Center for Food and Bioconvergence, Seoul National University, Seoul, 08826, Republic of Korea.
Center for Food and Bioconvergence, Seoul National University, Seoul, 08826, Republic of Korea.
Biochem Biophys Res Commun. 2018 Dec 9;507(1-4):437-442. doi: 10.1016/j.bbrc.2018.11.057. Epub 2018 Nov 15.
AtMYB44 has been described in diverse hormonal signaling processes including abscisic acid (ABA)-mediated tolerance to abiotic stress; however, its function as a transcription factor is controversial. AtMYB44 contains the amino acid sequence LSLSL, a putative ETHYLENE-RESPONSIVE ELEMENT BINDING FACTOR-ASSOCIATED AMPHIPHILIC REPRESSION (EAR) motif. In yeast two-hybrid assay, physical interaction between AtMYB44 and a TOPLESS-RELATED (TPR) corepressor was observed, but abolished by mutation of the EAR motif. We performed bimolecular fluorescence complementation assay to confirm their interaction in planta. Chromatin immunoprecipitation assay revealed binding of AtMYB44 to the promoter regions of clade A protein phosphatase 2C (PP2C) genes (e.g., ABI1, ABI2, and HAI1), implying putative targets. Levels of histone H3 acetylation around the promoter regions were markedly lower in AtMYB44-overexpressing (35S:AtMYB44) plants than in wild-type plants. These results suggest that AtMYB44 forms a complex with TPR corepressors and recruits histone deacetylase(s) to suppress PP2C gene transcription in a signal-independent manner.
在多种激素信号转导过程中都描述了 AtMYB44 的作用，包括脱落酸（ABA）介导的非生物胁迫耐受；然而，其作为转录因子的功能存在争议。AtMYB44 含有氨基酸序列 LSLSL，这是一个假定的乙烯响应元件结合因子相关的疏水性抑制（EAR）基序。在酵母双杂交试验中，观察到 AtMYB44 与 TOPLESS-RELATED（TPR）核心抑制子之间存在物理相互作用，但 EAR 基序的突变使其作用消失。我们进行了双分子荧光互补测定以确认它们在植物体内的相互作用。染色质免疫沉淀试验显示 AtMYB44 与 clade A 蛋白磷酸酶 2C（PP2C）基因（如 ABI1、ABI2 和 HAI1）的启动子区域结合，暗示了潜在的靶标。在 AtMYB44 过表达（35S:AtMYB44）植物中，启动子区域周围组蛋白 H3 乙酰化水平明显低于野生型植物。这些结果表明，AtMYB44 与 TPR 核心抑制子形成复合物，并以信号非依赖性方式招募组蛋白脱乙酰酶（s）来抑制 PP2C 基因的转录。
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