title: CCAAT/enhancer-binding protein delta regulates mammary epithelial cell G0 growth arrest and apoptosis.
abstract: CCAAT/enhancer-binding proteins (C/EBPs) are a highly conserved family of DNA-binding proteins that regulate cell-specific growth, differentiation, and apoptosis. Here, we show that induction of C/EBPdelta gene expression during G0 growth arrest is a general property of mammary-derived cell lines. C/EBPdelta is not induced during G0 growth arrest in 3T3 or IEC18 cells. C/EBPdelta induction is G0-specific in mouse mammary epithelial cells; C/EBPdelta gene expression is not induced by growth arrest in the G1, S, or G2 phase of the cell cycle. C/EBPdelta antisense-expressing cells (AS1 cells) maintain elevated cyclin D1 and phosphorylated retinoblastoma protein levels and exhibit delayed G0 growth arrest and apoptosis in response to serum and growth factor withdrawal. Conversely, C/EBPdelta-overexpressing cells exhibited a rapid decline in cyclin D1 and phosphorylated retinoblastoma protein levels, a rapid increase in the cyclin-dependent kinase inhibitor p27, and accelerated G0 growth arrest and apoptosis in response to serum and growth factor withdrawal. When C/EBPdelta levels were rescued in AS1 cells by transfection with a C/EBPdelta "sense" construct, normal G0 growth arrest and apoptosis were restored. These results demonstrate that C/EBPdelta plays a key role in the regulation of G0 growth arrest and apoptosis in mammary epithelial cells.
authors.affiliation: Department of Veterinary Biosciences, Ohio State Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: O'Rourke
authors.forename: G C
authors.initials: GC
authors.lastname: Newbound
authors.forename: J A
authors.initials: JA
authors.lastname: Hutt
authors.forename: J
authors.initials: J
authors.lastname: DeWille
mesh_terms: D000818:Animals; D017209:Apoptosis; D022762:CCAAT-Enhancer-Binding Proteins; D002455:Cell Division; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D004847:Epithelial Cells / Q000166:cytology*; D005260:Female; D008321:Mammary Glands, Animal / Q000166:cytology*; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D016192:Resting Phase, Cell Cycle; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D014157:Transcription Factors