Project description:This SuperSeries is composed of the following subset Series: GSE25444: Differential gene expression in ref6-1 GSE25446: Genome-wide comparison of H3K27me3 difference between ref6-1 and wild type Col Refer to individual Series
Project description:Understanding the mechanisms of epigenetic remodeling that follow fertilization is a fundamental step toward understanding the bases of early embryonic development and pluripotency. Extensive and dynamic chromatin remodeling is observed after fertilization, including DNA methylation and histone modifications. These changes underlie the transition from gametic to embryonic chromatin and are thought to facilitate embryonic genome activation. In particular, trimethylation of histone 3 lysine 27 (H3K27me3) is associated with gene-specific transcription repression. Global levels of this epigenetic mark are high in oocyte chromatin and decrease to minimal levels at the time of embryonic genome activation. We provide evidence that the decrease in H3K27me3 observed during early development is cell-cycle independent, suggesting an active mechanism for removal of this epigenetic mark. Among H3K27me3-specific demethylases, Jumonji domain-containing protein 3 (JMJD3), but not ubiquitously transcribed tetratricopeptide repeat X (UTX), present high transcript levels in oocytes. Soon after fertilization JMJD3 protein levels increase, concurrent with a decrease in mRNA levels. This pattern of expression suggests maternal inheritance of JMJD3. Knockdown of JMJD3 by siRNA injection in parthenogenetically activated metaphase II oocytes resulted in inhibition of the H3K27me3 decrease normally observed in preimplantation embryos. Moreover, knockdown of JMJD3 in oocytes reduced the rate of blastocyst development. Overall, these results indicate that JMJD3 is involved in active demethylation of H3K27me3 during early embryo development and that this mark plays an important role during the progression of embryos to blastocysts.
Project description:Covalent modifications of histones, such as acetylation and methylation, play important roles in the regulation of gene expression. Histone lysine methylation has been implicated in both gene activation and repression, depending on the specific lysine (K) residue that becomes methylated and the state of methylation (mono-, di-, or trimethylation). Methylation on K4, K9, and K36 of histone H3 has been shown to be reversible and can be removed by site-specific demethylases. However, the enzymes that antagonize methylation on K27 of histone H3 (H3K27), an epigenetic mark important for embryonic stem cell maintenance, Polycomb-mediated gene silencing, and X chromosome inactivation have been elusive. Here we show the JmjC domain-containing protein UTX (ubiquitously transcribed tetratricopeptide repeat, X chromosome), as well as the related JMJD3 (jumonji domain containing 3), specifically removes methyl marks on H3K27 in vitro. Further, the demethylase activity of UTX requires a catalytically active JmjC domain. Finally, overexpression of UTX and JMJD3 leads to reduced di- and trimethylation on H3K27 in cells, suggesting that UTX and JMJD3 may function as H3K27 demethylases in vivo. The identification of UTX and JMJD3 as H3K27-specific demethylases provides direct evidence to indicate that similar to methylation on K4, K9, and K36 of histone H3, methylation on H3K27 is also reversible and can be dynamically regulated by site-specific histone methyltransferases and demethylases.
