title: Context-dependent requirement for dE2F during oncogenic proliferation.
abstract: The Hippo pathway negatively regulates the cell number in epithelial tissue. Upon its inactivation, an excess of cells is produced. These additional cells are generated from an increased rate of cell division, followed by inappropriate proliferation of cells that have failed to exit the cell cycle. We analyzed the consequence of inactivation of the entire E2F family of transcription factors in these two settings. In Drosophila, there is a single activator, dE2F1, and a single repressor, dE2F2, which act antagonistically to each other during development. While the loss of the activator dE2F1 results in a severe impairment in cell proliferation, this defect is rescued by the simultaneous loss of the repressor dE2F2, as cell proliferation occurs relatively normally in the absence of both dE2F proteins. We found that the combined inactivation of dE2F1 and dE2F2 had no significant effect on the increased rate of cell division of Hippo pathway mutant cells. In striking contrast, inappropriate proliferation of cells that failed to exit the cell cycle was efficiently blocked. Furthermore, our data suggest that such inappropriate proliferation was primarily dependent on the activator, de2f1, as loss of de2f2 was inconsequential. Consistently, Hippo pathway mutant cells had elevated E2F activity and induced dE2F1 expression at a point when wild-type cells normally exit the cell cycle. Thus, we uncovered a critical requirement for the dE2F family during inappropriate proliferation of Hippo pathway mutant cells.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Illinois, United States of America.
authors.forename: Brandon N
authors.initials: BN
authors.lastname: Nicolay
authors.forename: Maxim V
authors.initials: MV
authors.lastname: Frolov
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D050703:E2F2 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D005123:Eye / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014921:Wings, Animal / Q000254:growth & development / Q000378:metabolism; D000091102:YAP-Signaling Proteins; D000099317:Hippo Kinases
chemical_list: D029721:Drosophila Proteins; D050703:E2F2 Transcription Factor; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D000091102:YAP-Signaling Proteins; C496298:E2f1 protein, Drosophila; C115434:E2f2 protein, Drosophila; C503814:Yki protein, Drosophila; C499474:hpo protein, Drosophila; D000099317:Hippo Kinases