RESUMO
In papillary renal cell carcinomas the TFE3 transcription factor becomes fused to the PSF and NonO pre-mRNA splicing factors and most commonly to a protein of unknown function designated PRCC. In this study we have examined the ability of the resulting PRCC-TFE3 and NonO-TFE3 fusions to activate transcription from the plasminogen activator inhibitor-1 (PAI-1) promoter. The results show that only fusion to PRCC enhanced transcriptional activation, indicating that the ability to enhance the level of transcription from endogenous TFE3 promoters is not a consistent feature of TFE3 fusions. In investigations of the normal function of PRCC we observed that PRCC expressed as a green fluorescent fusion protein colocalizes within the nucleus with Sm pre-mRNA splicing factors. It was also found that endogenous PRCC is coimmunoprecipitated by antibodies that recognize a variety of pre-mRNA splicing factors including SC35, PRL1 and CDC5. Association with the cellular splicing machinery is therefore, a common feature of the proteins that become fused to TFE3 in papillary renal cell carcinomas.
Assuntos
Carcinoma de Células Renais/genética , Proteínas de Ciclo Celular , Proteínas de Ligação a DNA/genética , Neoplasias Renais/genética , Proteínas Luminescentes , Proteínas de Neoplasias , Proteínas Nucleares/metabolismo , Proteínas/genética , Ribonucleoproteínas , Proteínas de Saccharomyces cerevisiae , Fatores de Transcrição/genética , Adulto , Amanitinas/farmacologia , Animais , Fusão Gênica Artificial , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Carcinoma Papilar/tratamento farmacológico , Carcinoma Papilar/genética , Carcinoma Papilar/metabolismo , Carcinoma de Células Renais/tratamento farmacológico , Carcinoma de Células Renais/metabolismo , Proteínas de Ligação a DNA/metabolismo , Inibidores Enzimáticos/farmacologia , Feminino , Proteínas de Fluorescência Verde , Humanos , Neoplasias Renais/tratamento farmacológico , Neoplasias Renais/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Masculino , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases , Proteínas/metabolismo , Precursores de RNA/genética , Splicing de RNA , RNA Mensageiro/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Ribonucleoproteínas Nucleares Pequenas/metabolismo , Fatores de Processamento de Serina-Arginina , Fatores de Transcrição/metabolismo , Transcrição Gênica , Células Tumorais CultivadasRESUMO
MGA2 and SPT23 are functionally and genetically redundant homologs in Saccharomyces cerevisiae. Both genes are implicated in the transcription of a subset of genes, including Ty retrotransposons and Ty-induced mutations. Neither gene is essential for growth, but mga2 spt23 double mutants are inviable. We have isolated a gene-specific activator, SWI5, and the Delta9 fatty acid desaturase of yeast, OLE1, as multicopy suppressors of an mga2Delta spt23 temperature-sensitive mutation (spt23-ts). The level of unsaturated fatty acids decreases 35-40% when the mga2Delta spt23-ts mutant is incubated at 37 degrees. Electron microscopy of these cells reveals a separation of inner and outer nuclear membranes that is sometimes accompanied by vesicle-like projections in the intermembrane space. The products of Ole1p catalysis, oleic acid and palmitoleic acid, suppress mga2Delta spt23-ts and mga2Delta spt23Delta lethality and restore normal nuclear membrane morphology. Furthermore, the level of the OLE1 transcript decreases more than 15-fold in the absence of wild-type Mga2p and Spt23p. Our results suggest that Mga2p/Spt23p control cell viability by stimulating OLE1 transcription.