RESUMEN
The mitotic deacetylase complex MiDAC has recently been shown to play a vital physiological role in embryonic development and neurite outgrowth. However, how MiDAC functionally intersects with other chromatin-modifying regulators is poorly understood. Here, we describe a physical interaction between the histone H3K27 demethylase UTX, a complex-specific subunit of the enhancer-associated MLL3/4 complexes, and MiDAC. We demonstrate that UTX bridges the association of the MLL3/4 complexes and MiDAC by interacting with ELMSAN1, a scaffolding subunit of MiDAC. Our data suggest that MiDAC constitutes a negative genome-wide regulator of H4K20ac, an activity which is counteracted by the MLL3/4 complexes. MiDAC and the MLL3/4 complexes co-localize at many genomic regions, which are enriched for H4K20ac and the enhancer marks H3K4me1, H3K4me2, and H3K27ac. We find that MiDAC antagonizes the recruitment of UTX and MLL4 and negatively regulates H4K20ac, and to a lesser extent H3K4me2 and H3K27ac, resulting in transcriptional attenuation of associated genes. In summary, our findings provide a paradigm how the opposing roles of chromatin-modifying components, such as MiDAC and the MLL3/4 complexes, balance the transcriptional output of specific gene expression programs.
Asunto(s)
Elementos de Facilitación Genéticos , Histonas , Cromatina/genética , Elementos de Facilitación Genéticos/genética , Expresión Génica , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/genética , Histonas/metabolismoRESUMEN
DNA methylation at enhancers and CpG islands usually leads to gene repression, which is counteracted by DNA demethylation through the TET protein family. However, how TET enzymes are recruited and regulated at these genomic loci is not fully understood. Here, we identify TET2, the glycosyltransferase OGT and a previously undescribed proline and serine rich protein, PROSER1 as interactors of UTX, a component of the enhancer-associated MLL3/4 complexes. We find that PROSER1 mediates the interaction between OGT and TET2, thus promoting TET2 O-GlcNAcylation and protein stability. In addition, PROSER1, UTX, TET1/2, and OGT colocalize on many genomic elements genome-wide. Loss of PROSER1 results in lower enrichment of UTX, TET1/2, and OGT at enhancers and CpG islands, with a concomitant increase in DNA methylation and transcriptional down-regulation of associated target genes and increased DNA hypermethylation encroachment at H3K4me1-predisposed CpG islands. Furthermore, we provide evidence that PROSER1 acts as a more general regulator of OGT activity by controlling O-GlcNAcylation of multiple other chromatin signaling pathways. Taken together, this study describes for the first time a regulator of TET2 O-GlcNAcylation and its implications in mediating DNA demethylation at UTX-dependent enhancers and CpG islands and supports an important role for PROSER1 in regulating the function of various chromatin-associated proteins via OGT-mediated O-GlcNAcylation.
Asunto(s)
Islas de CpG , Desmetilación del ADN , Proteínas de Unión al ADN/metabolismo , Dioxigenasas/metabolismo , Elementos de Facilitación Genéticos , Histona Demetilasas/metabolismo , Animales , Línea Celular , Cromatina/genética , Cromatina/metabolismo , Secuenciación de Inmunoprecipitación de Cromatina , Biología Computacional/métodos , Técnicas de Silenciamiento del Gen , Glicosilación , N-Metiltransferasa de Histona-Lisina/metabolismo , Humanos , Ratones , Modelos Biológicos , Unión Proteica , Transporte de ProteínasRESUMEN
The mitotic deacetylase complex (MiDAC) is a recently identified histone deacetylase (HDAC) complex. While other HDAC complexes have been implicated in neurogenesis, the physiological role of MiDAC remains unknown. Here, we show that MiDAC constitutes an important regulator of neural differentiation. We demonstrate that MiDAC functions as a modulator of a neurodevelopmental gene expression program and binds to important regulators of neurite outgrowth. MiDAC upregulates gene expression of pro-neural genes such as those encoding the secreted ligands SLIT3 and NETRIN1 (NTN1) by a mechanism suggestive of H4K20ac removal on promoters and enhancers. Conversely, MiDAC inhibits gene expression by reducing H3K27ac on promoter-proximal and -distal elements of negative regulators of neurogenesis. Furthermore, loss of MiDAC results in neurite outgrowth defects that can be rescued by supplementation with SLIT3 and/or NTN1. These findings indicate a crucial role for MiDAC in regulating the ligands of the SLIT3 and NTN1 signaling axes to ensure the proper integrity of neurite development.
