Institute of Pathology, University of Bonn, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany.
J Biol Chem. 2012 Sep 7;287(37):30984-92. doi: 10.1074/jbc.M112.341040. Epub 2012 Jul 23.
Fbxl10 (Jhdm1b/Kdm2b) is a conserved and ubiquitously expressed member of the JHDM (JmjC domain-containing histone demethylase) family. Fbxl10 was implicated in the demethylation of H3K4me3 or H3K36me2 thereby removing active chromatin marks and inhibiting gene transcription. Apart from the JmjC domain, Fbxl10 consists of a CxxC domain, a PHD domain, and an Fbox domain. By purifying the JmjC and the PHD domain of Fbxl10 and using different approaches we were able to characterize the properties of these domains in vitro. Our results suggest that Fbxl10 is rather a H3K4me3 than a H3K36me2 histone demethylase. The PHD domain exerts a dual function in binding H3K4me3 and H3K36me2 and exhibiting E3 ubiquitin ligase activity. We generated mouse embryonic fibroblasts stably overexpressing Fbxl10. These cells reveal an increase in cell size but no changes in proliferation, mitosis, or apoptosis. Using a microarray approach we were able to identify potentially new target genes for Fbxl10 including chemokines, the noncoding RNA Xist, and proteins involved in metabolic processes. Additionally, we found that Fbxl10 is recruited to the promoters of Ccl7, Xist, Crabp2, and RipK3. Promoter occupancy by Fbxl10 was accompanied by reduced levels of H3K4me3 but unchanged levels of H3K36me2. Furthermore, knockdown of Fbxl10 using small interfering RNA approaches showed inverse regulation of Fbxl10 target genes. In summary, our data reveal a regulatory role of Fbxl10 in cell morphology, chemokine expression, and the metabolic control of fibroblasts.
Fbxl10（Jhdm1b/Kdm2b）是 JHDM（含 JmjC 结构域的组蛋白去甲基酶）家族中保守且广泛表达的成员。Fbxl10 参与 H3K4me3 或 H3K36me2 的去甲基化，从而去除活性染色质标记并抑制基因转录。除了 JmjC 结构域外，Fbxl10 还包含一个 CxxC 结构域、一个 PHD 结构域和一个 Fbox 结构域。通过纯化 Fbxl10 的 JmjC 和 PHD 结构域，并采用不同的方法，我们能够在体外表征这些结构域的性质。我们的结果表明，Fbxl10 更像是一种 H3K4me3 去甲基酶，而不是 H3K36me2 去甲基酶。PHD 结构域在结合 H3K4me3 和 H3K36me2 并发挥 E3 泛素连接酶活性方面具有双重功能。我们生成了稳定过表达 Fbxl10 的小鼠胚胎成纤维细胞。这些细胞显示出细胞体积增大，但增殖、有丝分裂或凋亡没有变化。使用微阵列方法，我们能够鉴定出 Fbxl10 的潜在新靶基因，包括趋化因子、非编码 RNA Xist 和参与代谢过程的蛋白质。此外，我们发现 Fbxl10 被招募到 Ccl7、Xist、Crabp2 和 RipK3 的启动子上。Fbxl10 对启动子的占据伴随着 H3K4me3 水平的降低，但 H3K36me2 水平不变。此外，使用小干扰 RNA 方法敲低 Fbxl10 显示出 Fbxl10 靶基因的反向调节。总之，我们的数据揭示了 Fbxl10 在细胞形态、趋化因子表达和成纤维细胞代谢控制中的调节作用。
