Mutational analysis of the chicken beta-globin enhancer reveals two positive-acting domains.
Mutational analysis of the chicken beta-globin enhancer reveals two positive-acting domains.
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鸡 β-珠蛋白增强子的突变分析揭示了两个积极作用的结构域。
DOI：
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发表时间：
1988
影响因子：
11.1
通讯作者：
G. Felsenfeld
中科院分区：
文献类型：
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作者：
Marc L. Reitman;G. Felsenfeld
我们报告了鸡β-珠蛋白增强子的突变分析，使用初级胚胎红细胞中的瞬时表达。一系列的27个扫描突变体的不同，只有连续的4个碱基取代进行了测试。以前的实验，使用保护DNA酶I消化，证明了四个区域的增强子结合因子。在四个区域中的两个区域（表示为I和III）中的突变对增强子活性没有影响。其他两个区域（II和IV）介导所有的正作用活性。区域II似乎由两个亚区域组成，其中任何一个亚区域的突变都会导致与两者突变相同的活性丧失。与区域II类似，区域IV的任一半的突变导致增强子活性降低。然而，与区域II相反，区域IV的两个半部分的突变导致增强子活性的损失比任一单个突变更多。这些数据表明，在区域II的半网站必须相互作用，以引起增强，而在区域IV的半网站独立行事。区域II或IV的三重拷贝能够增强到与亲本增强子相似的程度，但是区域II或IV的单拷贝仅微弱地增强。因此，如通过在胚胎红细胞中的瞬时表达所测量的，β-珠蛋白增强子可能涉及在两个位点起作用的少至三个DNA结合蛋白的作用。
We report a mutational analysis of the chicken beta-globin enhancer, using transient expression in primary embryonic erythrocytes. A series of 27 scanning mutants differing only by consecutive 4-base substitutions was tested. Previous experiments, using protection from DNase I digestion, demonstrated four regions in the enhancer that bind factors. Mutations in two of the four regions (denoted I and III) have no effect on enhancer activity. The other two regions (II and IV) mediate all of the positive-acting activity. Region II appears to consist of two subregions, mutation in either of which leads to the same loss in activity as mutation of both. Like region II, mutation of either half of region IV results in reduced enhancer activity. However, in contrast to region II, mutation of both halves of region IV results in more loss of enhancer activity than either single mutation. These data suggest that the half-sites in region II must interact in order to cause enhancement, whereas the half-sites in region IV act independently. Triplications of regions II or IV are able to enhance to a similar degree as the parental enhancer, but single copies of regions II or IV enhance only weakly. Thus, as measured by transient expression in embryonic erythrocytes, the beta-globin enhancer may involve the action of as few as three DNA-binding proteins acting at two sites.