Asunto(s)
Regulación de la Expresión Génica/fisiología , Histona Desacetilasas/metabolismo , Proyección Neuronal/fisiología , Animales , Diferenciación Celular/fisiología , Metilación de ADN/fisiología , Masculino , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Netrina-1/metabolismoRESUMEN
Histone H3 Lys4 (H3K4) methylation is a chromatin feature enriched at gene cis-regulatory sequences such as promoters and enhancers. Here we identify an evolutionarily conserved factor, BRWD2/PHIP, which colocalizes with histone H3K4 methylation genome-wide in human cells, mouse embryonic stem cells, and Drosophila Biochemical analysis of BRWD2 demonstrated an association with the Cullin-4-RING ubiquitin E3 ligase-4 (CRL4) complex, nucleosomes, and chromatin remodelers. BRWD2/PHIP binds directly to H3K4 methylation through a previously unidentified chromatin-binding module related to Royal Family Tudor domains, which we named the CryptoTudor domain. Using CRISPR-Cas9 genetic knockouts, we demonstrate that COMPASS H3K4 methyltransferase family members differentially regulate BRWD2/PHIP chromatin occupancy. Finally, we demonstrate that depletion of the single Drosophila homolog dBRWD3 results in altered gene expression and aberrant patterns of histone H3 Lys27 acetylation at enhancers and promoters, suggesting a cross-talk between these chromatin modifications and transcription through the BRWD protein family.
Asunto(s)
Drosophila melanogaster/genética , Regulación de la Expresión Génica , Histonas/metabolismo , Dominio Tudor , Acetilación , Animales , Sistemas CRISPR-Cas , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Elementos de Facilitación Genéticos , Epigénesis Genética , Técnicas de Inactivación de Genes , Histona Metiltransferasas , N-Metiltransferasa de Histona-Lisina/metabolismo , Humanos , Metilación , Ratones , Regiones Promotoras Genéticas , Unión Proteica/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Histone H3 lysine 4 monomethylation (H3K4me1) is an evolutionarily conserved feature of enhancer chromatin catalyzed by the COMPASS-like methyltransferase family, which 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 self-renewal. 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.
Asunto(s)
Proteínas de Drosophila/genética , Drosophila melanogaster/crecimiento & desarrollo , Elementos de Facilitación Genéticos , Regulación del Desarrollo de la Expresión Génica , N-Metiltransferasa de Histona-Lisina/genética , Histonas/genética , Secuencia de Aminoácidos , Animales , Baculoviridae/genética , Sistemas CRISPR-Cas , Cromatina/química , Cromatina/metabolismo , Proteínas de Drosophila/deficiencia , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Embrión no Mamífero , N-Metiltransferasa de Histona-Lisina/deficiencia , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/metabolismo , Larva/genética , Larva/crecimiento & desarrollo , Larva/metabolismo , Metilación , Ratones , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Células Sf9 , SpodopteraRESUMEN
Mutations in enhancer-associated chromatin-modifying components and genomic alterations in non-coding regions of the genome occur frequently in cancer, and other diseases pointing to the importance of enhancer fidelity to ensure proper tissue homeostasis. In this review, I will use specific examples to discuss how mutations in chromatin-modifying factors might affect enhancer activity of disease-relevant genes. I will then consider direct evidence from single nucleotide polymorphisms, small insertions, or deletions but also larger genomic rearrangements such as duplications, deletions, translocations, and inversions of specific enhancers to demonstrate how they have the ability to impact enhancer activity of disease genes including oncogenes and tumor suppressor genes. Considering that the scientific community only fairly recently has begun to focus its attention on "enhancer malfunction" in disease, I propose that multiple new enhancer-regulated and disease-relevant processes will be uncovered in the near future that will constitute the mechanistic basis for novel therapeutic avenues.