Project description:Patterns of methylation at lysine 4 and 27 of histone H3 have been associated with states of gene activation and repression that are developmentally regulated and are thought to underlie the establishment of lineage specific gene expression programs. Recent studies have provided fundamental insight into the problem of lineage specification by comparing global changes in chromatin and transcription between ES and neural stem (NS) cells, points respectively of departure and arrival for neural commitment. With these maps of the differentiated state in place, a central task is now to unravel the chromatin dynamics that enables these differentiation transitions. In particular, the observation that lineage-specific genes repressed in ES cells by Polycomb-mediated H3-K27 trimethylation (H3-K27me3) are demethylated and derepressed in differentiated cells posited the existence of a specific H3-K27 demethylase.In order to gain insight into the epigenetic transitions that enable lineage specification, we investigated the early stages of neural commitment using as model system the monolayer differentiation of mouse ES cells into neural stem (NS) cells. Starting from a comprehensive profiling of JmjC-domain genes, we report here that Jmjd3, recently identified as a H3-K27me3 specific demethylase, controls the expression of key regulators and markers of neurogenesis and is required for commitment to the neural lineage.Our results demonstrate the relevance of an enzymatic activity that antagonizes Polycomb regulation and highlight different modalities through which the dynamics of H3-K27me3 is related to transcriptional output. By showing that the H3-K27 demethylase Jmjd3 is required for commitment to the neural lineage and that it resolves the bivalent domain at the Nestin promoter, our work confirms the functional relevance of bivalent domain resolution that had been posited on the basis of the genome-wide correlation between their controlled resolution and differentiation. In addition, our data indicate that the regulation of H3-K27me3 is highly gene- and context- specific, suggesting that the interplay of methyltransferases and demethylases enables the fine-tuning more than the on/off alternation of methylation states.
Project description:The early mammalian embryo utilizes histone H3 lysine 27 trimethylation (H3K27me3) to maintain essential developmental genes in a repressive chromatin state. As differentiation progresses, H3K27me3 is removed in a distinct fashion to activate lineage specific patterns of developmental gene expression. These rapid changes in early embryonic chromatin environment are thought to be dependent on H3K27 demethylases. We have taken a mouse genetics approach to remove activity of both H3K27 demethylases of the Kdm6 gene family, Utx (Kdm6a, X-linked gene) and Jmjd3 (Kdm6b, autosomal gene). Male embryos null for active H3K27 demethylation by the Kdm6 gene family survive to term. At mid-gestation, embryos demonstrate proper patterning and activation of Hox genes. These male embryos retain the Y-chromosome UTX homolog, UTY, which cannot demethylate H3K27me3 due to mutations in catalytic site of the Jumonji-C domain. Embryonic stem (ES) cells lacking all enzymatic KDM6 demethylation exhibit a typical decrease in global H3K27me3 levels with differentiation. Retinoic acid differentiations of these ES cells demonstrate loss of H3K27me3 and gain of H3K4me3 to Hox promoters and other transcription factors, and induce expression similar to control cells. A small subset of genes exhibit decreased expression associated with reduction of promoter H3K4me3 and some low-level accumulation of H3K27me3. Finally, Utx and Jmjd3 mutant mouse embryonic fibroblasts (MEFs) demonstrate dramatic loss of H3K27me3 from promoters of several Hox genes and transcription factors. Our results indicate that early embryonic H3K27me3 repression can be alleviated in the absence of active demethylation by the Kdm6 gene family.
Project description:The small GTPase RHOJ is a key regulator of breast cancer metastasis by promoting cell migration and invasion. The prometastatic stimulus TGF-β activates RHOJ transcription via megakaryocytic leukemia 1 (MKL1). The underlying epigenetic mechanism is not clear. Here, we report that MKL1 deficiency led to disrupted assembly of the RNA polymerase II preinitiation complex on the RHOJ promoter in breast cancer cells. This could be partially explained by histone H3K9/H3K27 methylation status. Further analysis confirmed that the H3K9/H3K27 dual demethylase JHDM1D/KDM7A was essential for TGF-β-induced RHOJ transcription in breast cancer cells. MKL1 interacted with and recruited KDM7A to the RHOJ promoter to cooperatively activate RHOJ transcription. KDM7A knockdown attenuated migration and invasion of breast cancer cells in vitro and mitigated the growth and metastasis of breast cancer cells in nude mice. KDM7A expression level, either singularly or in combination with that of RHOJ, could be used to predict prognosis in breast cancer patients. Of interest, KDM7A appeared to be a direct transcriptional target of TGF-β signaling. A SMAD2/SMAD4 complex bound to the KDM7A promoter and mediated TGF-β-induced KDM7A transcription. In conclusion, our data unveil a novel epigenetic mechanism whereby TGF-β regulates the transcription of the prometastatic small GTPase RHOJ. Screening for small-molecule inhibitors of KDM7A may yield effective therapeutic solutions to treat malignant breast cancers.
