Division of Plant Industry, Commonwealth Scientific and Industrial Research Organisation, P.O. Box 1600, Canberra City, ACT, Australia.
Proc Natl Acad Sci U S A. 1981 Jul;78(7):4490-4. doi: 10.1073/pnas.78.7.4490.
A highly repeated DNA sequence has been isolated from the maize genome as a satellite in actinomycin D/CsCl gradients. By using maize stocks differing in their heterochromatin content we have established that the sequence is a major constituent of one class of heterochromatin, knob heterochromatin, which can occur at 23 locations in the chromosome complement. The repeating unit, of 185 base pairs, has been cloned in plasmid pBR322 and its nucleotide sequence has been determined. The presence of this DNA sequence in knob heterochromatin and its absence from centromeric, nucleolar, and B chromosome heterochromatin parallels the cytogenetic differentiation previously described for these classes of heterochromatin in maize. Because knob heterochromatin has a distinctive cytological appearance and is unique in showing neocentric activity at meiosis, its association with a particular repeated DNA sequence may reflect a functional role for the sequence in the cell cycle.
已从玉米基因组中分离出一种高度重复的 DNA 序列，作为放线菌素 D/CsCl 梯度中的卫星。通过使用在异染色质含量上存在差异的玉米品系，我们已经证实该序列是一类异染色质——结构异染色质的主要成分，该类异染色质可以出现在染色体组的 23 个位置上。重复单元为 185 个碱基对，已被克隆到质粒 pBR322 中，并测定了其核苷酸序列。该 DNA 序列在结构异染色质中存在而在着丝粒、核仁及 B 染色体异染色质中不存在，与以前在玉米中描述的这些异染色质类别在细胞遗传学上的分化相平行。由于结构异染色质具有独特的细胞学特征，并且在减数分裂中表现出独特的新着丝粒活性，因此它与特定的重复 DNA 序列的关联可能反映了该序列在细胞周期中的功能作用。
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