Project description:FOXA1 is a pioneer factor that is important in hormone dependent cancer cells to stabilise nuclear receptors, such as estrogen receptor (ER) to chromatin. FOXA1 binds to enhancers regions that are enriched in H3K4mono- and dimethylation (H3K4me1, H3K4me2) histone marks and evidence suggests that these marks are requisite events for FOXA1 to associate with enhancers to initate subsequent gene expression events. However, exogenous expression of FOXA1 has been shown to induce H3K4me1 and H3K4me2 signal at enhancer elements and the order of events and the functional importance of these events is not clear. We performed a FOXA1 Rapid Immunoprecipitation Mass Spectrometry of Endogenous Proteins (RIME) screen in ERα-positive MCF-7 breast cancer cells in order to identify FOXA1 interacting partners and we found histone-lysine N-methyltransferase (MLL3) as the top FOXA1 interacting protein. MLL3 is typically thought to induce H3K4me3 at promoter regions, but recent findings suggest it may contribute to H3K4me1 deposition, in line with our observation that MLL3 associates with an enhancer specific protein. We performed MLL3 ChIP-seq in breast cancer cells and unexpectedly found that MLL3 binds mostly at non-promoter regions enhancers, in contrast to the prevailing hypothesis. MLL3 was shown to occupy regions marked by FOXA1 occupancy and as expected, H3K4me1 and H3K4me2. MLL3 binding was dependent on FOXA1, indicating that FOXA1 recruits MLL3 to chromatin. Motif analysis and subsequent genomic mapping revealed a role for Grainy head like protein-2 (GRHL2) which was shown to co-occupy regions of the chromatin with MLL3. Regions occupied by all three factors, namely FOXA1, MLL3 and GRHL2, were most enriched in H3K4me1. MLL3 silencing decreased H3K4me1 at enhancer elements, but had no appreciable impact on H3K4me3 at enhancer elements. We identify a complex relationship between FOXA1, MLL3 and H3K4me1 at enhancers in breast cancer and propose a mechanism whereby the pioneer factor FOXA1 can interact with a chromatin modifier MLL3, recruiting it to chromatin to facilitate the deposition of H3K4me1 histone marks, subsequently demarcating active enhancer elements.
Project description:Enhancers play a key role in regulating cell type-specific gene expression and are marked by histone modifications such as methylation and acetylation. Mono-methylation of lysine 4 on histone H3 (H3K4me1) initially primes enhancers, preceding enhancer activation via acetylation of lysine 27 on histone H3 (H3K27ac). MLL4 is a major enhancer H3K4 mono-methyltransferase with partial functional redundancy with MLL3. However, how H3K4me1 affects enhancer regulation in cell differentiation has remained unclear. By screening several lysine-to-methionine mutants of H3.3, we first found that depletion of H3K4 methylation by H3.3K4M mutation severely impairs adipogenesis in culture. Using tissue-specific expression of H3.3K4M in mice, we further demonstrate that H3.3K4M inhibits adipose tissue and muscle development in vivo. Mechanistically, H3.3K4M destabilizes MLL3/4 proteins but not other members of the mammalian Set1-like H3K4 methyltransferase family and prevents MLL3/4-mediated enhancer activation in adipogenesis. Using tissue-specific deletion of the enzymatic SET domain of MLL3/4 in mice, we also show that deletion of the SET domain prevents adipose tissue and muscle development in vivo and inhibits adipogenesis by destabilizing MLL3/4 in vitro. Notably, H3.3K4M expression mimics MLL3/4 SET domain deletion in preventing adipogenesis. Interestingly, H3.3K4M does not affect adipose tissue maintenance and function, suggesting that MLL3/4-mediated H3K4 methylation is dispensable for the maintenance and function of differentiated adipocytes. Together, our findings suggest that H3.3K4M targets MLL3/4 to prevent enhancer activation in adipogenesis.
