Petracek M E, Lefebvre P A, Silflow C D, Berman J
Department of Plant Biology, University of Minnesota, Saint Paul 55108.
Proc Natl Acad Sci U S A. 1990 Nov;87(21):8222-6. doi: 10.1073/pnas.87.21.8222.
We have isolated telomeric DNA and telomere-associated sequences from Chlamydomonas reinhardtii. The terminal telomere sequences of the green alga Chlamydomonas are composed of (TTTTAGGG)n repeats that are similar, but not identical, to those of the higher plant Arabidopsis thaliana. We demonstrate that these repeats are telomeric by their preferential sensitivity to nuclease Bal-31 digestion, their similarity to A. thaliana telomeres, their orientation relative to the end of the chromosome, and the methods used for their isolation. Five independent telomere clones were isolated, and three of these clones include closely related telomere-associated sequences. One of these telomere-associated sequences hybridizes to a number of genomic fragments sensitive to digestion with the exonuclease Bal-31. Like telomere sequences from other organisms, the C. reinhardtii telomeres display a bias for guanine and thymine nucleotides on the 3'-end strand. However, the sequence of Chlamydomonas telomeres is more A + T-rich than any other known telomere sequence. We propose that the common feature of all known telomere is the frequent occurrence of tracts of three or more adjacent guanine residues.
我们从莱茵衣藻中分离出了端粒DNA和端粒相关序列。绿藻莱茵衣藻的末端端粒序列由(TTTTAGGG)n重复序列组成，这些重复序列与高等植物拟南芥的端粒序列相似，但并不完全相同。我们通过它们对核酸酶Bal-31消化的优先敏感性、与拟南芥端粒的相似性、它们相对于染色体末端的方向以及用于分离它们的方法，证明了这些重复序列是端粒序列。分离出了五个独立的端粒克隆，其中三个克隆包含密切相关的端粒相关序列。这些端粒相关序列之一与许多对外切核酸酶Bal-31消化敏感的基因组片段杂交。与其他生物的端粒序列一样，莱茵衣藻的端粒在3'-末端链上对鸟嘌呤和胸腺嘧啶核苷酸有偏好。然而，衣藻端粒的序列比任何其他已知的端粒序列富含更多的A+T。我们提出，所有已知端粒的共同特征是频繁出现三个或更多相邻鸟嘌呤残基的片段。
