Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
J Cell Biol. 2013 Dec 9;203(5):767-83. doi: 10.1083/jcb.201305027. Epub 2013 Dec 2.
Increasing evidence points to nuclear compartmentalization as a contributing mechanism for gene regulation, yet mechanisms for compartmentalization remain unclear. In this paper, we use autonomous targeting of bacterial artificial chromosome (BAC) transgenes to reveal cis requirements for peripheral targeting. Three peripheral targeting regions (PTRs) within an HBB BAC bias a competition between pericentric versus peripheral heterochromatin targeting toward the nuclear periphery, which correlates with increased H3K9me3 across the β-globin gene cluster and locus control region. Targeting to both heterochromatin compartments is dependent on Suv39H-mediated H3K9me3 methylation. In different chromosomal contexts, PTRs confer no targeting, targeting to pericentric heterochromatin, or targeting to the periphery. A combination of fluorescent in situ hybridization, BAC transgenesis, and knockdown experiments reveals that peripheral tethering of the endogenous HBB locus depends both on Suv39H-mediated H3K9me3 methylation over hundreds of kilobases surrounding HBB and on G9a-mediated H3K9me2 methylation over flanking sequences in an adjacent lamin-associated domain. Our results demonstrate that multiple cis-elements regulate the overall balance of specific epigenetic marks and peripheral gene targeting.
越来越多的证据表明核区室化是基因调控的一个促成机制,但区室化的机制仍不清楚。在本文中,我们使用细菌人工染色体 (BAC) 转基因的自主靶向来揭示周边靶向的顺式要求。HBB BAC 内的三个周边靶向区域 (PTR) 偏向于中心体与周边异染色质之间的竞争,靶向核周,这与整个β-珠蛋白基因簇和基因座控制区的 H3K9me3 增加有关。针对两个异染色质区室的靶向都依赖于 Suv39H 介导的 H3K9me3 甲基化。在不同的染色体环境中,PTR 不赋予靶向、靶向中心体异染色质或靶向外围。荧光原位杂交、BAC 转基因和敲低实验的组合表明,内源性 HBB 基因座的外周固定既依赖于数百个碱基对周围的 HBB 上的 Suv39H 介导的 H3K9me3 甲基化,也依赖于相邻层粘连蛋白相关结构域中的侧翼序列上的 G9a 介导的 H3K9me2 甲基化。我们的结果表明,多个顺式元件调节特定表观遗传标记和外周基因靶向的整体平衡。