Project description:Mono-methylation of histone H3 on lysine 4 (H3K4me1) and acetylation of histone H3 on lysine 27 (H3K27ac) are histone modifications that are highly enriched over the body of actively transcribed genes and enhancers. Although in yeast all H3K4 methylation patterns including H3K4me1 are implemented by Set1/COMPASS, there are three classes of COMPASS-like complexes in Drosophila that could carry out H3K4me1 on enhancers: dSet1, Trithorax and Trithorax-related (Trr). Here, we report that Trr, the Drosophila homolog of mammalian Mll3/4, can function as a major H3K4 mono-methyltransferase on enhancers in vivo. Loss of Trr results in a global decrease of H3K4me1 and H3K27ac in various tissues. Assays with the cut wing margin enhancer imply a functional role for Trr in enhancer-mediated processes. A genome-wide analysis demonstrates that Trr is required for H3K4me1 and H3K27ac on chromatin signatures that resemble the histone modification patterns described for enhancers. Since Trr and mammalian Mll3/4 complexes are distinguished by bearing a unique subunit, the H3K27 demethylase UTX, we propose a model in which the H3K4 mono-methyltransferase Trr, and the H3K27 demethylase, UTX, cooperate to regulate the transition from inactive/poised to active enhancers. ChIP-seq of Trr, LPT, UTX in Drosophila S2 Cells. ChIP-seq of H3K4me1, H3K4me3, H3K27ac, H3K27me3 in WT and Trr knock-down Drosophila S2 cells. ChIP-seq of H3K4me1, H3K27me3 in LPT knock-down Drosophila S2 cells. ChIP-seq of LPT and UTX in Trr knock-down Drosophila S2 cells. ChIP-seq of H3K4me1 and H3K27me3 in MLL1(+/+), MLL1(-/-), MLL3(+/+), and MLL3(-/-) Mouse Embryonic Fibroblasts (MEFs).
Project description:Histone H3 lysine 4 (H3K4) can be mono-, di-, and trimethylated by members of the COMPASS (COMplex of Proteins ASsociated with Set1) family from yeast to human and these modifications can be found at distinct regions of the genome. Monomethylation of histone H3K4 (H3K4me1) is relatively more enriched at metazoan enhancer regions compared to trimethylated histone H3K4 (H3K4me3), which are found at transcription start sites in all eukaryotes. Our recent studies in Drosophila demonstrated that the Trithorax-related (Trr) branch of the COMPASS family regulates enhancer activity and is responsible for the implementation of H3K4me1 at these regions. There are six COMPASS family members in mammals, two of which, MLL3 and MLL4, are most closely related to Drosophila Trr. Here, we use ChIP-seq of this class of COMPASS family members in both human HCT116 cells and mouse embryonic stem cells and find that MLL4 is preferentially found at enhancer regions. MLL3 and MLL4 are frequently mutated in cancer, and indeed, the widely used HCT116 cancer cell line contains inactivating mutations in the MLL3 gene. Using HCT116 cells in which MLL4 has also been knocked out, we demonstrate that MLL4 is a major regulator of H3K4me1 in these cells, with the greatest loss of monomethylation at enhancer regions. Moreover, we found a redundant role between Mll3 and Mll4 in enhancer H3K4 monomethylation in mouse embryonic fibroblast (MEF) cells. These findings suggest that mammalian MLL3/MLL4 function in the regulation of enhancer activity and enhancer-promoter communication during gene expression and that mutations of MLL3 and MLL4 found in cancer could exert their properties through enhancer malfunction. ChIP-Seq in mouse embryonic stem (mES) cells for MLL4. ChIP-seq of MLL4 and p300 in human parental HCT116 cells. ChIP-seq of H3K4me1, H3K4me2 and H3K4me3 in parental HCT116 cells and HCT116 cells with Mll4∆set.
Project description:Enhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for the deposition of H3K4me1/2 on enhancers remain elusive. Furthermore, the functions of these methyltransferases on enhancers and associated cell-type-specific gene expression are poorly understood. Here, we identify MLL4 (KMT2D) as a major H3K4 mono- and di-methyltransferase in mammalian cells. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 dramatically decreases H3K4me1/2 and H3K27ac on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Finally, we provide evidence that lineage-determining TFs recruit and require MLL4 to establish enhancers critical for cell-type-specific gene expression. Together, these results identify MLL4 as an H3K4 mono-/di-methyltransferase required for enhancer activation during cell differentiation. ChIP-Seq analyses of adipogenic TF (C/EBPalpha, C/EBPbeta, and PPARgamma) and Pol II profiles at D0 (day 0) and D2 (day 2) of adipogenesis in WT (MLL3-/-) and MLL4 KO (MLL3-/-;MLL4-/-) brown preadipocytes.
