Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 3 de 3
Filtrar
Mais filtros

Base de dados
Tipo de documento
País de afiliação
Intervalo de ano de publicação
1.
Mol Cell ; 80(4): 726-735.e7, 2020 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-33049227

RESUMO

Diffuse midline gliomas and posterior fossa type A ependymomas contain the recurrent histone H3 lysine 27 (H3 K27M) mutation and express the H3 K27M-mimic EZHIP (CXorf67), respectively. H3 K27M and EZHIP are competitive inhibitors of Polycomb Repressive Complex 2 (PRC2) lysine methyltransferase activity. In vivo, these proteins reduce overall H3 lysine 27 trimethylation (H3K27me3) levels; however, residual peaks of H3K27me3 remain at CpG islands (CGIs) through an unknown mechanism. Here, we report that EZHIP and H3 K27M preferentially interact with PRC2 that is allosterically activated by H3K27me3 at CGIs and impede its spreading. Moreover, H3 K27M oncohistones reduce H3K27me3 in trans, independent of their incorporation into the chromatin. Although EZHIP is not found outside placental mammals, expression of human EZHIP reduces H3K27me3 in Drosophila melanogaster through a conserved mechanism. Our results provide mechanistic insights for the retention of residual H3K27me3 in tumors driven by H3 K27M and EZHIP.


Assuntos
Cromatina/genética , Metilação de DNA , Regulação Neoplásica da Expressão Gênica , Histonas/genética , Mutação , Proteínas Oncogênicas/metabolismo , Complexo Repressor Polycomb 2/metabolismo , Regulação Alostérica , Animais , Ilhas de CpG , Drosophila melanogaster , Humanos , Camundongos , Proteínas Oncogênicas/genética , Complexo Repressor Polycomb 2/genética
2.
Nat Commun ; 10(1): 2146, 2019 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-31086175

RESUMO

Posterior fossa type A (PFA) ependymomas exhibit very low H3K27 methylation and express high levels of EZHIP (Enhancer of Zeste Homologs Inhibitory Protein, also termed CXORF67). Here we find that a conserved sequence in EZHIP is necessary and sufficient to inhibit PRC2 catalytic activity in vitro and in vivo. EZHIP directly contacts the active site of the EZH2 subunit in a mechanism similar to the H3 K27M oncohistone. Furthermore, expression of H3 K27M or EZHIP in cells promotes similar chromatin profiles: loss of broad H3K27me3 domains, but retention of H3K27me3 at CpG islands. We find that H3K27me3-mediated allosteric activation of PRC2 substantially increases the inhibition potential of EZHIP and H3 K27M, providing a mechanism to explain the observed loss of H3K27me3 spreading in tumors. Our data indicate that PFA ependymoma and DIPG are driven in part by the action of peptidyl PRC2 inhibitors, the K27M oncohistone and the EZHIP 'oncohistone-mimic', that dysregulate gene silencing to promote tumorigenesis.


Assuntos
Neoplasias Encefálicas/genética , Ependimoma/genética , Glioma/genética , Proteínas Oncogênicas/metabolismo , Complexo Repressor Polycomb 2/metabolismo , Animais , Neoplasias Encefálicas/patologia , Carcinogênese/genética , Linhagem Celular Tumoral , Cromatina/metabolismo , Ilhas de CpG , Fossa Craniana Posterior , Conjuntos de Dados como Assunto , Embrião de Mamíferos , Ependimoma/patologia , Fibroblastos , Regulação Neoplásica da Expressão Gênica , Inativação Gênica , Glioma/patologia , Células HEK293 , Histonas , Humanos , Camundongos , Proteínas Oncogênicas/genética , Cultura Primária de Células , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo
3.
mBio ; 6(1): e02357-14, 2015 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-25691595

RESUMO

UNLABELLED: The inner membrane complex (IMC) of Toxoplasma gondii is a peripheral membrane system that is composed of flattened alveolar sacs that underlie the plasma membrane, coupled to a supporting cytoskeletal network. The IMC plays important roles in parasite replication, motility, and host cell invasion. Despite these central roles in the biology of the parasite, the proteins that constitute the IMC are largely unknown. In this study, we have adapted a technique named proximity-dependent biotin identification (BioID) for use in T. gondii to identify novel components of the IMC. Using IMC proteins in both the alveoli and the cytoskeletal network as bait, we have uncovered a total of 19 new IMC proteins in both of these suborganellar compartments, two of which we functionally evaluate by gene knockout. Importantly, labeling of IMC proteins using this approach has revealed a group of proteins that localize to the sutures of the alveolar sacs that have been seen in their entirety in Toxoplasma species only by freeze fracture electron microscopy. Collectively, our study greatly expands the repertoire of known proteins in the IMC and experimentally validates BioID as a strategy for discovering novel constituents of specific cellular compartments of T. gondii. IMPORTANCE: The identification of binding partners is critical for determining protein function within cellular compartments. However, discovery of protein-protein interactions within membrane or cytoskeletal compartments is challenging, particularly for transient or unstable interactions that are often disrupted by experimental manipulation of these compartments. To circumvent these problems, we adapted an in vivo biotinylation technique called BioID for Toxoplasma species to identify binding partners and proximal proteins within native cellular environments. We used BioID to identify 19 novel proteins in the parasite IMC, an organelle consisting of fused membrane sacs and an underlying cytoskeleton, whose protein composition is largely unknown. We also demonstrate the power of BioID for targeted discovery of proteins within specific compartments, such as the IMC cytoskeleton. In addition, we uncovered a new group of proteins localizing to the alveolar sutures of the IMC. BioID promises to reveal new insights on protein constituents and interactions within cellular compartments of Toxoplasma.


Assuntos
Membrana Celular/química , Parasitologia/métodos , Proteoma/análise , Proteínas de Protozoários/análise , Coloração e Rotulagem/métodos , Toxoplasma/química , Técnicas de Química Analítica/métodos , Técnicas Citológicas/métodos , Técnicas de Inativação de Genes , Toxoplasma/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA