Macromolecular Crystallography Laboratory, National Cancer Institute, Frederick, MD, 21702, USA.
Nat Commun. 2019 Jul 12;10(1):3085. doi: 10.1038/s41467-019-11083-2.
DEAD-box helicases (DDXs) regulate RNA processing and metabolism by unwinding short double-stranded (ds) RNAs. Sharing a helicase core composed of two RecA-like domains (D1D2), DDXs function in an ATP-dependent, non-processive manner. As an attractive target for cancer and AIDS treatment, DDX3X and its orthologs are extensively studied, yielding a wealth of biochemical and biophysical data, including structures of apo-D1D2 and post-unwound D1D2:single-stranded RNA complex, and the structure of a D2:dsRNA complex that is thought to represent a pre-unwound state. However, the structure of a pre-unwound D1D2:dsRNA complex remains elusive, and thus, the mechanism of DDX action is not fully understood. Here, we describe the structure of a D1D2 core in complex with a 23-base pair dsRNA at pre-unwound state, revealing that two DDXs recognize a 2-turn dsRNA, each DDX mainly recognizes a single RNA strand, and conformational changes induced by ATP binding unwinds the RNA duplex in a cooperative manner.
DEAD-box 解旋酶（DDXs）通过解开短双链 RNA（dsRNA）来调节 RNA 加工和代谢。DDXs 共享由两个 RecA 样结构域（D1D2）组成的解旋酶核心，以 ATP 依赖的、非连续的方式发挥作用。作为癌症和艾滋病治疗的一个有吸引力的靶点，DDX3X 及其同源物被广泛研究，产生了大量的生化和生物物理数据，包括 apo-D1D2 和展开后 D1D2：单链 RNA 复合物的结构，以及 D2：dsRNA 复合物的结构，该结构被认为代表了预展开状态。然而，预展开的 D1D2：dsRNA 复合物的结构仍然难以捉摸，因此，DDX 作用的机制尚不完全清楚。在这里，我们描述了 D1D2 核心与未展开的 23 碱基对 dsRNA 复合物的结构，揭示了两个 DDX 识别一个 2 转 dsRNA，每个 DDX 主要识别一个单链 RNA，并且 ATP 结合诱导的构象变化以协同的方式解开 RNA 双链。
