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磷酸酶相互作用蛋白 NIPP1 调节组蛋白甲基转移酶 EZH2 在 Polycomb 靶标上的占有率。

The phosphatase interactor NIPP1 regulates the occupancy of the histone methyltransferase EZH2 at Polycomb targets.

机构信息

Laboratory of Biosignaling and Therapeutics, Department of Molecular Cell Biology, Faculty of Medicine, KULeuven, B-3000 Leuven, Belgium.

出版信息

Nucleic Acids Res. 2010 Nov;38(21):7500-12. doi: 10.1093/nar/gkq643. Epub 2010 Jul 29.

Abstract

Polycomb group (PcG) proteins are key regulators of stem-cell and cancer biology. They mainly act as repressors of differentiation and tumor-suppressor genes. One key silencing step involves the trimethylation of histone H3 on Lys27 (H3K27) by EZH2, a core component of the Polycomb Repressive Complex 2 (PRC2). The mechanism underlying the initial recruitment of mammalian PRC2 complexes is not well understood. Here, we show that NIPP1, a regulator of protein Ser/Thr phosphatase-1 (PP1), forms a complex with PP1 and PRC2 components on chromatin. The knockdown of NIPP1 or PP1 reduced the association of EZH2 with a subset of its target genes, whereas the overexpression of NIPP1 resulted in a retargeting of EZH2 from fully repressed to partially active PcG targets. However, the expression of a PP1-binding mutant of NIPP1 (NIPP1m) did not cause a redistribution of EZH2. Moreover, mapping of the chromatin binding sites with the DamID technique revealed that NIPP1 was associated with multiple PcG target genes, including the Homeobox A cluster, whereas NIPP1m showed a deficient binding at these loci. We propose that NIPP1 associates with a subset of PcG targets in a PP1-dependent manner and thereby contributes to the recruitment of the PRC2 complex.

摘要

多梳抑制复合物(PcG)蛋白是干细胞和癌症生物学的关键调节因子。它们主要作为分化和肿瘤抑制基因的抑制剂发挥作用。关键的沉默步骤之一涉及 EZH2 对组蛋白 H3 赖氨酸 27(H3K27)的三甲基化,EZH2 是多梳抑制复合物 2(PRC2)的核心组成部分。哺乳动物 PRC2 复合物初始募集的机制尚未得到很好的理解。在这里,我们表明,蛋白丝氨酸/苏氨酸磷酸酶-1(PP1)的调节剂 NIPP1 在染色质上与 PP1 和 PRC2 成分形成复合物。NIPP1 或 PP1 的敲低会减少 EZH2 与其部分靶基因的结合,而 NIPP1 的过表达会导致 EZH2 从完全沉默的 PcG 靶标重新靶向到部分激活的靶标。然而,NIPP1(NIPP1m)的 PP1 结合突变体的表达不会导致 EZH2 的重新分布。此外,利用 DamID 技术对染色质结合位点进行映射表明,NIPP1 与多个 PcG 靶基因相关,包括同源盒 A 簇,而 NIPP1m 在这些基因座上的结合能力较弱。我们提出,NIPP1 以依赖于 PP1 的方式与 PcG 靶标子集相关联,从而有助于 PRC2 复合物的募集。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/467d/2995064/bcf1e86b549f/gkq643f1.jpg

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