Project description:The KDM5/JARID1 family of Fe(II)- and ?-ketoglutarate-dependent demethylases remove methyl groups from tri- and dimethylated lysine 4 of histone H3. Accumulating evidence from primary tumors and model systems supports a role for KDM5A (JARID1A/RBP2) and KDM5B (JARID1B/PLU1) as oncogenic drivers. The KDM5 family is unique among the Jumonji domain-containing histone demethylases in that there is an atypical insertion of a DNA-binding ARID domain and a histone-binding PHD domain into the Jumonji domain, which separates the catalytic domain into two fragments (JmjN and JmjC). Here we demonstrate that internal deletion of the ARID and PHD1 domains has a negligible effect on in vitro enzymatic kinetics of the KDM5 family of enzymes. We present a crystal structure of the linked JmjN-JmjC domain from KDM5A, which reveals that the linked domain fully reconstitutes the cofactor (metal ion and ?-ketoglutarate) binding characteristics of other structurally characterized Jumonji domain demethylases. Docking studies with GSK-J1, a selective inhibitor of the KDM6/KDM5 subfamilies, identify critical residues for binding of the inhibitor to the reconstituted KDM5 Jumonji domain. Further, we found that GSK-J1 inhibited the demethylase activity of KDM5C with 8.5-fold increased potency compared with that of KDM5B at 1 mm ?-ketoglutarate. In contrast, JIB-04 (a pan-inhibitor of the Jumonji demethylase superfamily) had the opposite effect and was ~8-fold more potent against KDM5B than against KDM5C. Interestingly, the relative selectivity of JIB-04 toward KDM5B over KDM5C in vitro translates to a ~10-50-fold greater growth-inhibitory activity against breast cancer cell lines. These data define the minimal requirements for enzymatic activity of the KDM5 family to be the linked JmjN-JmjC domain coupled with the immediate C-terminal helical zinc-binding domain and provide structural characterization of the linked JmjN-JmjC domain for the KDM5 family, which should prove useful in the design of KDM5 demethylase inhibitors with improved potency and selectivity.
Project description:Histone demethylases-both lysine-specific demethylase 1 (LSD1) and Jumonji-C (JmjC) domain-containing proteins-are broadly implicated in the regulation of chromatin-dependent processes. In Arabidopsis thaliana, histone marks directly affect DNA methylation, and mutations in LSD1 homologues show reduced DNA methylation at some loci. We screened transfer DNA mutations in genes encoding JmjC domains for defects in DNA methylation. Mutations in jmj14 result in reduced DNA methylation in non-CG contexts at targets of DRM2 (domains rearranged methyltransferase 2)-mediated RNA-directed DNA methylation (RdDM), which is associated with an increase in H3K4m3. Unlike other components of RdDM, JMJ14 is not required for de novo methylation of a transgene, suggesting that JMJ14 is specifically involved in the maintenance phase of DRM2-mediated RdDM.
Project description:In higher eukaryotes, up to 70% of genes have high levels of nonmethylated cytosine/guanine base pairs (CpGs) surrounding promoters and gene regulatory units. These features, called CpG islands, were identified over 20 years ago, but there remains little mechanistic evidence to suggest how these enigmatic elements contribute to promoter function, except that they are refractory to epigenetic silencing by DNA methylation. Here we show that CpG islands directly recruit the H3K36-specific lysine demethylase enzyme KDM2A. Nucleation of KDM2A at these elements results in removal of H3K36 methylation, creating CpG island chromatin that is uniquely depleted of this modification. KDM2A utilizes a zinc finger CxxC (ZF-CxxC) domain that preferentially recognizes nonmethylated CpG DNA, and binding is blocked when the CpG DNA is methylated, thus constraining KDM2A to nonmethylated CpG islands. These data expose a straightforward mechanism through which KDM2A delineates a unique architecture that differentiates CpG island chromatin from bulk chromatin.