Posttranscriptional and posttranslational regulation of C/EBP delta in G0 growth-arrested mammary epithelial cells.
Previous work from our laboratory demonstrated that CCAAT/enhancer-binding protein delta (C/EBP delta) functions in the initiation and maintenance of G(0) growth arrest in mouse mammary epithelial cells (MECs). In this report, we investigated the posttranscriptional and posttranslational regulation of C/EBP delta in G(0) growth-arrested mouse MECs. The results of transcriptional inhibitor studies demonstrated that the C/EBP delta mRNA exhibits a relatively short half-life in G(0) growth-arrested mouse MECs (t(1/2) approximately 35 min). In contrast, C/EBP delta mRNA has a longer half-life in G(0) growth-arrested mouse fibroblast cells (t(1/2) >100 min). Oligo/RNase H cleavage analysis and rapid amplification of cDNA ends-poly(A) test both confirmed the short C/EBP delta mRNA half-life observed in MECs and demonstrated that the C/EBP delta mRNA poly(A) tail is relatively short (approximately 100 nucleotides). In addition, the poly(A) tail length was not shortened during C/EBP delta mRNA degradation, which suggested a deadenylation-independent pathway. The C/EBP delta protein also exhibited a relatively short half-life in G(0) growth-arrested mouse MECs (t(1/2) approximately 120 min). The C/EBP delta protein was degraded in a ubiquitin-dependent manner, primarily in the nucleus, during G(0) growth arrest. In conclusion, these studies indicated that the C/EBP delta mRNA and protein content are under tight regulation in G(0) growth-arrested mouse MECs, despite the general concept that G(0) growth arrest is associated with a decrease in cellular activity.
Dearth
Lawrence R
LR
Molecular, Cellular, and Developmental Biology Graduate Program, the Ohio State University, Columbus, Ohio 43210-1093, USA.
DeWille
James
J
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D017931:DNA Primers; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D011499:Protein Processing, Post-Translational; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics; D016192:Resting Phase, Cell Cycle / Q000502:physiology*; D014157:Transcription Factors
D022762:CCAAT-Enhancer-Binding Proteins; C497253:Cebpd protein, mouse; D017931:DNA Primers; D012333:RNA, Messenger; D014157:Transcription Factors; D051743:CCAAT-Enhancer-Binding Protein-delta