Formation of facultative heterochromatin in the absence of HP1
Formation of facultative heterochromatin in the absence of HP1
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DOI：
10.1093/emboj/cdg520
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发表时间：
2003-10-15
期刊：
影响因子：
11.4
通讯作者：
Bickmore, WA
中科院分区：
文献类型：
--
作者：
Gilbert, N;Boyle, S;Bickmore, WA
兼性异染色质是调控基因表达的表观遗传机制的细胞学表现。组成型异染色质以独特的组蛋白H3甲基化和HP1蛋白的存在为特征，但兼性异染色质的染色质修饰尚不清楚。我们研究了有核红细胞兼性异染色质中的组蛋白修饰和HP1，并表明小鼠和鸡红细胞具有不同的异染色质形成机制。小鼠胚胎红细胞具有丰富的HP1， K9位点H3三甲基化增加，K27位点H3三甲基化缺失。相反，我们发现HP1蛋白在鸡红细胞分化过程中丢失，并且K9和K27处的H3三甲基化都减少。这与变异连接蛋白H5的出现一致。爪蟾和斑马鱼的红细胞中也不存在HP1s。我们的数据表明，在同一细胞系中，脊椎动物形成兼性异染色质的机制不同。据我们所知，这是第一次报道缺乏hp1的细胞类型，并且在组蛋白修饰水平上有明显的变化。
Facultative heterochromatin is a cytological manifestation of epigenetic mechanisms that regulate gene expression. Constitutive heterochromatin is marked by distinctive histone H3 methylation and the presence of HP1 proteins, but the chromatin modifications of facultative heterochromatin are less clear. We have examined histone modifications and HP1 in the facultative heterochromatin of nucleated erythrocytes and show that mouse and chicken erythrocytes have different mechanisms of heterochromatin formation. Mouse embryonic erythrocytes have abundant HP1, increased tri-methylation of H3 at K9 and loss of H3 tri-methylation at K27. In contrast, we show that HP1 proteins are lost during the differentiation of chicken erythrocytes, and that H3 tri-methylation at both K9 and K27 is reduced. This coincides with the appearance of the variant linker histone H5. HP1s are also absent from erythrocytes of Xenopus and zebrafish. Our data show that in the same cell lineage there are different mechanisms for forming facultative heterochromatin in vertebrates. To our knowledge, this is the first report of cell types that lack HP1s and that have gross changes in the levels of histone modifications.