Functional analysis of the transcription repressor PLU-1/JARID1B.
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The PLU-1/JARID1B nuclear protein, which is upregulated in breast cancers, belongs to the ARID family of DNA binding proteins and has strong transcriptional repression activity. To identify the target genes regulated by PLU-1/JARID1B, we overexpressed or silenced the human PLU-1/JARID1B gene in human mammary epithelial cells by using adenovirus and RNA interference systems, respectively, and then applied microarray analysis to identify candidate genes. A total of 100 genes showed inversely correlated differential expression in the two systems. Most of the candidate genes were downregulated by the overexpression of PLU-1/JARID1B, including the MT genes, the tumor suppressor gene BRCA1, and genes involved in the regulation of the M phase of the mitotic cell cycle. Chromatin immunoprecipitation assays confirmed that the metallothionein 1H (MT1H), -1F, and -1X genes are direct transcriptional targets of PLU-1/JARID1B in vivo. Furthermore, the level of trimethyl H3K4 of the MT1H promoter was increased following silencing of PLU-1/JARID1B. Both the PLU-1/JARID1B protein and the ARID domain selectively bound CG-rich DNA. The GCACA/C motif, which is abundant in metallothionein promoters, was identified as a consensus binding sequence of the PLU-1/JARID1B ARID domain. As expected from the microarray data, cells overexpressing PLU-1/JARID1B have an impaired G(2)/M checkpoint. Our study provides insight into the molecular function of the breast cancer-associated transcriptional repressor PLU-1/JARID1B. (+info)
The histone H3 lysine-27 demethylase Jmjd3 links inflammation to inhibition of polycomb-mediated gene silencing.
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Epigenetic chromatin marks restrict the ability of differentiated cells to change gene expression programs in response to environmental cues and to transdifferentiate. Polycomb group (PcG) proteins mediate gene silencing and repress transdifferentiation in a manner dependent on histone H3 lysine 27 trimethylation (H3K27me3). However, macrophages migrated into inflamed tissues can transdifferentiate, but it is unknown whether inflammation alters PcG-dependent silencing. Here we show that the JmjC-domain protein Jmjd3 is a H3K27me demethylase expressed in macrophages in response to bacterial products and inflammatory cytokines. Jmjd3 binds PcG target genes and regulates their H3K27me3 levels and transcriptional activity. The discovery of an inducible enzyme that erases a histone mark controlling differentiation and cell identity provides a link between inflammation and reprogramming of the epigenome, which could be the basis for macrophage plasticity and might explain the differentiation abnormalities in chronic inflammation. (+info)
LSD1 and the chemistry of histone demethylation.
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The recent discovery that histone demethylation can be catalyzed by the flavin-dependent amine oxidase LSD1 has ushered in a new chapter in the chromatin-remodeling community. Herein, we discuss the rapid progress of the histone demethylase field including the recent identification of the non-heme iron-dependent histone demethylases (JmjC family), the basis for LSD1 substrate site specificity and the newly emerging potential for inhibition of these enzymes in structural and functional analysis. (+info)
Succinate inhibition of alpha-ketoglutarate-dependent enzymes in a yeast model of paraganglioma.
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The tricarboxylic acid (TCA) cycle enzyme succinate dehydrogenase (SDH) is a tumor suppressor. Heterozygosity for defective SDH subunit genes predisposes to familial paraganglioma (PGL) or pheochromocytoma (PHEO). Models invoking reactive oxygen species (ROS) or succinate accumulation have been proposed to explain the link between TCA cycle dysfunction and oncogenesis. Here we study the biochemical consequences of a common familial PGL-linked mutation, loss of the SDHB subunit, in a yeast model. This strain has increased ROS production but no evidence of mutagenic DNA damage. Because the strain lacks SDH activity, succinate accumulates dramatically and inhibits alpha-ketoglutarate (alphaKG)-dependent enzyme Jlp1, involved in sulfur metabolism, and alphaKG-dependent histone demethylase Jhd1. We show that mammalian JmjC-domain histone demethylases are also vulnerable to succinate inhibition in vitro and in cultured cells. Our results suggest that any alphaKG-dependent enzyme is a potential target of accumulated succinate in oncogenesis. The possible role that inhibition of these enzymes by succinate may have in oncogenesis is discussed. (+info)
H3K27 demethylases, at long last.
