Gottschling D E, Cech T R
Cell. 1984 Sep;38(2):501-10. doi: 10.1016/0092-8674(84)90505-1.
Oxytricha macronuclear DNA exists as approximately 24 X 10(6) gene-sized molecules terminating with a C4A4 repeat. DNA-protein interactions at the ends of bulk macronuclear molecules were probed with micrococcal nuclease and methidiumpropyl-EDTA X Fe(II) (MPE X Fe[II]). The ends were indirectly labeled by hybridizing with (C4A4)2. Alternatively, a novel method using MPE X FE(II) as a probe and directly labeling the 3' ends with terminal transferase was implemented. A terminal complex involving approximately 100 bp with nucleosomes phased inward from the complex was found to be characteristic of most or all of the ends. Analysis of two specific genes confirmed the pattern and showed that the special structure was on both ends of each molecule. We conclude that a DNA-protein complex involving 100 bp and terminating with the C4A4 repeat can be sufficient to provide the fundamental functions of telomeres, allowing linear DNA replication and conferring stability of linear DNA.
嗜热四膜虫的大核DNA以大约24×10⁶个基因大小的分子形式存在，其末端为C4A4重复序列。用微球菌核酸酶和甲基丙基-EDTA X Fe(II)（MPE X Fe[II]）探测大量大核分子末端的DNA-蛋白质相互作用。通过与（C4A4）₂杂交间接标记末端。另外，实施了一种使用MPE X FE(II)作为探针并用末端转移酶直接标记3'末端的新方法。发现一种涉及约100 bp的末端复合物，核小体从该复合物向内呈阶段性排列，这是大多数或所有末端的特征。对两个特定基因的分析证实了这种模式，并表明每个分子的两端都有这种特殊结构。我们得出结论，一种涉及100 bp并以C4A4重复序列终止的DNA-蛋白质复合物足以提供端粒的基本功能，允许线性DNA复制并赋予线性DNA稳定性。
