Larsen A, Weintraub H
Cell. 1982 Jun;29(2):609-22. doi: 10.1016/0092-8674(82)90177-5.
The single-stranded activity of S1-nuclease cleaves globin chromatin in red cell nuclei in specific regions. The cleavages are observed only in tissues in which the globin genes are active, and they "switch" to reflect the switching pattern of globin-gene expression in embryonic and adult red cells. The positions of the S1 cleavages in the beta- and alpha-globin chromatin correspond to the general region of known DNAase I-hypersensitive sites, but can be distinguished in detail. When DNA segments containing these regions are subcloned into pBR322 and the supercoiled molecules are treated with S1, similar sites are cleaved in the purified supercoiled (but not linear) recombinant plasmid DNA. However, the dominant S1 cutting sites are shifted in the plasmid vis-a-vis the chromatin. We believe that some aspect of DNA sequence is translated into an altered DNA structure in chromatin and that it is this altered structure that is recognized by s1 nuclease and possibly by certain chromosomal proteins. Several physical properties reflected in the S1 digestion of supercoiled plasmids suggest a mechanism for generating differences in daughter cells during development.
S1核酸酶的单链活性可在红细胞核内的特定区域切割珠蛋白染色质。这种切割仅在珠蛋白基因活跃的组织中观察到，并且它们会“切换”以反映胚胎和成年红细胞中珠蛋白基因表达的切换模式。β-和α-珠蛋白染色质中S1切割的位置与已知的DNA酶I高敏位点的大致区域相对应，但在细节上可以区分。当将包含这些区域的DNA片段亚克隆到pBR322中，并用S1处理超螺旋分子时，纯化的超螺旋（而非线性）重组质粒DNA中类似的位点会被切割。然而，与染色质相比，质粒中的主要S1切割位点发生了偏移。我们认为，DNA序列的某些方面被转化为染色质中改变的DNA结构，正是这种改变的结构被S1核酸酶以及可能被某些染色体蛋白所识别。超螺旋质粒的S1消化所反映的几种物理特性提示了一种在发育过程中产生子代细胞差异的机制。