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Methylation of lysine 27 on histone H3 (H3K27me) by the Polycomb complex (PRC2) proteins is associated with gene silencing in many developmental processes. A cluster of recent papers (Agger et al., 2007; De Santa et al., 2007; Lan et al., 2007; Lee et al., 2007) identify the JmjC-domain proteins UTX and JMJD3 as H3K27-specific demethylases that remove this methyl mark, enabling the activation of genes involved in animal body patterning and the inflammatory response. (+info)
JMJD3 is a histone H3K27 demethylase.
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Histone methylation is an important epigenetic phenomenon that participates in a diverse array of cellular processes and has been found to be associated with cancer. Recent identification of several histone demethylases has proved that histone methylation is a reversible process. Through a candidate approach, we have biochemically identified JMJD3 as an H3K27 demethylase. Transfection of JMJD3 into HeLa cells caused a specific reduction of trimethyl H3K27, but had no effect on di- and monomethyl H3K27, or histone lysine methylations on H3K4 and H3K9. The enzymatic activity requires the JmjC domain and the conserved histidine that has been suggested to be important for a cofactor binding. In vitro biochemical experiments demonstrated that JMJD3 directly catalyzes the demethylation. In addition, we found that JMJD3 is upregulated in prostate cancer, and its expression is higher in metastatic prostate cancer. Thus, we identified JMJD3 as a demethylase capable of removing the trimethyl group from histone H3 lysine 27 and upregulated in prostate cancer. (+info)
Jmjd1a and Jmjd2c histone H3 Lys 9 demethylases regulate self-renewal in embryonic stem cells.
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Embryonic stem (ES) cells are pluripotent cells with the ability to self-renew indefinitely. These unique properties are controlled by genetic factors and chromatin structure. The exit from the self-renewing state is accompanied by changes in epigenetic chromatin modifications such as an induction in the silencing-associated histone H3 Lys 9 dimethylation and trimethylation (H3K9Me2/Me3) marks. Here, we show that the H3K9Me2 and H3K9Me3 demethylase genes, Jmjd1a and Jmjd2c, are positively regulated by the ES cell transcription factor Oct4. Interestingly, Jmjd1a or Jmjd2c depletion leads to ES cell differentiation, which is accompanied by a reduction in the expression of ES cell-specific genes and an induction of lineage marker genes. Jmjd1a demethylates H3K9Me2 at the promoter regions of Tcl1, Tcfcp2l1, and Zfp57 and positively regulates the expression of these pluripotency-associated genes. Jmjd2c acts as a positive regulator for Nanog, which encodes for a key transcription factor for self-renewal in ES cells. We further demonstrate that Jmjd2c is required to reverse the H3K9Me3 marks at the Nanog promoter region and consequently prevents transcriptional repressors HP1 and KAP1 from binding. Our results connect the ES cell transcription circuitry to chromatin modulation through H3K9 demethylation in pluripotent cells. (+info)
JMJD6 is a histone arginine demethylase.
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Arginine methylation occurs on a number of proteins involved in a variety of cellular functions. Histone tails are known to be mono- and dimethylated on multiple arginine residues where they influence chromatin remodeling and gene expression. To date, no enzyme has been shown to reverse these regulatory modifications. We demonstrate that the Jumonji domain-containing 6 protein (JMJD6) is a JmjC-containing iron- and 2-oxoglutarate-dependent dioxygenase that demethylates histone H3 at arginine 2 (H3R2) and histone H4 at arginine 3 (H4R3) in both biochemical and cell-based assays. These findings may help explain the many developmental defects observed in the JMJD6(-/-) knockout mice. (+info)