Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA.
Nature. 2013 Apr 11;496(7444):187-92. doi: 10.1038/nature12062. Epub 2013 Apr 3.
Telomerase adds telomeric repeats to chromosome ends using an internal RNA template and a specialized telomerase reverse transcriptase (TERT), thereby maintaining genome integrity. Little is known about the physical relationships among protein and RNA subunits within a biologically functional holoenzyme. Here we describe the architecture of Tetrahymena thermophila telomerase holoenzyme determined by electron microscopy. Six of the seven proteins and the TERT-binding regions of telomerase RNA (TER) have been localized by affinity labelling. Fitting with high-resolution structures reveals the organization of TERT, TER and p65 in the ribonucleoprotein (RNP) catalytic core. p50 has an unanticipated role as a hub between the RNP catalytic core, p75-p19-p45 subcomplex, and the DNA-binding Teb1. A complete in vitro holoenzyme reconstitution assigns function to these interactions in processive telomeric repeat synthesis. These studies provide the first view of the extensive network of subunit associations necessary for telomerase holoenzyme assembly and physiological function.
端粒酶使用内部 RNA 模板和一种特殊的端粒酶逆转录酶（TERT）将端粒重复序列添加到染色体末端，从而维持基因组的完整性。关于生物功能全酶中蛋白质和 RNA 亚基之间的物理关系，人们知之甚少。在这里，我们通过电子显微镜描述了嗜热四膜虫端粒酶全酶的结构。通过亲和标记，已经定位了七个蛋白质中的六个和端粒酶 RNA（TER）的 TERT 结合区域。与高分辨率结构的拟合揭示了 RNP 催化核心中 TERT、TER 和 p65 的组织。p50 出人意料地充当了 RNP 催化核心、p75-p19-p45 亚复合物和 DNA 结合 Teb1 之间的枢纽。完整的体外全酶重建赋予了这些相互作用在进行性端粒重复合成中的功能。这些研究首次提供了端粒酶全酶组装和生理功能所需的广泛亚基关联网络的视图。
