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首页> 外文期刊>Molecular and Cellular Biology >The activity of the scs and scs' insulator elements is not dependent on chromosomal context.
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The activity of the scs and scs' insulator elements is not dependent on chromosomal context.

机译：scs和scs的绝缘子元素的活动不依赖于染色体上下文。

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Sequence elements that protect a reporter gene from chromosomal position effects or that block enhancer-activated transcription are called insulators. Using a plasmid-based microinjection assay with Xenopus laevis oocytes, we show that the heterologous Drosophila melanogaster scs and scs' insulator elements do not require chromosomal context to block enhancer-activated transcription. A single insulator element partially blocks enhancer-activated transcription, indicating that each element operates independently rather than as part of a pair. Deletion analysis of the 1.8-kb scs element identified a 220-bp fragment from one of the DNase I-hypersensitive regions that has full blocking activity in the oocyte assay. This fragment corresponds to the critical region of the scs mapped in previous studies with Drosophila. A time course of transcription shows that the scs blocks enhancer-activated transcription as early as transcription can be detected, about 30 min after injection. Complete assembly of the DNA template into nucleosomes requires 4 h. The scs and scs' sequences do not block site-specific recombination by FLP recombinase, implying that insulators do not operate by a general mechanism that physically sequesters the DNA. These data are most consistent with a model for insulator action in which direct interaction between the insulator and either the enhancer or promoter confers directionality to enhancer-activated transcription.
机译：保护报告基因不受染色体位置影响或阻断增强子激活的转录的序列元件被称为绝缘子。使用非洲爪蟾卵母细胞的基于质粒的显微注射测定，我们显示异源果蝇果蝇sc和scs的绝缘子元素不需要染色体的上下文来阻止增强子激活的转录。单个绝缘体元件部分阻断增强子激活的转录，表明每个元件独立运行，而不是作为一对的一部分运行。对1.8-kb scs元件的缺失分析从DNase I超敏感区之一中鉴定出一个220-bp的片段，该片段在卵母细胞测定中具有完全的阻断活性。该片段对应于果蝇先前研究中定位的scs的关键区域。转录的时间过程显示，注射后约30分钟，scs可以在最早检测到转录时阻断增强子激活的转录。将DNA模板完全组装成核小体需要4小时。 scs和scs的序列不会通过FLP重组酶阻断位点特异性重组，这意味着绝缘子不会通过物理隔离DNA的通用机制起作用。这些数据与绝缘子作用模型最一致，在该模型中，绝缘子与增强子或启动子之间的直接相互作用将方向性赋予增强子激活的转录。

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