Rutgers University, Department of Molecular Biology and Biochemistry, Piscataway, NJ 08854, USA.
Mol Cell Biol. 2011 Feb;31(4):616-25. doi: 10.1128/MCB.00849-10. Epub 2010 Dec 6.
The genomic binding sites of Polycomb group (PcG) complexes have been found to cluster, forming Polycomb "bodies" or foci in mammalian or fly nuclei. These associations are thought to be driven by interactions between PcG complexes and result in enhanced repression. Here, we show that a Polycomb response element (PRE) with strong PcG binding and repressive activity cannot mediate trans interactions. In the case of the two best-studied interacting PcG targets in Drosophila, the Mcp and the Fab-7 regulatory elements, we find that these associations are not dependent on or caused by the Polycomb response elements they contain. Using functional assays and physical colocalization by in vivo fluorescence imaging or chromosome conformation capture (3C) methods, we show that the interactions between remote copies of Mcp or Fab-7 elements are dependent on the insulator activities present in these elements and not on their PREs. We conclude that insulator binding proteins rather than PcG complexes are likely to be the major determinants of the long-range higher-order organization of PcG targets in the nucleus.
多梳抑制复合物 (PcG) 复合体的基因组结合位点已被发现聚集在一起，在哺乳动物或果蝇核中形成多梳“体”或焦点。这些关联被认为是由 PcG 复合物之间的相互作用驱动的，并导致增强的抑制。在这里，我们表明具有强 PcG 结合和抑制活性的多梳反应元件 (PRE) 不能介导转录相互作用。在果蝇中研究最深入的两个相互作用的 PcG 靶标 Mcp 和 Fab-7 调控元件的情况下，我们发现这些关联不是由它们包含的多梳反应元件引起的。通过功能测定和体内荧光成像或染色体构象捕获 (3C) 方法的物理共定位，我们表明 Mcp 或 Fab-7 元件的远程拷贝之间的相互作用依赖于这些元件中的绝缘子活性，而不是它们的 PRE。我们得出的结论是，绝缘子结合蛋白而不是 PcG 复合物很可能是 PcG 靶标在核中长距离高级组织的主要决定因素。
