RESUMO
The human oncogene JUN encodes a component of the AP-1 complex and is consequently involved in a wide range of pivotal cellular processes, including cell proliferation, transformation, and apoptosis. Nevertheless, despite extensive analyses of its functions, it has never been directly involved in a human cancer. We demonstrate here that it is highly amplified and overexpressed in undifferentiated and aggressive human sarcomas, which are blocked at an early step of adipocyte differentiation. We confirm by cellular and xenograft mouse models recapitulating these sarcoma genetics that the failure to differentiate is dependent upon JUN amplification/overexpression.
Assuntos
Adipócitos/patologia , Diferenciação Celular , Amplificação de Genes , Lipossarcoma/patologia , Proteínas Proto-Oncogênicas c-jun/genética , Células 3T3-L1 , Adipócitos/metabolismo , Adipogenia , Idoso , Animais , Cromossomos Artificiais Bacterianos , Cromossomos Humanos Par 1/genética , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Humanos , Lipossarcoma/genética , Lipossarcoma/metabolismo , Camundongos , Camundongos Nus , Proteínas Proto-Oncogênicas c-jun/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Neoplasias Retroperitoneais/genética , Neoplasias Retroperitoneais/metabolismo , Neoplasias Retroperitoneais/patologia , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Protein kinases orthologous with Cak1 of Saccharomyces cerevisiae (ScCak1) appear specific to ascomycetes. ScCak1 phosphorylates Cdc28, the cyclin-dependent kinase (CDK) governing the cell cycle, as well as Kin28, Bur1 and Ctk1, CDKs required for the transcription process performed by RNA polymerase II (RNA Pol II). Using genetic methods, we found that Cak1 genetically interacts with Paf1 and Ctr9, two components belonging to the PAF1 elongation complex needed for histone modifications, and with Ssu72, a protein phosphatase that dephosphorylates serine-5 phosphate in the RNA Pol II C-terminal domain. We present evidence suggesting that the interactions linking Cak1 with the PAF1 complex and with Ssu72 are not direct but mediated via Ctk1 and Bur1. We discuss the possibility that Ssu72 intervenes at the capping checkpoint step of the transcription cycle.
Assuntos
Proteínas de Transporte/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Quinases/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Sequência de Bases , Proteínas de Transporte/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Quinases Ciclina-Dependentes/genética , DNA Complementar/genética , DNA Fúngico/genética , Genes Fúngicos , Genes Letais , Mutação , Proteínas Nucleares/genética , Fosfoproteínas Fosfatases , Plasmídeos/genética , Proteínas Quinases/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Supressão Genética , Temperatura , Fatores de Elongação da Transcrição , Fatores de Poliadenilação e Clivagem de mRNA , Quinase Ativadora de Quinase Dependente de CiclinaRESUMO
Ssu72 is an essential yeast protein that is involved in transcription. It physically interacts with transcription initiation and termination complexes. In this report, we provide evidence that Ssu72 is a phosphatase that physically interacts with the CTD kinase Kin28 and functionally interacts with the CTD phosphatase Fcp1. A genome-wide expression analysis of mutant ssu72-ts69 during growth in complete medium revealed a number of defects, including the accumulation of a limited number of mRNAs and the read-through transcription of small nucleolar RNAs and of some mRNAs. We hypothesize that Ssu72 plays a key role in the transcription termination of certain transcripts, possibly by promoting RNA polymerase pausing and release. The possibility that the CTD of the largest subunit of RNA polymerase II is a substrate of Ssu72 is discussed.