Department of Chemistry, and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA.
Mol Cell. 2012 Jul 13;47(1):16-26. doi: 10.1016/j.molcel.2012.05.018. Epub 2012 Jun 14.
Telomerase is a ribonucleoprotein complex essential for maintenance of telomere DNA at linear chromosome ends. The catalytic core of Tetrahymena telomerase comprises a ternary complex of telomerase RNA (TER), telomerase reverse transcriptase (TERT), and the essential La family protein p65. NMR and crystal structures of p65 C-terminal domain and its complex with stem IV of TER reveal that RNA recognition is achieved by a combination of single- and double-stranded RNA binding, which induces a 105° bend in TER. The domain is a cryptic, atypical RNA recognition motif with a disordered C-terminal extension that forms an α helix in the complex necessary for hierarchical assembly of TERT with p65-TER. This work provides the first structural insight into biogenesis and assembly of TER with a telomerase-specific protein. Additionally, our studies define a structurally homologous domain (xRRM) in genuine La and LARP7 proteins and suggest a general mode of RNA binding for biogenesis of their diverse RNA targets.
端粒酶是一种核糖核蛋白复合物,对于维持线性染色体末端的端粒 DNA 至关重要。四膜虫端粒酶的催化核心由端粒酶 RNA(TER)、端粒酶逆转录酶(TERT)和必需的 La 家族蛋白 p65 组成的三元复合物构成。p65 C 端结构域及其与 TER 茎 IV 复合物的 NMR 和晶体结构揭示了 RNA 识别是通过单链和双链 RNA 结合的组合来实现的,这导致 TER 发生 105°弯曲。该结构域是一种隐匿的、非典型的 RNA 识别基序,具有无规卷曲的 C 端延伸,在复合物中形成 α 螺旋,对于 TERT 与 p65-TER 的分级组装是必需的。这项工作提供了第一个关于端粒酶特异性蛋白的 TER 生物发生和组装的结构见解。此外,我们的研究在真正的 La 和 LARP7 蛋白中定义了一个结构同源的结构域(xRRM),并提出了一个用于其各种 RNA 靶标生物发生的通用 RNA 结合模式。