METHIONINE ADENOSYLTRANSFERASE4 Mediates DNA and Histone Methylation
METHIONINE ADENOSYLTRANSFERASE4 Mediates DNA and Histone Methylation
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蛋氨酸腺苷转移酶 4 介导 DNA 和组蛋白甲基化
DOI：
10.1104/pp.18.00183
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发表时间：
2018-06-01
期刊：
影响因子：
7.4
通讯作者：
Gong, Zhizhong
中科院分区：
文献类型：
--
作者：
Meng, Jingjing;Wang, Lishuan;Gong, Zhizhong
DNA 和组蛋白甲基化共同调节动物和植物中的异染色质形成和基因沉默。为了确定参与维持基因沉默的因素，我们对在转基因拟南芥 (Arabidopsis thaliana) 系 L119 中释放沉默转基因 Pro35S::新霉素磷酸转移酶 II 的突变体进行了正向遗传筛选。我们鉴定了 MAT4/SAMS3/MTO3/AT3G17390，它编码蛋氨酸 (Met) 腺苷转移酶 4 (MAT4)/S-腺苷-Met 合成酶 3，催化一碳代谢循环中 S-腺苷-Met (SAM) 的合成。 mat4 主要降低 CHG 和 CHH DNA 甲基化和组蛋白 H3K9me2 并重新激活某些沉默的转座子。外源添加 SAM 部分挽救了 mat4 的表观遗传缺陷。 mat4 中的 SAM 含量和 DNA 甲基化比其他三个 mat 突变体中减少得更多。 CRISPR/Cas9 产生的 MAT4 敲除突变是致命的，表明 MAT4 是拟南芥中的必需基因。 MAT1、2 和 4 蛋白在体外测定中表现出几乎相同的活性，而 MAT3 表现出更高的活性。驱动 MAT1、2 和 3 cDNA 的天然 MAT4 启动子与 mat4 突变体互补。然而，大多数携带驱动 MAT4 cDNA 的天然 MAT1、2 和 3 启动子的 mat4 转基因系并不补充 mat4 突变体，因为它们在幼苗中的表达较低。遗传分析表明，mat1mat4 双突变体矮化，mat2mat4 双突变体无法存活，而 mat1mat2 显示正常生长和育性。这些结果表明 MAT4 在 SAM 产生、植物生长和发育中发挥着主导作用。我们的研究结果提供了代谢和表观遗传调控之间协同作用的直接证据。
DNA and histone methylation coregulate heterochromatin formation and gene silencing in animals and plants. To identify factors involved in maintaining gene silencing, we conducted a forward genetic screen for mutants that release the silenced transgene Pro35S::NEOMYCIN PHOSPHOTRANSFERASE II in the transgenic Arabidopsis (Arabidopsis thaliana) line L119. We identified MAT4/SAMS3/MTO3/AT3G17390, which encodes methionine (Met) adenosyltransferase 4 (MAT4)/S-adenosyl-Met synthetase 3 that catalyzes the synthesis of S-adenosyl-Met (SAM) in the one-carbon metabolism cycle. mat4 mostly decreases CHG and CHH DNA methylation and histone H3K9me2 and reactivates certain silenced transposons. The exogenous addition of SAM partially rescues the epigenetic defects of mat4. SAM content and DNA methylation were reduced more in mat4 than in three other mat mutants. MAT4 knockout mutations generated by CRISPR/Cas9 were lethal, indicating that MAT4 is an essential gene in Arabidopsis. MAT1, 2, and 4 proteins exhibited nearly equal activity in an in vitro assay, whereas MAT3 exhibited higher activity. The native MAT4 promoter driving MAT1, 2, and 3 cDNA complemented the mat4 mutant. However, most mat4 transgenic lines carrying native MAT1, 2, and 3 promoters driving MAT4 cDNA did not complement the mat4 mutant because of their lower expression in seedlings. Genetic analyses indicated that the mat1mat4 double mutant is dwarfed and the mat2mat4 double mutant was nonviable, while mat1mat2 showed normal growth and fertility. These results indicate that MAT4 plays a predominant role in SAM production, plant growth, and development. Our findings provide direct evidence of the cooperative actions between metabolism and epigenetic regulation.