Fajkus J, Kovarík A, Královics R, Bezdĕk M
Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno.
Mol Gen Genet. 1995 Jun 10;247(5):633-8. doi: 10.1007/BF00290355.
We have examined the structure and chromatin organization of telomeres in Nicotiana tabacum. In tobacco the blocks of simple telomeric repeats (TT-TAGGG)n are many times larger than in other plants, e.g., Arabidopsis thaliana or tomato. They are resolved as multiple fragments 60-160 kb in size (in most cases 90-130 kb) on pulsed-field gel electrophoresis (PFGE) of restriction endonuclease-digested DNA. The major subtelomeric repeat of the HRS60 family forms large homogeneous blocks of a basic 180 bp motif having comparable lengths. Micrococcal nuclease (MNase) cleaves tobacco telomeric chromatin into subunits with a short repeat length of 157 +/- 5 bp; the subtelomeric heterochromatin characterized by tandemly repeated sequences of the HRS60 family is cut by MNase with a 180 bp periodicity. The monomeric and dimeric particles of telomeric and subtelomeric chromatin differ in sensitivity to MNase treatment: the telomeric particles are readily digested, producing ladders with a periodicity of 7 bp, while the subtelomeric particles appear to be rather resistant to intranucleosomal cleavage. The results presented show apparent similarities in the organization of telomeric chromatin in higher plants and mammals.
我们研究了烟草端粒的结构和染色质组织。在烟草中，简单端粒重复序列（TT-TAGGG）n的片段比其他植物（如拟南芥或番茄）中的大很多倍。在限制性内切酶消化的DNA的脉冲场凝胶电泳（PFGE）上，它们被解析为大小为60-160 kb的多个片段（大多数情况下为90-130 kb）。HRS60家族的主要亚端粒重复序列形成了具有相当长度的基本180 bp基序的大型均匀片段。微球菌核酸酶（MNase）将烟草端粒染色质切割成重复长度为157 +/- 5 bp的亚基；以HRS60家族串联重复序列为特征的亚端粒异染色质被MNase以180 bp的周期切割。端粒和亚端粒染色质的单体和二聚体颗粒对MNase处理的敏感性不同：端粒颗粒很容易被消化，产生周期为7 bp的梯状条带，而亚端粒颗粒似乎对核小体内切割具有相当的抗性。所呈现的结果表明高等植物和哺乳动物端粒染色质的组织存在明显相似性。
