Kolchinskiĭ A M, Vashakidze R P, Preobrazhenskaia O V, Karpov V L, Mirzabekov A D
Mol Biol (Mosk). 1984 Jul-Aug;18(4):1141-50.
Chromatin structure of ribosomal genes from nuclei of Drosophila melanogaster embryos was studied by using micrococcal nuclease cleavage. End-directed labelling with short cloned fragments of the ribosomal repeat was carried out. It shows, that the micrococcal nuclease prefers specific sites in naked DNA, and the pattern of DNA cleavage is essentially conserved when the nuclei are digested. Only minor differences are visible. Hence, there are no specific positions of nucleosomes on the ribosomal repeat. The DNA fragments from the nuclei treated with micrococcal nuclease were electrophoresed, transferred to DBM-paper and hybridized with different probes subcloned from the ribosomal repeat. The non-transcribed spacer and the region of the beginning of transcription are hydrolysed significantly faster than the coding region or inactive ribosomal insertion. The region of NTS and the beginning of transcription do not give normal nucleosomal fragment in the range of 145-185 bp; instead they produce a heterogeneous band 200-280 bp in length even after prolonged digestion. Dinucleosomal fragments are also slightly longer and more heterogeneous than in other parts of the ribosomal repeat. Higher oligomers are similar throughout the ribosomal repeat. We suggest that a hypothetical transcription factor interacts in a way with histones and protects unusual fragments of DNA from digestion.
利用微球菌核酸酶切割技术研究了黑腹果蝇胚胎细胞核中核糖体基因的染色质结构。采用核糖体重复序列的短克隆片段进行末端标记。结果表明，微球菌核酸酶在裸露DNA中倾向于特定位点，并且在消化细胞核时DNA切割模式基本保守，仅可见微小差异。因此，核糖体重复序列上不存在核小体的特定位置。用微球菌核酸酶处理细胞核得到的DNA片段经电泳后转移至DBM纸上，并与从核糖体重复序列亚克隆的不同探针杂交。非转录间隔区和转录起始区域的水解速度明显快于编码区或无活性核糖体插入区域。非转录间隔区（NTS）区域和转录起始区域在145 - 185 bp范围内不会产生正常的核小体片段；相反，即使经过长时间消化，它们也会产生长度为200 - 280 bp的异质条带。双核小体片段也比核糖体重复序列的其他部分略长且更具异质性。整个核糖体重复序列中的高级寡聚体相似。我们推测一种假设的转录因子以某种方式与组蛋白相互作用，并保护异常的DNA片段不被消化。
