Familial cases of point mutations in the XIST promoter reveal a correlation between CTCF binding and pre-emptive choices of X chromosome inactivation
Familial cases of point mutations in the XIST promoter reveal a correlation between CTCF binding and pre-emptive choices of X chromosome inactivation
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DOI：
10.1093/hmg/ddi089
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发表时间：
2005-04-01
影响因子：
3.5
通讯作者：
Lobanenkov, VV
中科院分区：
文献类型：
--
作者：
Pugacheva, EM;Tiwari, VK;Lobanenkov, VV
决定雌性哺乳动物体细胞中未来失活X染色体的选择机制涉及XIST基因的调节表达。XIST启动子中的家族性C（-43）G突变导致X染色体失活（XCI）向杂合女性的失活X染色体倾斜，而主要在活性X染色体中发现的C（-43）A突变导致相反的倾斜模式。这两种突变都表明存在一种可能导致这种扭曲模式的因素。在这里，我们确定这个因素CTCF，一个保守的蛋白质与11锌指（ZF）结构域，可以介导多种序列特异性和DNA结合的CTCF分子之间的相互作用。我们表明，小鼠和人Xist/XIST启动子含有一个同源的CTCF结合序列与匹配的dG-接触，在人XIST中包括-43位置内的DNA酶I足迹的CTCF。虽然C（-43）A突变消除CTCF结合，但C（-43）G突变通过改变识别突变位点的改变的dG接触所需的ZF使用模式而导致CTCF结合效率的显著增加。因此，两个-43C突变的偏斜效应与它们对CTCF结合的效应相关。最后，CTCF仅在雌性人类和小鼠细胞中与XIST/Xist启动子相互作用。这反映了与活性Xist等位基因的启动子的优先相互作用的解释在小鼠胎儿胎盘中得到证实。这些观察结果与X染色体失活的选择反映了冲击CTCF-XIST启动子复合物的高阶染色质构象的稳定化的可能性一致。
The choice mechanisms that determine the future inactive X chromosome in somatic cells of female mammals involve the regulated expression of the XIST gene. A familial C(-43)G mutation in the XIST promoter results in skewing of X chromosome inactivation (XCI) towards the inactive X chromosome of heterozygous females, whereas a C(-43)A mutation found primarily in the active X chromosome results in the opposite skewing pattern. Both mutations point to the existence of a factor that might be responsible for the skewed patterns. Here we identify this factor as CTCF, a conserved protein with a 11 Zn-finger (ZF) domain that can mediate multiple sequence-specificity and interactions between DNA-bound CTCF molecules. We show that mouse and human Xist/XIST promoters contain one homologous CTCF-binding sequence with the matching dG-contacts, which in the human XIST include the -43 position within the DNase I footprint of CTCF. While the C(-43)A mutation abrogates CTCF binding, the C(-43)G mutation results in a dramatic increase in CTCF-binding efficiency by altering ZF-usage mode required for recognition of the altered dG-contacts of the mutant site. Thus, the skewing effect of the two -43C mutations correlates with their effects on CTCF binding. Finally, CTCF interacts with the XIST/Xist promoter only in female human and mouse cells. The interpretation that this reflected a preferential interaction with the promoter of the active Xist allele was confirmed in mouse fetal placenta. These observations are in keeping with the possibility that the choice of X chromosome inactivation reflects stabilization of a higher order chromatin conformation impinging on the CTCF-XIST promoter complex.