Williamson J R, Raghuraman M K, Cech T R
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, Boulder, Colorado 80309.
Cell. 1989 Dec 1;59(5):871-80. doi: 10.1016/0092-8674(89)90610-7.
We have investigated the structures formed by oligonucleotides composed of two or four repeats of the telomeric sequences from Oxytricha and Tetrahymena. The Oxytricha four-repeat molecule (d(T4G4)4 = Oxy-4) forms structures with increased electrophoretic mobility in nondenaturing gels containing Na+, K+, or Cs+, but not in gels containing Li+ or no added salt. Formation of the folded structure results in protection of a set of dG's from methylation by dimethyl sulfate. Efficient UV-induced cross-links are observed in Oxy-4 and the related sequence from Tetrahymena (d(T2G4)4 = Tet-4), and join thymidine residues in different repeats. Models proposed to account for these data involve G-quartets, hydrogen-bonded structures formed from four guanosine residues in a square-planar array. We propose that the G-quartet structure must be dealt with in vivo by the telomere replication machinery.
我们研究了由来自嗜热四膜虫和游仆虫的端粒序列的两个或四个重复序列组成的寡核苷酸所形成的结构。游仆虫的四重复分子（d(T4G4)4 = Oxy-4）在含有Na+、K+或Cs+的非变性凝胶中形成具有增加的电泳迁移率的结构，但在含有Li+或不添加盐的凝胶中则不然。折叠结构的形成导致一组dG免受硫酸二甲酯的甲基化作用。在Oxy-4和来自嗜热四膜虫的相关序列（d(T2G4)4 = Tet-4）中观察到高效的紫外线诱导交联，并连接不同重复序列中的胸腺嘧啶残基。为解释这些数据而提出的模型涉及G-四联体，即由四个鸟苷残基以正方形平面阵列形式形成的氢键结构。我们提出，G-四联体结构在体内必须由端粒复制机制来处理。