Project description:Enhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for the deposition of H3K4me1/2 on enhancers remain elusive. Furthermore, the functions of these methyltransferases on enhancers and associated cell-type-specific gene expression are poorly understood. Here, we identify MLL4 (KMT2D) as a major H3K4 mono- and di-methyltransferase in mammalian cells. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 dramatically decreases H3K4me1/2 and H3K27ac on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Finally, we provide evidence that lineage-determining TFs recruit and require MLL4 to establish enhancers critical for cell-type-specific gene expression. Together, these results identify MLL4 as an H3K4 mono-/di-methyltransferase required for enhancer activation during cell differentiation. ChIP-Seq analyses of histone modifications (H3K4me1, H3K4me2, H3K4me3, and H3K27ac) at D0 (day 0) and D2 (day 2) of adipogenesis in WT (MLL3-/-) and MLL4 KO (MLL3-/-;MLL4-/-) brown preadipocytes.
Project description:Enhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for the deposition of H3K4me1/2 on enhancers remain elusive. Furthermore, the functions of these methyltransferases on enhancers and associated cell-type-specific gene expression are poorly understood. Here, we identify MLL4 (KMT2D) as a major H3K4 mono- and di-methyltransferase in mammalian cells. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 dramatically decreases H3K4me1/2 and H3K27ac on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Finally, we provide evidence that lineage-determining TFs recruit and require MLL4 to establish enhancers critical for cell-type-specific gene expression. Together, these results identify MLL4 as an H3K4 mono-/di-methyltransferase required for enhancer activation during cell differentiation. RNA-Seq analyses of mRNA profiles at D0 (day 0) and D2 (day 2) of adipogenesis in WT (MLL3-/-) and MLL4 KO (MLL3-/-;MLL4-/-) brown preadipocytes.
Project description:Enhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for the deposition of H3K4me1/2 on enhancers remain elusive. Furthermore, the functions of these methyltransferases on enhancers and associated cell-type-specific gene expression are poorly understood. Here, we identify MLL4 (KMT2D) as a major H3K4 mono- and di-methyltransferase in mammalian cells. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 dramatically decreases H3K4me1/2 and H3K27ac on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Finally, we provide evidence that lineage-determining TFs recruit and require MLL4 to establish enhancers critical for cell-type-specific gene expression. Together, these results identify MLL4 as an H3K4 mono-/di-methyltransferase required for enhancer activation during cell differentiation. ChIP-Seq analyses of MLL4 binding profiles at D0 (day 0), D2 (day 2), and D7 (day 7) of adipogenesis in WT (MLL3-/-) and MLL4 KO (MLL3-/-;MLL4-/-) brown preadipocytes. D0 and D2 input DNA samples can be found in GSE50417.
Project description:Histone H3 lysine 4 monomethylation (H3K4me1) is an evolutionarily conserved feature of enhancer chromatin catalyzed by the COMPASS-like methyltransferase family that includes Trr in Drosophila melanogaster and MLL3 (encoded by KMT2C) and MLL4 (encoded by KMT2D) in mammals. Here we demonstrate that Drosophila embryos expressing catalytically deficient Trr eclose and develop to productive adulthood. Parallel experiments with a trr allele that augments enzyme product specificity show that conversion of H3K4me1 at enhancers to H3K4me2 and H3K4me3 is also compatible with life and results in minimal changes in gene expression. Similarly, loss of the catalytic SET domains of MLL3 and MLL4 in mouse embryonic stem cells (mESCs) does not disrupt selfrenewal. Drosophila embryos with trr alleles encoding catalytic mutants manifest subtle developmental abnormalities when subjected to temperature stress or altered cohesin levels. Collectively, our findings suggest that animal development can occur in the context of Trr or mammalian COMPASS-like proteins deficient in H3K4 monomethylation activity and point to a possible role for H3K4me1 on cis-regulatory elements in specific settings to fine-tune transcriptional regulation in response to environmental stress.
Project description:Aberrant expression of homeobox transcription factor HOXA9 is a central component of the leukemogenic program driven by diverse oncogenes. Here we show that HOXA9 overexpression in myeloid progenitor cells and pro-B cells leads to significant rearrangement of the epigenetic landscape with prominent emergence of cancer specific de novo enhancers. HOXA9 acts as a pioneer factor at the de novo enhancers and is required for recruitment of transcription factor CEBP/a and the histone H3K4 methyltransferase MLL3/MLL4 complex. HOXA9 function at the de novo enhancer is distinct from its physiological role at distal enhancers during normal hematopoietic development. Genetic deletion of MLL3/4 specifically affects the active enhancer signatures at de novo enhancers and inhibits HOXA9/MEIS1-mediated leukemogenesis. Our study reveals a previously uncharacterized role of HOXA9 and the MLL3/4 complex in leukemogenesis and provide mechanistic insights in epigenetic deregulation during malignant transformation.