Lian Teng-Fei, Xu Yong-Ping, Li Lan-Fen, Su Xiao-Dong
State Key Laboratory of Protein and Plant Gene Research and Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China.
State Key Laboratory of Protein and Plant Gene Research and Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China.
Cell Rep. 2017 May 16;19(7):1334-1342. doi: 10.1016/j.celrep.2017.04.057.
Jasmonates (JAs) are essential plant hormones that play important roles in the regulation of plant growth and the response to environmental stress. In the JA signaling pathway, the core transcription factors are a class of basic helix-loop-helix (bHLH) proteins, including MYC2, MYC3, and MYC4, that have different regulatory capacities. Here, we report the 2.7 Å crystal structure of the MYC2 bHLH domain complexed with G-box DNA, showing a cis-tetrameric structure. Biochemical assays confirmed that full-length MYC2 forms a stable homo-tetramer both in solution and in DNA-bound states, whereas MYC3 forms only a homodimer. Isothermal titration calorimetry (ITC) assays demonstrated that tetramerization enhanced DNA binding affinity, and fluorescence resonance energy transfer (FRET) assay indicated DNA looping potential of tetrameric MYC2. Luciferase assay further confirmed the importance of tetramerization in transcriptional regulation. Our studies provide a mechanistic explanation for the regulatory differences of MYC transcription factors.
茉莉酸类物质（JAs）是重要的植物激素，在植物生长调节和对环境胁迫的响应中发挥重要作用。在茉莉酸信号通路中，核心转录因子是一类基本的螺旋-环-螺旋（bHLH）蛋白，包括MYC2、MYC3和MYC4，它们具有不同的调控能力。在此，我们报道了与G-盒DNA复合的MYC2 bHLH结构域的2.7埃晶体结构，显示出顺式四聚体结构。生化分析证实，全长MYC2在溶液中和与DNA结合的状态下均形成稳定的同源四聚体，而MYC3仅形成同源二聚体。等温滴定量热法（ITC）分析表明，四聚化增强了DNA结合亲和力，荧光共振能量转移（FRET）分析表明四聚体MYC2具有DNA环化潜力。荧光素酶分析进一步证实了四聚化在转录调控中的重要性。我们的研究为MYC转录因子的调控差异提供了机制解释。