Asunto(s)
Elementos de Facilitación Genéticos , Regulación Neoplásica de la Expresión Génica , Mutación , Neoplasias/genética , Animales , Genes Relacionados con las Neoplasias , HumanosRESUMEN
Polycomb response elements (PREs) are specific DNA sequences that stably maintain the developmental pattern of gene expression. Drosophila PREs are well characterized, whereas the existence of PREs in mammals remains debated. Accumulating evidence supports a model in which CpG islands recruit Polycomb group (PcG) complexes; however, which subset of CGIs is selected to serve as PREs is unclear. Trithorax (Trx) positively regulates gene expression in Drosophila and co-occupies PREs to antagonize Polycomb-dependent silencing. Here we demonstrate that Trx-dependent H3K4 dimethylation (H3K4me2) marks Drosophila PREs and maintains the developmental expression pattern of nearby genes. Similarly, the mammalian Trx homolog, MLL1, deposits H3K4me2 at CpG-dense regions that could serve as PREs. In the absence of MLL1 and H3K4me2, H3K27me3 levels, a mark of Polycomb repressive complex 2 (PRC2), increase at these loci. By inhibiting PRC2-dependent H3K27me3 in the absence of MLL1, we can rescue expression of these loci, demonstrating a functional balance between MLL1 and PRC2 activities at these sites. Thus, our study provides rules for identifying cell-type-specific functional mammalian PREs within the human genome.
Asunto(s)
Proteínas Cromosómicas no Histona/genética , Neoplasias Colorrectales/genética , Islas de CpG , Metilación de ADN , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Evolución Molecular , N-Metiltransferasa de Histona-Lisina/genética , Proteína de la Leucemia Mieloide-Linfoide/genética , Complejo Represivo Polycomb 2/genética , Complejo Represivo Polycomb 2/metabolismo , Elementos de Respuesta , Animales , Proteínas Cromosómicas no Histona/metabolismo , Neoplasias Colorrectales/metabolismo , Neoplasias Colorrectales/patología , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Regulación del Desarrollo de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Células HCT116 , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Proteína de la Leucemia Mieloide-Linfoide/metabolismo , Interferencia de ARN , Especificidad de la Especie , Transcripción Genética , TransfecciónRESUMEN
Histone H3 lysine(27)-to-methionine (H3K27M) gain-of-function mutations occur in highly aggressive pediatric gliomas. We established a Drosophila animal model for the pathogenic histone H3K27M mutation and show that its overexpression resembles polycomb repressive complex 2 (PRC2) loss-of-function phenotypes, causing derepression of PRC2 target genes and developmental perturbations. Similarly, an H3K9M mutant depletes H3K9 methylation levels and suppresses position-effect variegation in various Drosophila tissues. The histone H3K9 demethylase KDM3B/JHDM2 associates with H3K9M-containing nucleosomes, and its misregulation in Drosophila results in changes of H3K9 methylation levels and heterochromatic silencing defects. We have established histone lysine-to-methionine mutants as robust in vivo tools for inhibiting methylation pathways that also function as biochemical reagents for capturing site-specific histone-modifying enzymes, thus providing molecular insight into chromatin signaling pathways.
Asunto(s)
Cromatina/metabolismo , Histonas/genética , Lisina/genética , Metionina/genética , Sustitución de Aminoácidos , Animales , Modelos Animales de Enfermedad , Proteínas de Drosophila/genética , Drosophila melanogaster , Silenciador del Gen , Glioma/genética , Glioma/metabolismo , Heterocromatina/metabolismo , N-Metiltransferasa de Histona-Lisina/genética , Histonas/metabolismo , Histona Demetilasas con Dominio de Jumonji/metabolismo , Metilación , Mutación , Transducción de SeñalRESUMEN
Why certain point mutations in a general transcription factor are associated with specific forms of cancer has been a major question in cancer biology. Enhancers are DNA regulatory elements that are key regulators of tissue-specific gene expression. Recent studies suggest that enhancer malfunction through point mutations in either regulatory elements or factors modulating enhancer-promoter communication could be the cause of tissue-specific cancer development. In this Perspective, we will discuss recent findings in the identification of cancer-related enhancer mutations and the role of Drosophila Trr and its human homologs, the MLL3 and MLL4/COMPASS-like complexes, as enhancer histone H3 lysine 4 (H3K4) monomethyltransferases functioning in enhancer-promoter communication. Recent genome-wide studies in the cataloging of somatic mutations in cancer have identified mutations in intergenic sequences encoding regulatory elements-and in MLL3 and MLL4 in both hematological malignancies and solid tumors. We propose that cancer-associated mutations in MLL3 and MLL4 exert their properties through the malfunction of Trr/MLL3/MLL4-dependent enhancers.
