A DNA insulator prevents repression of a targeted X-linked transgene but not its random or imprinted X inactivation
A DNA insulator prevents repression of a targeted X-linked transgene but not its random or imprinted X inactivation
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DOI：
10.1073/pnas.0603754103
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发表时间：
2006-06-27
影响因子：
11.1
通讯作者：
Smithies, Oliver
中科院分区：
文献类型：
--
作者：
Ciavatta, Dominic;Kalantry, Sundeep;Smithies, Oliver
不活跃的X染色体上的一些基因逃脱了沉默。一种可能的逃逸机制是X失活过程中的异染色化可以被边界元素阻止。DNA绝缘体是阻断的候选对象，因为它们保护基因免受染色体环境的影响。为了测试DNA绝缘子是否可以作为X染色体上的边界，我们在X连锁的小鼠HPRT基因座中插入了GFP转基因，侧翼带有来自鸡β-珠蛋白基因座的原型脊椎动物绝缘子的零个、一个或两个副本，即鸡肉超敏部位4，它包含CCCTC结合因子结合位点。在活跃的X染色体上，绝缘体以拷贝数依赖的方式阻止了转基因的抑制，转基因开始于早期发育并在成人中持续存在。转基因的CpG甲基化与表达呈负相关，但活性X染色体上的绝缘子没有甲基化。在失活的X染色体上，绝缘子没有阻断转基因的随机失活或印迹X失活，绝缘子和转基因几乎都完全甲基化。因此，鸡超敏感部位4的DNA绝缘体足以保护X连锁基因在发育过程中免受抑制，但不能防止X失活。
Some genes on the inactive X chromosome escape silencing. One possible escape mechanism is that heterochromatization during X inactivation can be blocked by boundary elements. DNA insulators are candidates for blocking because they shield genes from influences of their chromosomal environment. To test whether DNA insulators can act as boundaries on the X chromosome, we inserted into the mouse X-linked Hprt locus a GFP transgene flanked with zero, one, or two copies of a prototypic vertebrate insulator from the chicken beta-globin locus, chicken hypersensitive site 4, which contains CCCTC binding factor binding sites. On the active X chromosome the insulators blocked repression of the transgene, which commences during early development and persists in adults, in a copy number-dependent manner. CpG methylation of the transgene correlated inversely with expression, but the insulators on the active X chromosome were not methylated. On the inactive X chromosome, insulators did not block random or imprinted X inactivation of the transgene, and both the insulator and transgene were almost completely methylated. Thus, the chicken hypersensitive site 4 DNA insulator is sufficient to protect an X-linked gene from repression during development but not from X inactivation.