Histone H3 lysine 9 trimethylation is required for suppressing the expression of an embryonically activated retrotransposon in Xenopus laevis.
Histone H3 lysine 9 trimethylation is required for suppressing the expression of an embryonically activated retrotransposon in Xenopus laevis.
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DOI：
10.1038/srep14236
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发表时间：
2015-09-21
影响因子：
4.6
通讯作者：
Miyamoto K
中科院分区：
文献类型：
--
作者：
Herberg S;Simeone A;Oikawa M;Jullien J;Bradshaw CR;Teperek M;Gurdon J;Miyamoto K
基因组中的转座因子在分化的体细胞中通常是沉默的。然而，越来越多的证据表明，其中一些在早期胚胎中被活跃地转录，并且逆转录转座子表达的适当调节对于正常发育是必不可少的。虽然它们的发育调控表达已被证明，但控制反转录转座子在早期胚胎中表达的机制仍不清楚。在这里，我们观察到反转录转座子的动态表达模式，其中10个检测的反转录转座子中有3个（1a 11，λ-奥尔特2-1和xretpos（L））仅在早期胚胎发育期间转录。我们还鉴定了一个含有λ-奥尔特2-1的长末端重复序列（LTR）的转录本，并在早期非洲爪蟾胚胎中显示出与λ-奥尔特2-1相似的表达模式。所有三种反转录转座子都由RNA聚合酶II转录。虽然它们的表达水平在发育过程中下降，但LTR以组蛋白H3赖氨酸4三甲基化为标志。此外，逆转录转座子，特别是λ-奥尔特2-1，在其表达被抑制时富含组蛋白H3赖氨酸9三甲基化（H3 K9 me 3）。过表达赖氨酸特异性脱甲基酶4d可去除爪蟾胚胎中的H3 K9 me 3标记，并抑制原肠胚形成后λ-奥尔特2-1的阻遏。因此，我们的研究表明，H3 K9 me 3是重要的沉默非洲爪蟾发育调控反转录转座子。
Transposable elements in the genome are generally silenced in differentiated somatic cells. However, increasing evidence indicates that some of them are actively transcribed in early embryos and the proper regulation of retrotransposon expression is essential for normal development. Although their developmentally regulated expression has been shown, the mechanisms controlling retrotransposon expression in early embryos are still not well understood. Here, we observe a dynamic expression pattern of retrotransposons with three out of ten examined retrotransposons (1a11, λ-olt 2-1 and xretpos(L)) being transcribed solely during early embryonic development. We also identified a transcript that contains the long terminal repeat (LTR) of λ-olt 2-1 and shows a similar expression pattern to λ-olt 2-1 in early Xenopus embryos. All three retrotransposons are transcribed by RNA polymerase II. Although their expression levels decline during development, the LTRs are marked by histone H3 lysine 4 trimethylation. Furthermore, retrotransposons, especially λ-olt 2-1, are enriched with histone H3 lysine 9 trimethylation (H3K9me3) when their expression is repressed. Overexpression of lysine-specific demethylase 4d removes H3K9me3 marks from Xenopus embryos and inhibits the repression of λ-olt 2-1 after gastrulation. Thus, our study shows that H3K9me3 is important for silencing the developmentally regulated retrotransposon in Xenopus laevis.