Asunto(s)
Proteínas de Unión al ADN/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Elementos de Facilitación Genéticos , Regulación Neoplásica de la Expresión Génica , N-Metiltransferasa de Histona-Lisina/genética , Neoplasias/genética , Animales , Transformación Celular Neoplásica/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , N-Metiltransferasa de Histona-Lisina/metabolismo , Humanos , Neoplasias/metabolismo , Mutación Puntual , Transducción de Señal , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Histone H3 lysine 4 (H3K4) can be mono-, di-, and trimethylated by members of the COMPASS (complex of proteins associated with Set1) family from Saccharomyces cerevisiae to humans, 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 is enriched at transcription start sites in all eukaryotes. Our recent studies of Drosophila melanogaster 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 (GeneID 58508) and MLL4 (GeneID 8085), are most closely related to Drosophila Trr. Here, we use chromatin immunoprecipitation-sequencing (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 MLL3 and MLL4 are major regulators of H3K4me1 in these cells, with the greatest loss of monomethylation at enhancer regions. Moreover, we find a redundant role between Mll3 (GeneID 231051) and Mll4 (GeneID 381022) in enhancer H3K4 monomethylation in mouse embryonic fibroblast (MEF) cells. These findings suggest that mammalian MLL3 and MLL4 function in the regulation of enhancer activity and that mutations of MLL3 and MLL4 that are found in cancers could exert their properties through malfunction of these Trr/MLL3/MLL4-specific (Trrific) enhancers.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Elementos de Facilitación Genéticos , Histonas/metabolismo , Procesamiento Proteico-Postraduccional , Animales , Epigénesis Genética , Expresión Génica , Células HCT116 , N-Metiltransferasa de Histona-Lisina , Humanos , Metilación , Ratones , Neoplasias/genética , Neoplasias/metabolismo , Transporte de ProteínasRESUMEN
Adult stem cells reside in microenvironments called niches, where they are regulated by both extrinsic cues, such as signaling from neighboring cells, and intrinsic factors, such as chromatin structure. Here we report that in the Drosophila testis niche an H3K27me3-specific histone demethylase encoded by Ubiquitously transcribed tetratricopeptide repeat gene on the X chromosome (dUTX) maintains active transcription of the Suppressor of cytokine signaling at 36E (Socs36E) gene by removing the repressive H3K27me3 modification near its transcription start site. Socs36E encodes an inhibitor of the Janus kinase signal transducer and activator of transcription (JAK-STAT) signaling pathway. Whereas much is known about niche-to-stem cell signaling, such as the JAK-STAT signaling that is crucial for stem cell identity and activity, comparatively little is known about signaling from stem cells to the niche. Our results reveal that stem cells send feedback to niche cells to maintain the proper gene expression and architecture of the niche. We found that dUTX acts in cyst stem cells to maintain gene expression in hub cells through activating Socs36E transcription and preventing hyperactivation of JAK-STAT signaling. dUTX also acts in germline stem cells to maintain hub structure through regulating DE-Cadherin levels. Therefore, our findings provide new insights into how an epigenetic factor regulates crosstalk among different cell types within an endogenous stem cell niche, and shed light on the biological functions of a histone demethylase in vivo.
