title: Oncogenic fusion protein EWS/FLI1 down-regulates gene expression by both transcriptional and posttranscriptional mechanisms.
abstract: Ewing family tumors are characterized by a translocation between the RNA binding protein EWS and one of five ETS transcription factors, most commonly FLI1. The fusion protein produced by the translocation has been thought to act as an aberrant transcription factor, leading to changes in gene expression and cellular transformation. In this study, we investigated the specific processes EWS/FLI1 utilizes to alter gene expression. Using both heterologous NIH 3T3 and human Ewing Family Tumor cell lines, we have demonstrated by quantitative pre-mRNA analysis that EWS/FLI1 repressed the expression of previously validated direct target genes at the level of transcript synthesis. ChIP experiments showed that EWS/FLI1 decreases the amount of Pol II at the promoter of down-regulated genes in both murine and human model systems. However, in down-regulated target genes, there was a significant disparity between the modulation of cognate mRNA and pre-mRNAs, suggesting that these genes could also be regulated at a posttranscriptional level. Confirming this, we found that EWS/FLI1 decreased the transcript half-life of insulin-like growth factor binding protein 3, a down-regulated direct target gene in human tumor-derived Ewing's sarcoma cell lines. Additionally, we have shown through reexpression experiments that full EWS/FLI1-mediated transcriptional repression requires intact EWS and ETS domains. Together these data demonstrate that EWS/FLI1 can dictate steady-state target gene expression by modulating both transcript synthesis and degradation.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: France
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Anderson
authors.forename: Ann
authors.initials: A
authors.lastname: Park
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Denny
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D015514:Oncogene Proteins, Fusion / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D051789:Proto-Oncogene Protein c-fli-1 / Q000096:biosynthesis* / Q000235:genetics; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012322:RNA Precursors / Q000096:biosynthesis* / Q000235:genetics; D020871:RNA Stability; D034802:RNA-Binding Protein EWS / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; C106031:EWS-FLI fusion protein; C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D012322:RNA Precursors; D034802:RNA-Binding Protein EWS; D012319:RNA Polymerase II