Decoupling the downstream effects of germline nuclear RNAi reveals that H3K9me3 is dispensable for heritable RNAi and the maintenance of endogenous siRNA-mediated transcriptional silencing in Caenorhabditis elegans.
Decoupling the downstream effects of germline nuclear RNAi reveals that H3K9me3 is dispensable for heritable RNAi and the maintenance of endogenous siRNA-mediated transcriptional silencing in Caenorhabditis elegans.
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DOI：
10.1186/s13072-017-0114-8
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发表时间：
2017
影响因子：
3.9
通讯作者：
Gu SG
中科院分区：
文献类型：
--
作者：
Kalinava N;Ni JZ;Peterman K;Chen E;Gu SG
在C. elegans是一种跨代基因沉默途径，导致H3 K9三甲基化（H3 K9 me 3）和靶基因的转录沉默。外源性双链RNA（dsRNA）或内源性siRNA（endo-siRNA）诱导的H3 K9 me 3对靶位点具有高度特异性，可转代遗传。尽管有这些特征，但H3 K9 me 3在siRNA介导的转录沉默中的作用和天然靶基因沉默状态的遗传尚不清楚。在这项研究中，我们采取了遗传和全基因组相结合的方法来解决这个问题。在这里，我们证明了siRNA介导的H3 K9 me 3需要三种H3 K9组蛋白甲基转移酶的组合活性：MET-2，SET-25和SET-32。set-32单突变体、met-2 set-25双突变体和met-2 set-25;set-32三突变体成年动物在整个基因组中都表现出H3 K9 me 3的显著减少，其中met-2 set-25;set-32突变体蠕虫失去了所有可检测的H3 K9 me 3信号。令人惊讶的是，在天然核RNAi靶点处的高量级H3 K9 me 3的损失对转录沉默状态没有影响。此外，外源dsRNA诱导的转录沉默和在oma-1，一个完善的核RNAi报告基因的遗传RNAi，是完全抵抗H3 K9 me 3的损失。核RNAi介导的H3 K9 me 3在C.线虫需要多种组蛋白甲基转移酶，包括MET-2、SET-25和SET-32。H3 K9 me 3对dsRNA诱导的可遗传RNAi或维持内切siRNA介导的C.优美的我们认为siRNA介导的C. elegans可以通过H3 K9 me 3非依赖性机制来维持。本文的在线版本（doi：10.1186/s13072-017-0114-8）包含补充材料，可供授权用户使用。
Germline nuclear RNAi in C. elegans is a transgenerational gene-silencing pathway that leads to H3K9 trimethylation (H3K9me3) and transcriptional silencing at the target genes. H3K9me3 induced by either exogenous double-stranded RNA (dsRNA) or endogenous siRNA (endo-siRNA) is highly specific to the target loci and transgenerationally heritable. Despite these features, the role of H3K9me3 in siRNA-mediated transcriptional silencing and inheritance of the silencing state at native target genes is unclear. In this study, we took combined genetic and whole-genome approaches to address this question. Here we demonstrate that siRNA-mediated H3K9me3 requires combined activities of three H3K9 histone methyltransferases: MET-2, SET-25, and SET-32. set-32 single, met-2 set-25 double, and met-2 set-25;set-32 triple mutant adult animals all exhibit prominent reductions in H3K9me3 throughout the genome, with met-2 set-25;set-32 mutant worms losing all detectable H3K9me3 signals. Surprisingly, loss of high-magnitude H3K9me3 at the native nuclear RNAi targets has no effect on the transcriptional silencing state. In addition, the exogenous dsRNA-induced transcriptional silencing and heritable RNAi at oma-1, a well-established nuclear RNAi reporter gene, are completely resistant to the loss of H3K9me3. Nuclear RNAi-mediated H3K9me3 in C. elegans requires multiple histone methyltransferases, including MET-2, SET-25, and SET-32. H3K9me3 is not essential for dsRNA-induced heritable RNAi or the maintenance of endo-siRNA-mediated transcriptional silencing in C. elegans. We propose that siRNA-mediated transcriptional silencing in C. elegans can be maintained by an H3K9me3-independent mechanism. The online version of this article (doi:10.1186/s13072-017-0114-8) contains supplementary material, which is available to authorized users.