Asunto(s)
Proteínas de Drosophila/fisiología , Regulación del Desarrollo de la Expresión Génica , Quinasas Janus/antagonistas & inhibidores , Oxidorreductasas N-Desmetilantes/fisiología , Factores de Transcripción STAT/antagonistas & inhibidores , Nicho de Células Madre/genética , Testículo/citología , Células Madre Adultas/citología , Células Madre Adultas/metabolismo , Células Madre Adultas/fisiología , Animales , Animales Modificados Genéticamente , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Células Germinativas/citología , Células Germinativas/metabolismo , Células Germinativas/fisiología , Histona Demetilasas/fisiología , Quinasas Janus/metabolismo , Masculino , Modelos Biológicos , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Factores de Transcripción STAT/metabolismo , Transducción de Señal/genética , Nicho de Células Madre/fisiología , Testículo/metabolismo , Testículo/fisiologíaRESUMEN
Monomethylation of histone H3 on Lys 4 (H3K4me1) and acetylation of histone H3 on Lys 27 (H3K27ac) are histone modifications that are highly enriched over the body of actively transcribed genes and on enhancers. Although in yeast all H3K4 methylation patterns, including H3K4me1, are implemented by Set1/COMPASS (complex of proteins associated with Set1), 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 the mammalian Mll3/4 COMPASS-like complexes, can function as a major H3K4 monomethyltransferase on enhancers in vivo. Loss of Trr results in a global decrease of H3K4me1 and H3K27ac levels in various tissues. Assays with the cut wing margin enhancer implied a functional role for Trr in enhancer-mediated processes. A genome-wide analysis demonstrated that Trr is required to maintain the H3K4me1 and H3K27ac chromatin signature that resembles the histone modification patterns described for enhancers. Furthermore, studies in the mammalian system suggested a role for the Trr homolog Mll3 in similar processes. 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 monomethyltransferases Trr/Mll3/Mll4 and the H3K27 demethylase UTX cooperate to regulate the transition from inactive/poised to active enhancers.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , Drosophila melanogaster/genética , Elementos de Facilitación Genéticos , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/metabolismo , Animales , Línea Celular , Proteínas de Drosophila/genética , Estudio de Asociación del Genoma Completo , N-Metiltransferasa de Histona-Lisina/genética , MetilaciónRESUMEN
Jarid2 was recently identified as an important component of the mammalian Polycomb repressive complex 2 (PRC2), where it has a major effect on PRC2 recruitment in mouse embryonic stem cells. Although Jarid2 is conserved in Drosophila, it has not previously been implicated in Polycomb (Pc) regulation. Therefore, we purified Drosophila Jarid2 and its associated proteins and found that Jarid2 associates with all of the known canonical PRC2 components, demonstrating a conserved physical interaction with PRC2 in flies and mammals. Furthermore, in vivo studies with Jarid2 mutants in flies demonstrate that among several histone modifications tested, only methylation of histone 3 at K27 (H3K27), the mark implemented by PRC2, was affected. Genome-wide profiling of Jarid2, Su(z)12 (Suppressor of zeste 12), and H3K27me3 occupancy by chromatin immunoprecipitation with sequencing (ChIP-seq) indicates that Jarid2 and Su(z)12 have very similar distribution patterns on chromatin. However, Jarid2 and Su(z)12 occupancy levels at some genes are significantly different, with Jarid2 being present at relatively low levels at many Pc response elements (PREs) of certain Homeobox (Hox) genes, providing a rationale for why Jarid2 was never identified in Pc screens. Gene expression analyses show that Jarid2 and E(z) (Enhancer of zeste, a canonical PRC2 component) are not only required for transcriptional repression but might also function in active transcription. Identification of Jarid2 as a conserved PRC2 interactor in flies provides an opportunity to begin to probe some of its novel functions in Drosophila development.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , N-Metiltransferasa de Histona-Lisina/metabolismo , Factores de Transcripción/metabolismo , Transcripción Genética , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Regulación de la Expresión Génica , N-Metiltransferasa de Histona-Lisina/genética , Metilación , Unión Proteica , Factores de Transcripción/genéticaRESUMEN
Methylation of histone H3 lysine 4 (H3K4) in Saccharomyces cerevisiae is implemented by Set1/COMPASS, which was originally purified based on the similarity of yeast Set1 to human MLL1 and Drosophila melanogaster Trithorax (Trx). While humans have six COMPASS family members, Drosophila possesses a representative of the three subclasses within COMPASS-like complexes: dSet1 (human SET1A/SET1B), Trx (human MLL1/2), and Trr (human MLL3/4). Here, we report the biochemical purification and molecular characterization of the Drosophila COMPASS family. We observed a one-to-one similarity in subunit composition with their mammalian counterparts, with the exception of LPT (lost plant homeodomains [PHDs] of Trr), which copurifies with the Trr complex. LPT is a previously uncharacterized protein that is homologous to the multiple PHD fingers found in the N-terminal regions of mammalian MLL3/4 but not Drosophila Trr, indicating that Trr and LPT constitute a split gene of an MLL3/4 ancestor. Our study demonstrates that all three complexes in Drosophila are H3K4 methyltransferases; however, dSet1/COMPASS is the major monoubiquitination-dependent H3K4 di- and trimethylase in Drosophila. Taken together, this study provides a springboard for the functional dissection of the COMPASS family members and their role in the regulation of histone H3K4 methylation throughout development in Drosophila.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , N-Metiltransferasa de Histona-Lisina/metabolismo , Animales , Animales Modificados Genéticamente , Secuencia de Bases , Cartilla de ADN/genética , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Genes de Insecto , Histona Metiltransferasas , N-Metiltransferasa de Histona-Lisina/química , N-Metiltransferasa de Histona-Lisina/genética , Humanos , Metilación , Subunidades de Proteína , Interferencia de ARN , Proteínas de Saccharomyces cerevisiae/química , Especificidad de la EspecieRESUMEN
Polycomb group proteins (PcG) are required for proper developmental regulation and cell fate commitment in metazoans. Recently, four studies reported the identification of JARID2, a JmjC domain-containing protein, as a component of the Polycomb-repressive complex 2 (PRC2), which is involved in implementing histone H3 Lys 27 methylation and transcriptional repression during development. Here, we discuss the implications of these studies for an improved understanding of PcG function in development.
