Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K.
Biochem J. 2024 Nov 6;481(21):1535-1556. doi: 10.1042/BCJ20240248.
Myc proteins are transcription factors crucial for cell proliferation. They have a C-terminal domain that mediates Max and DNA binding, and an N-terminal disordered region culminating in the transactivation domain (TAD). The TAD participates in many protein-protein interactions, notably with kinases that promote stability (Aurora-A) or degradation (ERK1, GSK3) via the ubiquitin-proteasome system. We probed the structure, dynamics and interactions of N-myc TAD using nuclear magnetic resonance (NMR) spectroscopy following its complete backbone assignment. Chemical shift analysis revealed that N-myc has two regions with clear helical propensity: Trp77-Glu86 and Ala122-Glu132. These regions also have more restricted ps-ns motions than the rest of the TAD, and, along with the phosphodegron, have comparatively high transverse (R2) 15N relaxation rates, indicative of slower timescale dynamics and/or chemical exchange. Collectively these features suggest differential propensities for structure and interaction, either internal or with binding partners, across the TAD. Solution studies on the interaction between N-myc and Aurora-A revealed a previously uncharacterised binding site. The specificity and kinetics of sequential phosphorylation of N-myc by ERK1 and GSK3 were characterised using NMR and resulted in no significant structural changes outside the phosphodegron. When the phosphodegron was doubly phosphorylated, N-myc formed a robust interaction with the Fbxw7-Skp1 complex, but mapping the interaction by NMR suggests a more extensive interface. Our study provides foundational insights into N-myc TAD dynamics and a backbone assignment that will underpin future work on the structure, dynamics, interactions and regulatory post-translational modifications of this key oncoprotein.
Myc 蛋白是细胞增殖所必需的转录因子。它们具有一个 C 端结构域,介导 Max 和 DNA 结合,以及一个 N 端无序区域,最终形成转录激活结构域(TAD)。TAD 参与许多蛋白质-蛋白质相互作用,特别是与通过泛素-蛋白酶体系统促进稳定性(Aurora-A)或降解(ERK1、GSK3)的激酶。我们使用核磁共振(NMR)光谱法探测了 N- myc TAD 的结构、动力学和相互作用,方法是在其完整的骨架分配后进行。化学位移分析表明,N-myc 有两个具有明显螺旋倾向的区域:Trp77-Glu86 和 Ala122-Glu132。这些区域的 ps-ns 运动也比 TAD 的其余部分受到更严格的限制,与磷酸化降解区一起,具有相对较高的横向(R2)15N 弛豫率,表明较慢的时间尺度动力学和/或化学交换。这些特征共同表明,在 TAD 中,无论是内部还是与结合伙伴之间,结构和相互作用的倾向存在差异。在 N-myc 与 Aurora-A 之间相互作用的溶液研究中,发现了一个以前未被表征的结合位点。通过 NMR 对 ERK1 和 GSK3 对 N-myc 的顺序磷酸化的特异性和动力学进行了表征,结果除了磷酸化降解区之外,没有明显的结构变化。当磷酸化降解区被双磷酸化时,N-myc 与 Fbxw7-Skp1 复合物形成了一个稳健的相互作用,但通过 NMR 映射相互作用表明存在更广泛的界面。我们的研究为 N-myc TAD 动力学提供了基础见解,并为该关键癌蛋白的结构、动力学、相互作用和调节翻译后修饰的未来工作提供了骨架分配。