'Insulator bodies' are aggregates of proteins but not of insulators
'Insulator bodies' are aggregates of proteins but not of insulators
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DOI：
10.1038/embor.2008.32
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发表时间：
2008-05-01
期刊：
影响因子：
7.7
通讯作者：
Georgiev, Pavel
中科院分区：
文献类型：
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作者：
Golovnin, Anton;Melnikova, Larisa;Georgiev, Pavel
染色质绝缘体被认为限制增强剂和沉默剂的作用。果蝇中最著名的绝缘子需要蛋白质如毛翅抑制子（Suppressor of Hairy wing，Su（Hw））和mdg 4修饰子（Modifier of mdg 4，Mod（mdg 4））才能发挥功能。在免疫染色的细胞中，与绝缘子相关的蛋白质明显地以核斑点的形式共定位。有人断言，这些斑点是许多Su（Hw）-绝缘子DNA位点的“绝缘体”，这些绝缘体通过相关蛋白（包括Mod（mdg 4））保持在一起。正如我们在这里使用果蝇、幼虫和S2细胞所显示的，缺乏富Q结构域的突变Mod（mdg 4）蛋白支持Su（Hw）依赖性绝缘子的功能，并有效地结合到染色体上的正确绝缘子位点，但不形成或进入Su（Hw）标记的核斑点;相反，后者积累了另一个（C截短）Mod（mdg 4）突变体，该突变体不能与Su（Hw）或真正的绝缘子相互作用。因此，它不是功能性基因组绝缘体，而是聚集的蛋白质，使所谓的“绝缘体”。
Chromatin insulators are thought to restrict the action of enhancers and silencers. The best-known insulators in Drosophila require proteins such as Suppressor of Hairy wing (Su(Hw)) and Modifier of mdg4 (Mod(mdg4)) to be functional. The insulator-related proteins apparently colocalize as nuclear speckles in immunostained cells. It has been asserted that these speckles are 'insulator bodies' of many Su(Hw)-insulator DNA sites held together by associated proteins, including Mod(mdg4). As we show here using flies, larvae and S2 cells, a mutant Mod(mdg4) protein devoid of the Q-rich domain supports the function of Su(Hw)-dependent insulators and efficiently binds to correct insulator sites on the chromosome, but does not form or enter the Su(Hw)-marked nuclear speckles; conversely, the latter accumulate another (C-truncated) Mod(mdg4) mutant that cannot interact with Su(Hw) or with the genuine insulators. Hence, it is not the functional genomic insulators but rather aggregated proteins that make the so-called 'insulator bodies'.