RESUMO
Recently, we reported that the histone methyltransferase, EZH2, controls leukocyte migration through interaction with the cytoskeleton remodeling effector, VAV, and direct methylation of the cytoskeletal regulatory protein, Talin. However, it is unclear whether this extranuclear, epigenetic-independent function of EZH2 has a profound impact on the initiation of cellular transformation and metastasis. Here, we show that EZH2 increases Talin1 methylation and cleavage, thereby enhancing adhesion turnover and promoting accelerated tumorigenesis. This transforming capacity is abolished by targeted disruption of EZH2 interaction with VAV. Furthermore, our studies demonstrate that EZH2 in the cytoplasm is closely associated with cancer stem cell properties, and that overexpression of EZH2, a mutant EZH2 lacking its nuclear localization signal (EZH2ΔNLS), or a methyl-mimicking Talin1 mutant substantially promotes JAK2-dependent STAT3 activation and cellular transformation. Taken together, our results suggest a critical role for the VAV interaction-dependent, extranuclear action of EZH2 in neoplastic transformation.
Assuntos
Transformação Celular Neoplásica/genética , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Regulação Neoplásica da Expressão Gênica , Neoplasias/patologia , Proteínas Proto-Oncogênicas c-vav/metabolismo , Animais , Adesão Celular/genética , Linhagem Celular Tumoral , Transformação Celular Neoplásica/patologia , Citoplasma/genética , Citoplasma/patologia , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Proteína Potenciadora do Homólogo 2 de Zeste/isolamento & purificação , Feminino , Técnicas de Silenciamento de Genes , Células HEK293 , Humanos , Janus Quinase 2/genética , Janus Quinase 2/metabolismo , Células Jurkat , Metilação , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos NOD , Camundongos SCID , Mutagênese Sítio-Dirigida , Neoplasias/genética , Sinais de Localização Nuclear/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/metabolismo , Talina/genética , Talina/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
X-linked intellectual disability (XLID) is a clinically and genetically heterogeneous disorder. During the past two decades in excess of 100 X-chromosome ID genes have been identified. Yet, a large number of families mapping to the X-chromosome remained unresolved suggesting that more XLID genes or loci are yet to be identified. Here, we have investigated 405 unresolved families with XLID. We employed massively parallel sequencing of all X-chromosome exons in the index males. The majority of these males were previously tested negative for copy number variations and for mutations in a subset of known XLID genes by Sanger sequencing. In total, 745 X-chromosomal genes were screened. After stringent filtering, a total of 1297 non-recurrent exonic variants remained for prioritization. Co-segregation analysis of potential clinically relevant changes revealed that 80 families (20%) carried pathogenic variants in established XLID genes. In 19 families, we detected likely causative protein truncating and missense variants in 7 novel and validated XLID genes (CLCN4, CNKSR2, FRMPD4, KLHL15, LAS1L, RLIM and USP27X) and potentially deleterious variants in 2 novel candidate XLID genes (CDK16 and TAF1). We show that the CLCN4 and CNKSR2 variants impair protein functions as indicated by electrophysiological studies and altered differentiation of cultured primary neurons from Clcn4(-/-) mice or after mRNA knock-down. The newly identified and candidate XLID proteins belong to pathways and networks with established roles in cognitive function and intellectual disability in particular. We suggest that systematic sequencing of all X-chromosomal genes in a cohort of patients with genetic evidence for X-chromosome locus involvement may resolve up to 58% of Fragile X-negative cases.