Agency.
Cell Rep. 2016 Sep 13;16(11):2819-2828. doi: 10.1016/j.celrep.2016.08.027.
During the development of mammalian embryonic germ cells, global demethylation and de novo DNA methylation take place. In mouse embryonic germ cells, two PIWI family proteins, MILI and MIWI2, are essential for the de novo DNA methylation of retrotransposons, presumably through PIWI-interacting RNAs (piRNAs). Although piRNA-associated MIWI2 has been reported to play critical roles in the process, its molecular mechanisms have remained unclear. To identify the mechanism, transgenic mice were produced; they contained a fusion protein of MIWI2 and a zinc finger (ZF) that recognized the promoter region of a type A LINE-1 gene. The ZF-MIWI2 fusion protein brought about DNA methylation, suppression of the type A LINE-1 gene, and a partial rescue of the impaired spermatogenesis of MILI-null mice. In addition, ZF-MIWI2 was associated with the proteins involved in DNA methylation. These data indicate that MIWI2 functions as an effector of de novo DNA methylation of the retrotransposon.
在哺乳动物胚胎生殖细胞发育过程中，会发生全基因组去甲基化和从头DNA甲基化。在小鼠胚胎生殖细胞中，两种PIWI家族蛋白MILI和MIWI2对于逆转座子的从头DNA甲基化至关重要，推测是通过与PIWI相互作用的RNA（piRNA）来实现的。尽管据报道与piRNA相关的MIWI2在该过程中发挥关键作用，但其分子机制仍不清楚。为了确定其机制，制备了转基因小鼠；这些小鼠含有MIWI2与识别A型LINE-1基因启动子区域的锌指（ZF）的融合蛋白。ZF-MIWI2融合蛋白导致DNA甲基化、A型LINE-1基因的抑制以及对MILI基因敲除小鼠受损精子发生的部分挽救。此外，ZF-MIWI2与参与DNA甲基化的蛋白质相关。这些数据表明MIWI2作为逆转座子从头DNA甲基化的效应器发挥作用。
