Little is known about the control of cell cycle exit/G(0) entry, or the regulation of genes that are expressed during G(0). In this report we used primer extension analysis to demonstrate the high level of C/EBPdelta mRNA expression in G(0) growth-arrested HC11 mouse mammary epithelial cells and to identify the C/EBPdelta transcription start site. The C/EBPdelta gene transcription rate and promoter activity are both highly induced in G(0) growth-arrested HC11 cells. The C/EBPdelta gene promoter also exhibits G(0)-specific autoregulation. In contrast, the C/EBPdelta promoter activity decreases in G(0) growth-arrested NIH 3T3 cells. These data indicate that C/EBPdelta is among a relatively small number of genes actively transcribed during G(0) growth arrest. C/EBPdelta may regulate the expression of genes implicated in the initiation or maintenance of mammary epithelial cell G(0) growth arrest.
Copyright 1999 Academic Press.