Transcriptional enhancers act in cis to suppress position-effect variegation.
Transcriptional enhancers act in cis to suppress position-effect variegation.
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转录增强子以顺式作用抑制位置效应杂色。
DOI：
10.1101/gad.10.2.185
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发表时间：
1996
影响因子：
10.5
通讯作者：
Martin,DI
中科院分区：
文献类型：
--
作者：
Walters,MC;Magis,W;Fiering,S;Eidemiller,J;Scalzo,D;Groudine,M;Martin,DI
我们通过改变增强子对稳定整合的报告基因表达的作用，研究了增强子对基因表达影响的基础。我们使用了两种不同的实验方法：重组酶介导的增强子的缺失和由下游金属响应元件（MRE）组成的另一个增强子的活性的调制。flp重组酶用于从K562红白血病细胞中9个独立整合位点处的β-geo下游位点缺失5 'HS 2珠蛋白增强子。在任何情况下，5 'HS 2的缺失对表达水平都没有显著影响;然而，缺失确实显著增加了β-geo表达沉默的速率。金属硫蛋白增强子的锌刺激对报告基因表达水平没有影响，但减慢了沉默的速率。这两种情况下的沉默都是高度位点依赖性的，类似于位置效应杂色（PEV）。这些结果强烈支持增强子作用的二元模式，因为在两种情况下，增强子维持报告基因表达，而对表达水平没有强烈影响。总之，这些发现表明，转录激活因子与抑制性染色质结构有直接的相互作用，这是独立的对转录速率的影响。我们建议，顺式作用的转录控制元件可能主要通过这种机制。
We have examined the basis of enhancer effects on gene expression by altering the action of enhancers on expression of a stably integrated reporter gene. We used two distinct experimental approaches: recombinase-mediated deletion of an enhancer and modulation of the activity of another enhancer composed of downstream metal response elements (MREs). The flp recombinase was used to delete the 5'HS2 globin enhancer from a site downstream of beta-geo at nine separate integration sites in K562 erythroleukemia cells. In no case does deletion of 5'HS2 have a significant effect on the level of expression; however, the deletion does increase dramatically the rate at which expression of beta-geo is silenced. Zinc stimulation of a metallothionein enhancer has no effect on the level of reporter expression, but slows the rate of silencing. Silencing in both cases is highly site dependent, and resembles position-effect variegation (PEV). These results strongly support a binary mode of enhancer action, as in both cases the enhancer maintains reporter expression without a strong effect on the level of expression. Taken together, these findings suggest that transcriptional activators have a direct interaction with repressive chromatin structures, which is independent of an effect on the rate of transcription. We propose that cis-acting transcriptional control elements may act primarily through this mechanism.