Faculty of Chemistry and Biochemistry, Biomolecular NMR Spectroscopy, Ruhr University of Bochum, Universitätsstraße 150, 44780 Bochum, Germany.
Faculty of Chemistry and Biochemistry, Protein Interactions, Ruhr University of Bochum, Universitätsstraße 150, 44780 Bochum, Germany.
Nucleic Acids Res. 2019 Dec 16;47(22):11906-11920. doi: 10.1093/nar/gkz614.
High Mobility Group Protein A1a (HMGA1a) is a highly abundant nuclear protein, which plays a crucial role during embryogenesis, cell differentiation, and neoplasia. Here, we present the first ever NMR-based structural ensemble of full length HMGA1a. Our results show that the protein is not completely random coil but adopts a compact structure consisting of transient long-range contacts, which is regulated by post-translational phosphorylation. The CK2-, cdc2- and cdc2/CK2-phosphorylated forms of HMGA1a each exhibit a different binding affinity towards the PRD2 element of the NFκB promoter. Our study identifies connected regions between phosphorylation sites in the wildtype ensemble that change considerably upon phosphorylation, indicating that these posttranslational modifications sites are part of an electrostatic contact network that alters the structural ensemble by shifting the conformational equilibrium. Moreover, ITC data reveal that the CK2-phosphorylated HMGA1a exhibits a different DNA promoter binding affinity for the PRD2 element. Furthermore, we present the first structural model for AT-hook 1 of HMGA1a that can adopt a transient α-helical structure, which might serve as an additional regulatory mechanism in HMAG1a. Our findings will help to develop new therapeutic strategies against HMGA1a-associated cancers by taking posttranslational modifications into consideration.
高迁移率族蛋白 A1a（HMGA1a）是一种含量丰富的核蛋白，在胚胎发生、细胞分化和肿瘤发生过程中发挥着关键作用。在这里，我们首次呈现了基于 NMR 的全长 HMGA1a 的结构整体。我们的结果表明，该蛋白并非完全无规卷曲，而是采用由瞬时长程接触组成的紧凑结构，这种结构受翻译后磷酸化调控。HMGA1a 的 CK2-、cdc2-和 cdc2/CK2 磷酸化形式对 NFκB 启动子的 PRD2 元件表现出不同的结合亲和力。我们的研究鉴定了野生型整体中磷酸化位点之间的连接区域，这些区域在磷酸化后会发生很大变化，表明这些翻译后修饰位点是静电接触网络的一部分，通过改变构象平衡来改变结构整体。此外，ITC 数据表明，CK2 磷酸化的 HMGA1a 对 PRD2 元件的 DNA 启动子结合亲和力不同。此外，我们提出了 HMGA1a 的 AT 钩 1 的第一个结构模型，该模型可以采用瞬时α-螺旋结构，这可能是 HMAG1a 的另一种额外调节机制。我们的发现将有助于通过考虑翻译后修饰来开发针对 HMGA1a 相关癌症的新治疗策略。
