Research Department of Structural and Molecular Biology, University College London, Darwin Building, Gower Street, London WC1E 6XA, UK.
Macromolecular Structure Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
Nucleic Acids Res. 2019 May 7;47(8):4334-4348. doi: 10.1093/nar/gkz136.
IGF2 mRNA-binding protein 1 (IMP1) is a key regulator of messenger RNA (mRNA) metabolism and transport in organismal development and, in cancer, its mis-regulation is an important component of tumour metastasis. IMP1 function relies on the recognition of a diverse set of mRNA targets that is mediated by the combinatorial action of multiple RNA-binding domains. Here, we dissect the structure and RNA-binding properties of two key RNA-binding domains of IMP1, KH1 and KH2, and we build a kinetic model for the recognition of RNA targets. Our data and model explain how the two domains are organized as an intermolecular pseudo-dimer and that the important role they play in mRNA target recognition is underpinned by the high RNA-binding affinity and fast kinetics of this KH1KH2-RNA recognition unit. Importantly, the high-affinity RNA-binding by KH1KH2 is achieved by an inter-domain coupling 50-fold stronger than that existing in a second pseudo-dimer in the protein, KH3KH4. The presence of this strong coupling supports a role of RNA re-modelling in IMP1 recognition of known cancer targets.
胰岛素样生长因子 2 mRNA 结合蛋白 1（IMP1）是调节生物体发育过程中信使 RNA（mRNA）代谢和运输的关键调控因子，在癌症中，其异常调控是肿瘤转移的重要组成部分。IMP1 的功能依赖于对多种 mRNA 靶标的识别，这是由多个 RNA 结合结构域的组合作用介导的。在这里，我们剖析了 IMP1 的两个关键 RNA 结合结构域 KH1 和 KH2 的结构和 RNA 结合特性，并构建了 RNA 靶标识别的动力学模型。我们的数据和模型解释了两个结构域如何作为分子间的拟二聚体组织，以及它们在 mRNA 靶标识别中所起的重要作用，这是由 KH1KH2-RNA 识别单元的高 RNA 结合亲和力和快速动力学所支撑的。重要的是，KH1KH2 的高亲和力 RNA 结合是通过一种比蛋白质中第二个拟二聚体 KH3KH4 存在的域间耦合强 50 倍的方式实现的。这种强耦合的存在支持了 RNA 重塑在 IMP1 识别已知癌症靶标中的作用。
