Heterochromatin biology

异染色质生物学

• 批准号: 8939560
• 负责人: Gary Felsenfeld
• 金额: $ 35.11万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8939560
• 关键词: Acetylation; Binding; Biochemical; Biology; Cell Line; Cell physiology; Chickens; Chromatin Structure; Coupled; Erythroid Cells; Fission Yeast; Genes; Genetic Transcription; Genomics; Heterochromatin; Histone Acetylation; Histone Deacetylase Inhibitor; Histone H3; Histone H4; Homeostasis; Human; K-562; Lysine; Maintenance; Measures; Molecular Conformation; Pattern; Property; Publishing; Recombinant DNA; Regulation; Ribosomal RNA; Role; Small Interfering RNA; Structure; Vertebrates; Yeasts; beta Globin; histone modification; human DICER1 protein; rRNA Genes; vertebrate genome

We are studying the mechanisms that maintain constitutive heterochromatic regions in a condensed form. For this purpose we originally used a well characterized 16 kb heterochromatin segment located upstream of the chicken beta globin locus. In other published studies we have measured the hydrodynamic properties of this fragment, which is typical of a large proportion of vertebrate genomes, and which has the potential if unregulated to silence adjacent genes in a manner deleterious to cellular function. We found that maintenance of the condensed structure is coupled to low level transcription in the region, and that elevation of levels of histone acetylation by use of histone deacetylase inhibitors (TSA) markedly increases transcription. We asked whether Dicer/Argonaute dependent mechanisms could be involved in formation of this heterochromatic region. We found that depletion of Dicer by siRNA resulted in opening of the condensed chromatin structure much as what was observed following TSA treatment. Furthermore, Ago2 is bound to this region in a Dicer-dependent manner. We have now investigated the binding of Ago2 to the ribosomal gene repeats in the human erythroid cell line, K562. Loss of Ago2 binding to the rRNA genes causes an increase in histone H4 acetylation and a decrease in histone H3 lysine 9-dimethylation. This change in histone modification pattern is accompanied by loss of SUV39H1 recruitment and an increase in rRNA synthesis rates. These results demonstrate an important role for Ago2 in regulation of silent rDNA chromatin structure, which is a critical focal point for overall cellular homeostasis.

我们正在研究以浓缩形式维持本构异色区域的机制。为此，我们最初使用了位于鸡 β 珠蛋白基因座上游的已明确表征的 16 kb 异染色质片段。在其他发表的研究中，我们测量了该片段的流体动力学特性，该片段是大部分脊椎动物基因组的典型特征，如果不加调控，它有可能以对细胞功能有害的方式沉默相邻基因。我们发现，浓缩结构的维持与该区域的低水平转录相关，并且通过使用组蛋白脱乙酰酶抑制剂（TSA）提高组蛋白乙酰化水平会显着增加转录。我们询问 Dicer/Argonaute 依赖性机制是否可能参与该异染色质区域的形成。我们发现，通过 siRNA 去除 Dicer 会导致浓缩染色质结构打开，这与 TSA 处理后观察到的情况非常相似。此外，Ago2 以 Dicer 依赖性方式与该区域结合。 我们现在已经研究了 Ago2 与人红系细胞系 K562 中核糖体基因重复的结合。 Ago2 与 rRNA 基因结合的丧失会导致组蛋白 H4 乙酰化增加和组蛋白 H3 赖氨酸 9-二甲基化减少。 组蛋白修饰模式的这种变化伴随着 SUV39H1 募集的丧失和 rRNA 合成率的增加。 这些结果证明了 Ago2 在调节沉默 rDNA 染色质结构中的重要作用，这是整体细胞稳态的关键焦点。