Nussinov R, Shapiro B, Lipkin L E, Maizel J V
Biochim Biophys Acta. 1984 Dec 14;783(3):246-57. doi: 10.1016/0167-4781(84)90035-6.
Several experiments have shown that some enhancers can be exchanged between different genomes. The transferred enhancers were functional (cf. Levinson, B., Khoury, G., Vande Woude, G. and Gruss, P. (1982) Nature 295, 568-572). This argues that these exchanged fragments are recognized as enhancers and possess some common characteristics which other sequences lack. Extensive comparisons of enhancers yielded only very limited nucleotide sequence homology, which appears to be insufficient for enhancer recognition. We suggest that the enhancers located and sequenced to date have recurring, periodic homologous twist-angle (tg) patterns. This helical periodicity and the symmetric nature of the repeating twist-angle features present a recurring spatial geometry. It also offers a possible explanation of the fact that inverted enhancers are still functional. Regions of large twist, roll or main-chain torsion angle delta deviations from regular B-DNA may facilitate enhancer recognition especially when distant from promoter elements. Tissue specificity may be encoded in additional sequence or structural features.
多项实验表明，一些增强子可以在不同基因组之间交换。转移的增强子具有功能（参见Levinson, B., Khoury, G., Vande Woude, G. 和Gruss, P. (1982) 《自然》295, 568 - 572）。这表明这些交换的片段被识别为增强子，并具有一些其他序列所缺乏的共同特征。对增强子进行广泛比较仅产生了非常有限的核苷酸序列同源性，这似乎不足以用于增强子识别。我们认为，迄今为止定位和测序的增强子具有重复的、周期性的同源扭曲角（tg）模式。这种螺旋周期性以及重复扭曲角特征的对称性质呈现出一种重复的空间几何形状。这也为倒置增强子仍然具有功能这一事实提供了一种可能的解释。与规则B - DNA相比，大扭曲、滚动或主链扭转角δ偏差较大的区域可能有助于增强子识别，尤其是当它们远离启动子元件时。组织特异性可能编码在额外的序列或结构特征中。
