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Trans-acting factors involved in heterochromatinization of the inactive X chromosome

参与失活 X 染色体异染色质化的反式作用因子

基本信息

批准号：
11672249
负责人：
YOSHIDA Ikuya
金额：
$ 2.3万
依托单位：
Research Center for Molecular Genetics, Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11672249/
关键词：
Human-mouse hybrid cells Microcell fusion X chromosome inactivation Heterochromatin Histone acetylation Sex chromatin body XIST RNA マウス不活性X染色体アセチル化 microcell fusion 細胞雑種ヒト

项目摘要

Mammalian X chromosome inactivation is a chromosome-wide phenomenon that leads to transcriptional silencing of one of the two X chromosomes in female somatic cells. The inactivated X chromosome shares striking properties, including asynchronous DNA replication, XIST RNA localization through the length of the X chromosome, sex chromatin body formation at nuclear periphery, and hypoacetylation of histone H4. Relationships among these properties and their relative importance, however, remain unknown. In the present study, we have tried to isolate trans-acting factors involved in heterochromatinization of the inactive human X chromosome.A human monochromosome hybrid, CF150 has one or more inactive human X chromosomes (Xi) as its only human element. In CF150 cells, the introduced Xi behaved abnormally ; (1) Xi did not form sex chromatin body at nucleus peripherally, (2) Xi was moderately acetylated as other mouse chromosomes, and (3) Xi was not coated with XIST RNA.The same Xi transferred f … More rom CF150 into HeLa cells behaved normally as the typical inactive X, suggesting full manifestation of these traits requires a certain human specific factor (s) that is depleted in CF150. A genetic complementation assay has been performed to determine which human chromosome bears the related genes, by microcell fusion.When Xi was introduced from CF150 into mouse embryonal carcinoma (EC) cell lines, the reversal of inactivation occurred, but XIST expressed persistently. Despite of its active chromatin state, the reactivated human X chromosome was coated with XIST RNA.Cell differentiation of these monochromosome EC hybrids leaded the dissociation of XIST RNA from the human X chromosome. When the same reactivated X chromosome was transferred from monochromosome EC hybrids into HeLa cells, the reactivated X chromosome was coated with XIST RNA.Together, these data suggest that two different factors (an undifferentiated and a somatic cell types, respectively) for Xist RNA localization exist in mouse cells. Less

哺乳动物X染色体失活是一种染色体范围内的现象，导致雌性体细胞中两条X染色体之一的转录沉默。失活的X染色体具有惊人的特性，包括异步DNA复制，XIST RNA在X染色体长度上的定位，核周围性染色质体的形成以及组蛋白H4的低乙酰化。然而，这些属性之间的关系及其相对重要性仍然未知。本研究试图分离出参与失活人类X染色体异染色质化的反式作用因子，CF150是一种人类单染色体杂种，具有一条或多条失活人类X染色体（Xi）作为其唯一的人类元件。在CF150细胞中，引入的Xi表现异常：（1）Xi在细胞核周围没有形成性染色质体，（2）Xi与其他小鼠染色体一样被中度乙酰化，（3）Xi没有被XIST RNA包被。 ...更多信息从CF150进入HeLa细胞后表现为典型的非活性X，表明这些特征的完全表现需要某种CF150耗尽的人类特异性因子。用微细胞融合技术，通过基因互补分析，确定了人染色体上的XIST基因，当XIST基因从CF 150导入小鼠胚胎癌细胞系（EC）后，失活逆转，但XIST基因持续表达。尽管染色质处于活性状态，但重新激活的人X染色体被XIST RNA包被，这些单染色体EC杂交体的细胞分化导致XIST RNA从人X染色体上解离。当相同的重新激活的X染色体从单染色体EC杂种转移到HeLa细胞中时，重新激活的X染色体被XIST RNA包被。总之，这些数据表明，两种不同的因素（未分化和体细胞类型，分别）Xist RNA定位在小鼠细胞中存在。少