Developmentally regulated histone modifications in Drosophila follicle cells:: initiation of gene amplification is associated with histone H3 and H4 hyperacetylation and H1 phosphorylation
Developmentally regulated histone modifications in Drosophila follicle cells:: initiation of gene amplification is associated with histone H3 and H4 hyperacetylation and H1 phosphorylation
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DOI：
10.1007/s00412-006-0092-2
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发表时间：
2007-04-01
期刊：
影响因子：
1.6
通讯作者：
Bosco, Giovanni
中科院分区：
文献类型：
--
作者：
Hartl, Tom;Boswell, Carl;Bosco, Giovanni
我们使用果蝇卵泡细胞中的基因扩增作为后生动物DNA复制的模型，以解决组蛋白修饰的变化是否与复制起源激活相关。我们观察到复制起始与不同的组蛋白修饰有关。组蛋白H4上的乙酰化赖氨酸K5、K8和K12和组蛋白H3上的K14在扩增起点的复制起始时特异性富集。引人注目的是，H4乙酰化在扩增起点持续存在，即使复制叉已从起点向外显著发展，这表明H4乙酰化与起点调控有关，而与复制叉的组蛋白沉积无关。具有严重扩增缺陷的起源识别复合体亚单位2 （orc2）突变体不会消除H4乙酰化，而dup/cdt1突变体延迟乙酰化灶的出现，rbf突变体导致时间持久性。这些数据表明核心组蛋白乙酰化与起源活性有关。此外，经历基因扩增的卵泡细胞表现出高水平的组蛋白H1磷酸化。H1磷酸化的模式提供了对扩增过程中细胞周期状态的深入了解，因为滤泡细胞中的H1激酶活性对高Cyclin E活性有反应，并且可以通过过度表达抑制Cyclin E的视网膜母细胞瘤同源物Rbf来消除。这些数据表明，当细胞处于s期晚期时，当基因组通常不允许复制时，扩增起源能够启动。
We have used gene amplification in Drosophila follicle cells as a model of metazoan DNA replication to address whether changes in histone modifications are associated with replication origin activation. We observe that replication initiation is associated with distinct histone modifications. Acetylated lysines K5, K8, and K12 on histone H4 and K14 on histone H3 are specifically enriched during replication initiation at the amplification origins. Strikingly, H4 acetylation persists at an amplification origin well after replication forks have progressed significantly outward from the origin, indicating that H4 acetylation is associated with origin regulation and not histone deposition at the replication forks. Origin recognition complex subunit 2 (orc2) mutants with severe amplification defects do not abolish H4 acetylation, whereas the dup/cdt1 mutant delays the appearance of acetylation foci, and mutants in rbf result in temporal persistence. These data indicate that core histone acetylation is associated with origin activity. Furthermore, follicle cells undergoing gene amplification exhibit high levels of histone H1 phosphorylation. The patterns of H1 phosphorylation provide insights into cell cycle states during amplification, as H1 kinase activity in follicle cells is responsive to high Cyclin E activity, and it can be abolished by overexpressing the retinoblastoma homolog, Rbf, that represses Cyclin E. These data suggest that amplification origins are able to initiate when the cells are in a late S-phase, when the genome is normally not licensed for replication.