The intron in centromeric noncoding RNA facilitates RNAi-mediated formation of heterochromatin.
The intron in centromeric noncoding RNA facilitates RNAi-mediated formation of heterochromatin.
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DOI：
10.1371/journal.pgen.1006606
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发表时间：
2017-02
期刊：
影响因子：
4.5
通讯作者：
Tani T
中科院分区：
文献类型：
--
作者：
Mutazono M;Morita M;Tsukahara C;Chinen M;Nishioka S;Yumikake T;Dohke K;Sakamoto M;Ideue T;Nakayama JI;Ishii K;Tani T
在分裂酵母中，着丝粒异染色质的形成是通过RNA干扰（RNAi）介导的途径诱导的。一些前体mRNA剪接突变体（prp）表现出着丝粒异染色质形成缺陷，表明剪接因子在异染色质形成中起作用，或者该缺陷是由编码RNAi因子的前体mRNA的受损剪接引起的。在本文中，我们证明了剪接因子spPrp16 p在着丝粒处富集，并且与Cid12 p（RNAi途径中的因子）和含内含子的dg ncRNA相关联。有趣的是，去除dg内含子、其剪接位点的突变或用常染色质内含子替换dg内含子显著降低H3K9二甲基化。我们还发现，dg ncRNA的剪接在细胞中受到抑制，其抑制依赖于从转录起始位点到内含子的距离。在其他含内含子的着丝粒ncRNA，dh和反义dg中也观察到无效剪接，并且在RNAi因子存在下抑制反义dg ncRNA的剪接。我们的研究结果表明，保留在着丝粒ncRNA中的内含子作为促进剂，与组装在内含子上的剪接因子合作，并作为招募RNAi因子的平台，在着丝粒异染色质的形成中起作用。着丝粒异染色质的形成是有丝分裂中姐妹染色单体正确分离所必需的。在裂殖酵母中，着丝粒异染色质的形成是通过RNA干扰（RNAi）系统进行的，该系统涉及加工从着丝粒转录的非编码RNA。我们发现着丝粒dg ncRNA中的内含子促进裂殖酵母中着丝粒异染色质的形成。我们发现剪接因子spPrp16 p与RNAi因子和含内含子的dg ncRNA相关。dg内含子的去除或突变显著降低了H3K9二甲基化，表明内含子和相关的剪接因子作为招募RNAi因子的平台。低效率剪接是含内含子的着丝粒ncRNA的标志。这种剪接的抑制似乎对促进异染色质的形成很重要。常染色质区的内含子通过剪接被去除以产生功能性RNA，而着丝粒内含子通过剪接抑制保留在ncRNA中并在基因沉默中发挥作用。我们的发现揭示了内含子在基因表达和异染色质形成的表观遗传调控中的新作用。
In fission yeast, the formation of centromeric heterochromatin is induced through the RNA interference (RNAi)-mediated pathway. Some pre-mRNA splicing mutants (prp) exhibit defective formation of centromeric heterochromatin, suggesting that splicing factors play roles in the formation of heterochromatin, or alternatively that the defect is caused by impaired splicing of pre-mRNAs encoding RNAi factors. Herein, we demonstrate that the splicing factor spPrp16p is enriched at the centromere, and associates with Cid12p (a factor in the RNAi pathway) and the intron-containing dg ncRNA. Interestingly, removal of the dg intron, mutations of its splice sites, or replacement of the dg intron with an euchromatic intron significantly decreased H3K9 dimethylation. We also revealed that splicing of dg ncRNA is repressed in cells and its repression depends on the distance from the transcription start site to the intron. Inefficient splicing was also observed in other intron-containing centromeric ncRNAs, dh and antisense dg, and splicing of antisense dg ncRNA was repressed in the presence of the RNAi factors. Our results suggest that the introns retained in centromeric ncRNAs work as facilitators, co-operating with splicing factors assembled on the intron and serving as a platform for the recruitment of RNAi factors, in the formation of centromeric heterochromatin. Formation of centromeric heterochromatin is required for correct segregation of sister chromatids during mitosis. In fission yeast, formation of heterochromatin at centromeres is performed through the RNA interference (RNAi) system, which involves processing of noncoding RNAs transcribed from the centromeres. We found that the intron in the centromeric dg ncRNAs facilitates formation of centromeric heterochromatin in fission yeast. We showed that the splicing factor spPrp16p associates with the RNAi factor and intron-containing dg ncRNA. Removal of or mutations in the dg intron significantly decreased H3K9 dimethylation, suggesting that the intron and associated splicing factors serve as a platform for recruitment of RNAi factors. Inefficient splicing is a hallmark of intron-containing centromeric ncRNAs. Such repression of splicing seems to be important for facilitation of heterochromatin formation. Introns in euchromatic regions are removed by splicing to generate functional RNAs, whereas centromeric introns are retained in ncRNAs by splicing repression and play roles in gene silencing. Our findings shed light on the novel roles of introns in epigenetic regulation of gene expression and heterochromatin formation.