生物谷报道：端粒酶（起稳定线形染色体端部这一重要作用的核糖核蛋白（RNP）组合体）的生物起源是一个健康细胞中的一个重要过程，破坏它们的突变能引起疾病。但是，研究人员对RNP组合体的机制很不了解。最近，哈佛大学庄晓薇教授研究组的Michael Stone等人利用一种单分子方法对端粒酶组合体进行了实时分析，对每个组合步骤的精确顺序进行了分解。他们的结果确定了一个分成不同层次的组合机制，该机制包含两个连续的步骤—由蛋白诱导的RNA折叠，最后是将端粒酶复合物模制成它的功能形状。研究结果发表在最新一期的《nature》杂志上。
庄晓薇研究组研究了一种名为嗜热四膜虫（Tetrahymena thermophila）的单细胞水生生物的端粒酶，因为单细胞生物比更高等的生物结构简单，更加容易控制。
端粒酶主要依靠两种成分来实现其功能：一种名为端粒酶逆转录酶（TERT）的蛋白酶，另一种对TERT起到指导作用的一小段RNA片段。庄解释说：“端粒酶只要这两样东西就可以起作用，但是实际上如果你仅仅把它们简单地放到一起去，它们是不会组装成功能结构的。还需要一些其它的辅助蛋白。”庄的研究组与伯克利Kathleen Collins小组合作，发现第三种分子——一种名为p65的蛋白质促进了端粒酶的组装。 庄及其合作者们利用斯坦福科学家Lubert Stryer首创的荧光共振能量转移检测系统（FRET），实时精确观察到端粒酶一步步进行组装的全过程。
庄晓薇说，下一步他们将研究更高级有机体中的端粒酶，以期最终研究人类的端粒酶组装机制。
FIGURE 1. Telomerase proteins p65 and TERT induce distinct conformational changes in telomerase RNA
a, Full-length telomerase RNA labelled with FRET donor (Cy3) and acceptor (Cy5). RNA molecules were immobilized on a streptavidin-coated surface by a biotin molecule engineered onto an extension of stem II. The interaction sites with p65 (red) and TERT (green) are highlighted20, 24. Inset: telomerase primer extension assay with dye-labelled (L) and unlabelled (U) RNA or without RNA (-). Numbers at the right indicate the number of nucleotides added to generate each product. b, FRET histograms of RNA molecules in the absence of protein (grey bars), the presence of 10 nM p65 (red bars) or 10 nM p65 plus 32 nM TERT1–516 (green bars). A peak at FRET = 0 due to the presence of about 30% of molecules without active Cy5 (Supplementary Fig. 2) was removed from these histograms.
原文出处：
Nature Volume 446 Number 7134
Stepwise protein-mediated RNA folding directs assembly of telomerase ribonucleoprotein p458
Michael D. Stone, Mariana Mihalusova, Catherine M. O'Connor, Ramadevi Prathapam, Kathleen Collins and Xiaowei Zhuang
doi:10.1038/nature05600
First paragraph | Full Text | PDF (321K) | Supplementary information
See also: Editor's summary
作者简介：
Xiaowei Zhuang
Howard Hughes Medical Institute Investigator
Professor of Chemistry and Chemical Biology
Professor of Physics
美国哈佛大学化学与化学生物系： Xiaowei Zhuang 副教授的研究组
【URL】 http://zhuang.harvard.edu/
【研究方向】
1)Fundamental understanding of viral infection
2)Structural dynamics and function RNA and ribonucleoprotein (RNP) enzymes
3)RNA interference and micro RNAs
4)Nano-electronic devices for sensing bio-molecules and bio-pathogens at the single-unit level
【简介】
The major interest of Professor Zhuang and her group is to study complex biological processes at the single molecule (or single working unit) level. They are also interested in developing new imaging techniques to image biological molecules and cells.Understanding fundamental molecular mechanisms underlying biological processes is one of the major goals in modern biology
