Yao M C, Zheng K, Yao C H
Cell. 1987 Mar 13;48(5):779-88. doi: 10.1016/0092-8674(87)90075-4.
Chromosomal breakage occurs at hundreds of specific sites in Tetrahymena, including the two ends of the unique ribosomal RNA genes, during the development of the somatic macronucleus. We have identified a 15-nucleotide sequence that occurs widely in the germinal micronuclear genome and is associated exclusively with chromosomal breakage sites. When copies of this sequence were cloned and analyzed, they were found in all cases to be located at or very near sites of breakage. This general rule is further supported by the observation that in a different site in which a single nucleotide substitution is found within this sequence, no chromosomal breakage occurs. The complete sequence structure of one of the breakage junctions has also been determined in both the germinal DNA and the two somatic DNA termini. This structure reveals that the 15-nucleotide conserved sequence is located within a 54-nucleotide region that is removed following chromosomal breakage.
在体细胞大核的发育过程中，染色体断裂发生在四膜虫的数百个特定位点，包括独特核糖体RNA基因的两端。我们已经鉴定出一个15个核苷酸的序列，它在生殖小核基因组中广泛存在，并且仅与染色体断裂位点相关。当克隆并分析该序列的拷贝时，发现它们在所有情况下都位于断裂位点或非常接近断裂位点。在该序列中发现单个核苷酸取代的另一个位点没有发生染色体断裂，这一观察结果进一步支持了这一普遍规律。还确定了一个断裂连接点在生殖DNA和两个体细胞DNA末端的完整序列结构。该结构表明，15个核苷酸的保守序列位于一个54个核苷酸的区域内，该区域在染色体断裂后被去除。
