State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
Proc Natl Acad Sci U S A. 2017 Oct 17;114(42):E8930-E8939. doi: 10.1073/pnas.1710885114. Epub 2017 Oct 2.
Jasmonoyl-isoleucine (JA-Ile), the active form of the plant hormone jasmonate (JA), is sensed by the F-box protein CORONATINE INSENSITIVE 1 (COI1), a component of a functional Skp-Cullin-F-box E3 ubiquitin ligase complex. Sensing of JA-Ile by COI1 rapidly triggers genome-wide transcriptional changes that are largely regulated by the basic helix-loop-helix transcription factor MYC2. However, it remains unclear how the JA-Ile receptor protein COI1 relays hormone-specific regulatory signals to the RNA polymerase II general transcriptional machinery. Here, we report that the plant transcriptional coactivator complex Mediator directly links COI1 to the promoters of MYC2 target genes. MED25, a subunit of the Mediator complex, brings COI1 to MYC2 target promoters and facilitates COI1-dependent degradation of jasmonate-ZIM domain (JAZ) transcriptional repressors. MED25 and COI1 influence each other's enrichment on MYC2 target promoters. Furthermore, MED25 physically and functionally interacts with HISTONE ACETYLTRANSFERASE1 (HAC1), which plays an important role in JA signaling by selectively regulating histone (H) 3 lysine (K) 9 (H3K9) acetylation of MYC2 target promoters. Moreover, the enrichment and function of HAC1 on MYC2 target promoters depend on COI1 and MED25. Therefore, the MED25 interface of Mediator links COI1 with HAC1-dependent H3K9 acetylation to activate MYC2-regulated transcription of JA-responsive genes. This study exemplifies how a single Mediator subunit integrates the actions of both genetic and epigenetic regulators into a concerted transcriptional program.
茉莉酰异亮氨酸（JA-Ile）是植物激素茉莉酸（JA）的活性形式，被 F-box 蛋白 CORONATINE INSENSITIVE 1（COI1）感知，COI1 是一种功能性 Skp-Cullin-F-box E3 泛素连接酶复合物的组成部分。COI1 对 JA-Ile 的感应迅速引发全基因组转录变化，这些变化主要受碱性螺旋-环-螺旋转录因子 MYC2 调控。然而，JA-Ile 受体蛋白 COI1 如何将激素特异性调节信号传递给 RNA 聚合酶 II 通用转录机制仍不清楚。在这里，我们报告植物转录共激活复合物 Mediator 直接将 COI1 与 MYC2 靶基因的启动子连接。Mediator 复合物的亚基 MED25 将 COI1 带到 MYC2 靶启动子，并促进 COI1 依赖的茉莉酸-ZIM 结构域（JAZ）转录阻遏物的降解。MED25 和 COI1 相互影响彼此在 MYC2 靶启动子上的富集。此外，MED25 与 HISTONE ACETYLTRANSFERASE1（HAC1）在物理和功能上相互作用，HAC1 通过选择性调节 MYC2 靶启动子的组蛋白（H）3 赖氨酸（K）9（H3K9）乙酰化，在 JA 信号转导中发挥重要作用。此外，HAC1 在 MYC2 靶启动子上的富集和功能依赖于 COI1 和 MED25。因此，Mediator 的 MED25 界面将 COI1 与 HAC1 依赖性 H3K9 乙酰化联系起来，激活 MYC2 调节的 JA 反应基因的转录。这项研究例证了单个 Mediator 亚基如何将遗传和表观遗传调节剂的作用整合到协调的转录程序中。
