Department of Biochemistry, University of Zurich, Zurich, Switzerland.
Department of Oncology, McGill University, Montreal, QC, Canada.
EMBO J. 2018 Apr 3;37(7). doi: 10.15252/embj.201797869. Epub 2018 Mar 6.
The LSM domain-containing protein LSM14/Rap55 plays a role in mRNA decapping, translational repression, and RNA granule (P-body) assembly. How LSM14 interacts with the mRNA silencing machinery, including the eIF4E-binding protein 4E-T and the DEAD-box helicase DDX6, is poorly understood. Here we report the crystal structure of the LSM domain of LSM14 bound to a highly conserved C-terminal fragment of 4E-T. The 4E-T C-terminus forms a bi-partite motif that wraps around the N-terminal LSM domain of LSM14. We also determined the crystal structure of LSM14 bound to the C-terminal RecA-like domain of DDX6. LSM14 binds DDX6 via a unique non-contiguous motif with distinct directionality as compared to other DDX6-interacting proteins. Together with mutational and proteomic studies, the LSM14-DDX6 structure reveals that LSM14 has adopted a divergent mode of binding DDX6 in order to support the formation of mRNA silencing complexes and P-body assembly.
LSM 结构域包含蛋白 LSM14/Rap55 在 mRNA 去帽、翻译抑制和 RNA 颗粒（P 体）组装中发挥作用。然而，LSM14 如何与包括 eIF4E 结合蛋白 4E-T 和 DEAD 盒解旋酶 DDX6 在内的 mRNA 沉默机制相互作用，目前还知之甚少。在这里，我们报告了 LSM14 的 LSM 结构域与 4E-T 的高度保守 C 末端片段结合的晶体结构。4E-T C 末端形成一个二部分基序，环绕 LSM14 的 N 端 LSM 结构域。我们还确定了 LSM14 与 DDX6 的 C 端 RecA 样结构域结合的晶体结构。与其他与 DDX6 相互作用的蛋白质相比，LSM14 通过独特的非连续基序与 DDX6 结合，方向不同。结合突变和蛋白质组学研究，LSM14-DDX6 结构揭示了 LSM14 采用了一种不同的结合 DDX6 的方式，以支持 mRNA 沉默复合物和 P 体组装的形成。
