A region of euchromatin coincides with an extensive tandem repeat on the mouse (Mus musculus) inactive X chromosome
A region of euchromatin coincides with an extensive tandem repeat on the mouse (Mus musculus) inactive X chromosome
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DOI：
10.1007/s10577-014-9424-x
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发表时间：
2014-09-01
影响因子：
2.6
通讯作者：
Chadwick, Brian P.
中科院分区：
文献类型：
--
作者：
Darrow, Emily M.;Seberg, Andrew P.;Chadwick, Brian P.
人类失活的X染色体（Xi）基本上不存在常染色质特征，除了在中期可以检测到几个大串联重复序列的常染色质带。尽管这些串联重复序列相隔百万碱基，但它们经常产生非活性的x特异性相互作用。小鼠同源物已经报道了至少一个串联重复序列，但小鼠Xi是否也具有不同的常染色质带仍然未知。我们通过检测组蛋白H3在赖氨酸4处二甲基化的模式来检测小鼠Xi是否存在常染色质带，并检测到两个主要信号。第一条带位于条带XF5的亚端粒区域，可能对应于假常染色体区域。第二个条带定位于XE3，与一个广泛的复杂重复序列相吻合，该重复序列由一个大的串联重复和倒置重复片段以及几个大的短的富含核元素（SINE）的串联重复组成。荧光原位杂交显示，与重复区域同源的序列沿Y染色体的长度分散。免疫荧光分析中期染色体赖氨酸9处三甲基化的组蛋白H3表明，重复区域对应于雄性X和雌性活性X染色体上的一个组成型异染色质带，而常染色质信号似乎是女性特有的。这些数据表明，在XE3观察到的常染色质带是小鼠Xi所特有的，与位于人类X染色体上的几个大串联重复序列的染色质排列相当。
Euchromatic features are largely absent from the human inactive X chromosome (Xi), with the exception of several large tandem repeats that can be detected as euchromatin bands at metaphase. Despite residing megabases apart, these tandem repeats make frequent inactive X-specific interactions. The mouse homologue has been reported for at least one of the tandem repeats, but whether the mouse Xi is also characterized by distinct bands of euchromatin remains unknown. We examined the mouse Xi for the presence of euchromatin bands by examining the pattern of histone H3 dimethylated at lysine 4 and detected two major signals. The first band resides in the subtelomeric region of band XF5 and may correspond to the pseudoautosomal region. The second band localizes to XE3 and coincides with an extensive complex repeat composed of a large tandem and inverted repeat segment as well as several large short interspersed nuclear element (SINE)-rich tandem repeats. Fluorescence in situ hybridization reveals that sequences with homology to the repeat region are scattered along the length of the Y chromosome. Immunofluorescence analysis of histone H3 trimethylated at lysine 9 on metaphase chromosomes indicates that the repeat region corresponds to a band of constitutive heterochromatin on the male X and female active X chromosomes, whereas the euchromatin signal appears to be female specific. These data suggest that the band of euchromatin observed at XE3 is unique to the mouse Xi, comparable to the chromatin arrangement of several large tandem repeats located on the human X chromosome.