title: Forced expression of the interferon regulatory factor 2 oncoprotein causes polyploidy and cell death in FDC-P1 myeloid hematopoietic progenitor cells.
abstract: The IFN regulatory factor-2 (IRF-2) oncoprotein controls the cell cycle-dependent expression of histone H4 genes during S phase and may function as a component of an E2F-independent mechanism to regulate cell growth. To investigate the role of IRF-2 in control of cell proliferation, we have constructed a stable FDC-P1 cell line (F2) in which expression of IRF-2 is doxycycline (DOX)-inducible, and a control cell line (F0). Both the F2 and F0 cell lines were synchronized in the G1 phase by isoleucine deprivation, and IRF-2 was induced by DOX on release of cells from the cell cycle block. Flow cytometric analyses indicated that forced expression of IRF-2 has limited effects on cell cycle progression before the first mitosis. However, continued cell growth in the presence of elevated IRF-2 levels results in polyploidy (>4n) or genomic disintegration (<2n) and cell death. Western blot analyses revealed that the levels of the cell cycle regulatory proteins cyclin B1 and the cyclin-dependent kinase (CDK)-inhibitory protein p27 are selectively increased. These changes occur concomitant with a significant elevation in the levels of the FAS-L protein, which is the ligand of the FAS (Apo1/CD95) receptor. We also found a subtle change in the ratio of the apoptosis-promoting Bax protein and the antiapoptotic Bcl-2 protein. Hence, IRF-2 induces a cell death response involving the Fas/FasL apoptotic pathway in FDC-P1 cells. Our data suggest that the IRF-2 oncoprotein regulates a critical cell cycle checkpoint that controls progression through G2 and mitosis in FDC-P1 hematopoietic progenitor cells.
authors: Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
authors: Rong-Lin
authors: RL
authors: Xie
authors: Andre J
authors: AJ
authors: van Wijnen
authors: Caroline M
authors: CM
authors: van der Meijden
authors: Janet L
authors: JL
authors: Stein
authors: Gary S
authors: GS
authors: Stein
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D053222:Fas Ligand Protein; D016193:G1 Phase / Q000502:physiology; D005786:Gene Expression Regulation; D006657:Histones / Q000096:biosynthesis / Q000235:genetics; D050836:Interferon Regulatory Factor-2; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D023461:Myeloid Progenitor Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011123:Polyploidy; D012097:Repressor Proteins; D016196:S Phase / Q000502:physiology; D014157:Transcription Factors; D015854:Up-Regulation; D019014:fas Receptor / Q000096:biosynthesis
chemical_list: D004268:DNA-Binding Proteins; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D006657:Histones; D050836:Interferon Regulatory Factor-2; C494230:Irf2 protein, mouse; D008562:Membrane Glycoproteins; D012097:Repressor Proteins; D014157:Transcription Factors; D019014:fas Receptor