RNA介导的DNA甲基化（RdDM）是植物特有的DNA甲基化途径，负责所有类型的从头甲基化。这一过程中的关键蛋白Argonaute 4 (AGO4) 结合siRNA并且与从头DNA甲基转移酶DRM2互作，将小RNA与DNA甲基化这两种表观调控方式关联在了一起。然而，AGO4自身的调控机制及其意义却并不明确。申请人的前期研究鉴定了一个植物特有的组蛋白去乙酰化酶HD2C能与AGO4互作并调控下游的DNA甲基化；同时，抑制泛素化-蛋白酶体途径或HD2C的突变均导致AGO4蛋白含量的明显上升。本项目将研究HD2C调控AGO4的具体机理，包括对AGO4的定位、siRNA的结合、靶标位点的识别、翻译后的泛素化与乙酰化修饰等方面的调控机制。通过解析HD2C和AGO4相互作用的机理，揭示AGO4发挥功能的全新调控方式，并以此促进对小RNA、DNA甲基化和组蛋白乙酰化等不同染色质修饰之间相互作用机制的理解。

RNA directed DNA methylation (RdDM) is a plant-specific DNA methylation pathway, which is responsible for de novo methylation of all DNA contexts. As a key regulator in this pathway, Argonaute 4 (AGO4) binds siRNA and interacts with de novo DNA methyltransferase DRM2, and then guides DRM2 to its targets. Hence, AGO4 connects two different epigenetic regulation pathways, small RNA and DNA methylation together. Nevertheless, how is AGO4 precisely regulated in this process remains largely unknown. My preliminary study identified a plant-specific Histone Deacetylase 2C (HD2C) interacting with AGO4 and regulating DNA methylation. Furthermore, inhibition of Unbiquitin-Proteasome pathway or mutation of HD2C significantly increased AGO4 protein accumulation. This project will investigate how does HD2C regulate the localization, siRNA binding, chromatin targeting, posttranslational ubiquitination and acetylation of AGO4. By studying the HD2C-AGO4 interaction, we sought to reveal novel mechanisms of AGO4 regulation, and facilitate the understanding of interactions between different epigenetic modifications, including small RNA, DNA methylation and histone acetylation. Finally, our research will provide new insights into epigenetic regulation network.