Dawson D, Herrick G
Cell. 1984 Jan;36(1):171-7. doi: 10.1016/0092-8674(84)90086-2.
The hypotrichous ciliated protozoan Oxytricha fallax has both macronuclei and micronuclei. The short DNA molecules of the macronucleus are terminated with repeats of the octanucleotide C4A4. Micronuclear DNA carries a family of long sequence blocks, which share a consensus restriction map and have homology with the C4A4 repeats. Each block contains a 3 to 6 kb subregion, which is refractory to all restriction enzymes tested and includes the C4A4 homology. We conclude that these refractory sequences are at DNA termini because Sau 3A fragments containing them fail to ligate to form circles, and they are rapidly degraded by Bal 31 nuclease. These terminal C4A4-homologous sequence blocks likely represent micronuclear chromosomal telomeres. Possible relationships between these sequences, internal micronuclear C4A4 repeats, and macronuclear DNA termini are discussed.
寡毛目纤毛虫类的类全列游仆虫（Oxytricha fallax）同时拥有大核和小核。大核的短DNA分子以八核苷酸C4A4的重复序列为末端。小核DNA带有一系列长序列片段，这些片段具有一致的限制性酶切图谱，并且与C4A4重复序列具有同源性。每个片段包含一个3至6 kb的区域，该区域对所有测试的限制性酶均具有抗性，并且包含C4A4同源序列。我们得出结论，这些抗性序列位于DNA末端，因为含有它们的Sau 3A片段无法连接形成环状，并且它们会被Bal 31核酸酶迅速降解。这些末端的C4A4同源序列片段可能代表小核染色体端粒。文中讨论了这些序列、小核内部的C4A4重复序列以及大核DNA末端之间可能存在的关系。
