Gfi1b alters histone methylation at target gene promoters and sites of γ-satellite containing heterochromatin
Gfi1b alters histone methylation at target gene promoters and sites of γ-satellite containing heterochromatin
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DOI：
10.1038/sj.emboj.7601124
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发表时间：
2006-06-07
期刊：
影响因子：
11.4
通讯作者：
Moeroey, Tarik
中科院分区：
文献类型：
--
作者：
Vassen, Lothar;Fiolka, Katharina;Moeroey, Tarik
Gfi 1b是一种37 kDa的核蛋白，具有6个C2 H2锌指结构域，可在与特定靶基因启动子结合后沉默转录。在这里，我们通过使用染色质免疫沉淀和克隆协议，Gfi 1b也结合到C-卫星序列，主要发生在臂间异染色质。免疫荧光原位杂交实验表明，Gfi 1b定位于由DAPI染色鉴定的臂间异染色质的病灶。Gfi 1b水平的升高与组蛋白H3赖氨酸9二甲基化的增加相关，这些二甲基化发生在邻近γ-卫星序列的位点处，也发生在Gfi 1b靶基因启动子处。然而，在Gfi 1b缺陷细胞中，观察到组蛋白H3赖氨酸9三甲基化的减少和异染色质结构的丧失。引人注目的是，我们发现Gfi 1b与SUV 39 H1和G9 A组蛋白甲基转移酶结合，这在异染色质和常染色质位点提供了组蛋白甲基化与Gfi 1b之间的直接联系。我们建议，Gfi 1b功能异染色质的形成和沉默常染色质转录招募组蛋白甲基转移酶的C-卫星序列或特定的靶基因启动子。
Gfi1b is a 37 kDa nuclear protein with six C2H2 zinc-finger domains that can silence transcription upon binding to specific target gene promoters. Here we show by using a chromatin immunoprecipitation and cloning protocol that Gfi1b also binds to c-satellite sequences that mainly occur in pericentric heterochromatin. Immuno-FISH experiments demonstrated that Gfi1b is localized at foci of pericentric heterochromatin identified by DAPI staining. Elevated levels of Gfi1b correlated with increased histone H3 lysine 9 dimethylation at sites neighboring gamma-satellite sequences but also at Gfi1b target gene promoters. In Gfi1b-deficient cells, however, a decrease of histone H3 lysine 9 trimethylation and a loss of heterochromatic structures was observed. Strikingly, we found that Gfi1b binds to both SUV39H1 and G9A histone methyl transferases, which provides a direct link between histone methylation and Gfi1b at heterochromatic and euchromatic sites. We propose that Gfi1b functions in heterochromatin formation and silencing of euchromatic transcription by recruiting histone methyl transferases to either c-satellite sequences or specific target gene promoters.