Asunto(s)
Regulación de la Expresión Génica , Silenciador del Gen , N-Metiltransferasa de Histona-Lisina/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Animales , Proteínas de Drosophila/metabolismo , Humanos , RatonesRESUMEN
Epigenetic modifications of chromatin play an important role in the regulation of gene expression. KMT4/Dot1 is a conserved histone methyltransferase capable of methylating chromatin on Lys79 of histone H3 (H3K79). Here we report the identification of a multisubunit Dot1 complex (DotCom), which includes several of the mixed lineage leukemia (MLL) partners in leukemia such as ENL, AF9/MLLT3, AF17/MLLT6, and AF10/MLLT10, as well as the known Wnt pathway modifiers TRRAP, Skp1, and beta-catenin. We demonstrated that the human DotCom is indeed capable of trimethylating H3K79 and, given the association of beta-catenin, Skp1, and TRRAP, we investigated, and found, a role for Dot1 in Wnt/Wingless signaling in an in vivo model system. Knockdown of Dot1 in Drosophila results in decreased expression of a subset of Wingless target genes. Furthermore, the loss of expression for the Drosophila homologs of the Dot1-associated proteins involved in the regulation of H3K79 shows a similar reduction in expression of these Wingless targets. From yeast to human, specific trimethylation of H3K79 by Dot1 requires the monoubiquitination of histone H2B by the Rad6/Bre1 complex. Here, we demonstrate that depletion of Bre1, the E3 ligase required for H2B monoubiquitination, leads specifically to reduced bulk H3K79 trimethylation levels and a reduction in expression of many Wingless targets. Overall, our study describes for the first time the components of DotCom and links the specific regulation of H3K79 trimethylation by Dot1 and its associated factors to the Wnt/Wingless signaling pathway.
Asunto(s)
Histonas/metabolismo , Metiltransferasas/metabolismo , Transducción de Señal , Proteínas Wnt/metabolismo , Animales , Línea Celular , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Regulación Enzimológica de la Expresión Génica , Técnicas de Silenciamiento del Gen , Células HeLa , N-Metiltransferasa de Histona-Lisina , Humanos , Metilación , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMEN
Trimethylated lysine 27 of histone H3 (H3K27me3) is an epigenetic mark for gene silencing and can be demethylated by the JmjC domain of UTX. Excessive H3K27me3 levels can cause tumorigenesis, but little is known about the mechanisms leading to those cancers. Mutants of the Drosophila H3K27me3 demethylase dUTX display some characteristics of Trithorax group mutants and have increased H3K27me3 levels in vivo. Surprisingly, dUTX mutations also affect H3K4me1 levels in a JmjC-independent manner. We show that a disruption of the JmjC domain of dUTX results in a growth advantage for mutant cells over adjacent wild-type tissue due to increased proliferation. The growth advantage of dUTX mutant tissue is caused, at least in part, by increased Notch activity, demonstrating that dUTX is a Notch antagonist. Furthermore, the inactivation of Retinoblastoma (Rbf in Drosophila) contributes to the growth advantage of dUTX mutant tissue. The excessive activation of Notch in dUTX mutant cells leads to tumor-like growth in an Rbf-dependent manner. In summary, these data suggest that dUTX is a suppressor of Notch- and Rbf-dependent tumors in Drosophila melanogaster and may provide a model for UTX-dependent tumorigenesis in humans.