The Caenorhabditis elegans HEN1 ortholog, HENN-1, methylates and stabilizes select subclasses of germline small RNAs.
The Caenorhabditis elegans HEN1 ortholog, HENN-1, methylates and stabilizes select subclasses of germline small RNAs.
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DOI：
10.1371/journal.pgen.1002617
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发表时间：
2012
期刊：
影响因子：
4.5
通讯作者：
Kim JK
中科院分区：
文献类型：
--
作者：
Billi AC;Alessi AF;Khivansara V;Han T;Freeberg M;Mitani S;Kim JK
小 RNA 通过指导名为 Argonautes 的效应蛋白沉默互补 mRNA，来调节多种生物过程。某些类别的小 RNA 的成熟涉及末端 2'-O-甲基化以防止降解。这种修饰是由保守的 HEN1 RNA 甲基转移酶家族成员催化的。在动物中，Piwi 相互作用 RNA (piRNA) 和一些内源性和外源性小干扰 RNA (siRNA) 被甲基化，而 microRNA 则不然。然而，决定动物 HEN1 底物特异性的机制尚未完全解决。在秀丽隐杆线虫中，尚未研究 HEN1 直向同源物，但有证据表明 piRNA 和一些内源 siRNA 存在甲基化。在这里，我们报告蠕虫 HEN1 直系同源物 HENN-1（线虫的 HEN）是线虫小 RNA 甲基化所必需的。我们的结果表明 piRNA 普遍被 HENN-1 甲基化。相比之下，26G RNA（一类初级内源 siRNA）在雌性种系和胚胎中被甲基化，但在雄性种系中却没有甲基化。有趣的是，26G RNA 的甲基化模式与不同的雄性和雌性种系 Argonaute 的表达相关。此外，雌性种系 Argonaute 的缺失会导致 26G RNA 甲基化的完全缺失。这些发现支持一个模型，其中后生动物小 RNA 的甲基化状态由其结合的 Argonaute 决定。 henn-1 的缺失会导致表型，反映底物小 RNA 的不稳定：靶标 mRNA 的失调、生育力受损和体细胞 RNAi 增强。此外，henn-1突变体对种系基因的RNAi敲低反应减弱，表明HENN-1也可能在典型的RNAi中发挥作用。总之，我们的结果表明 HENN-1 在内源性和外源性基因沉默途径中发挥着广泛的作用，并提供了对 HEN1 底物区分机制和 Argonaute 家族多样性的进一步见解。小RNA充当基因组的哨兵，监管自私遗传元件的活动，调节染色质动态，并微调基因表达。这一点在种系中最为重要，内源性小干扰 RNA (endo-siRNA) 和 Piwi 相互作用 RNA (piRNA) 促进功能性配子的形成并确保可存活、可育的后代。小 RNA 主要通过与称为 Argonautes 的效应蛋白结合来直接抑制互补 mRNA 发挥作用。 HEN1 甲基转移酶可甲基化小 RNA，在这些沉默信号的积累中发挥着关键作用。在这项研究中，我们报告了 26G RNA（一类线虫内切 siRNA）在雄性和雌性种系中存在差异甲基化。源自两种种系的 26G RNA 实际上无法区分，只是它们与进化上不同的阿尔戈英雄相关。我们的数据支持一个模型，其中小RNA的甲基化状态以及因此的稳定性是由相关的Argonaute决定的。因此，允许或禁止甲基化的Argonautes的选择性表达可能代表了调节小RNA周转的新机制。当我们在种系中观察到这种现象时，它可能与指导小 RNA 的遗传特别相关，小 RNA 可以携带子代 DNA 中未编码的信息，这对于持续的跨代基因组监测至关重要。
Small RNAs regulate diverse biological processes by directing effector proteins called Argonautes to silence complementary mRNAs. Maturation of some classes of small RNAs involves terminal 2′-O-methylation to prevent degradation. This modification is catalyzed by members of the conserved HEN1 RNA methyltransferase family. In animals, Piwi-interacting RNAs (piRNAs) and some endogenous and exogenous small interfering RNAs (siRNAs) are methylated, whereas microRNAs are not. However, the mechanisms that determine animal HEN1 substrate specificity have yet to be fully resolved. In Caenorhabditis elegans, a HEN1 ortholog has not been studied, but there is evidence for methylation of piRNAs and some endogenous siRNAs. Here, we report that the worm HEN1 ortholog, HENN-1 (HEN of Nematode), is required for methylation of C. elegans small RNAs. Our results indicate that piRNAs are universally methylated by HENN-1. In contrast, 26G RNAs, a class of primary endogenous siRNAs, are methylated in female germline and embryo, but not in male germline. Intriguingly, the methylation pattern of 26G RNAs correlates with the expression of distinct male and female germline Argonautes. Moreover, loss of the female germline Argonaute results in loss of 26G RNA methylation altogether. These findings support a model wherein methylation status of a metazoan small RNA is dictated by the Argonaute to which it binds. Loss of henn-1 results in phenotypes that reflect destabilization of substrate small RNAs: dysregulation of target mRNAs, impaired fertility, and enhanced somatic RNAi. Additionally, the henn-1 mutant shows a weakened response to RNAi knockdown of germline genes, suggesting that HENN-1 may also function in canonical RNAi. Together, our results indicate a broad role for HENN-1 in both endogenous and exogenous gene silencing pathways and provide further insight into the mechanisms of HEN1 substrate discrimination and the diversity within the Argonaute family. Small RNAs serve as sentinels of the genome, policing activity of selfish genetic elements, modulating chromatin dynamics, and fine-tuning gene expression. Nowhere is this more important than in the germline, where endogenous small interfering RNAs (endo-siRNAs) and Piwi-interacting RNAs (piRNAs) promote formation of functional gametes and ensure viable, fertile progeny. Small RNAs act primarily by associating with effector proteins called Argonautes to direct repression of complementary mRNAs. HEN1 methyltransferases, which methylate small RNAs, play a critical role in accumulation of these silencing signals. In this study, we report that the 26G RNAs, a class of C. elegans endo-siRNAs, are differentially methylated in male and female germlines. 26G RNAs derived from the two germlines are virtually indistinguishable, except that they associate with evolutionarily divergent Argonautes. Our data support a model wherein the methylation status and, consequently, stability of a small RNA are determined by the associated Argonaute. Therefore, selective expression of Argonautes that permit or prohibit methylation may represent a new mechanism for regulating small RNA turnover. As we observe this phenomenon in the germline, it may be particularly pertinent for directing inheritance of small RNAs, which can carry information not encoded in progeny DNA that is essential for continued transgenerational genome surveillance.
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影响因子：
14.9
作者：
Chen C;Ridzon DA;Broomer AJ;Zhou Z;Lee DH;Nguyen JT;Barbisin M;Xu NL;Mahuvakar VR;Andersen MR;Lao KQ;Livak KJ;Guegler KJ
通讯作者：
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影响因子：
14.9
作者：
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DOI：
10.1073/pnas.0906378106
发表时间：
2009-11-03
影响因子：
11.1
作者：
Han, Ting;Manoharan, Arun Prasad;Kim, John K.
通讯作者：
Kim, John K.
影响因子：
64.5
作者：
Foerstemann, Klaus;Horwich, Michael D.;Zamore, Phillip D.
通讯作者：
Zamore, Phillip D.
DOI：
10.1073/pnas.0912632107
发表时间：
2010-02-23
影响因子：
11.1
作者：
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通讯作者：
Cerutti, Heriberto