C/EBPdelta is a crucial regulator of pro-apoptotic gene expression during mammary gland involution.
The STAT3 transcription factor is an important initiator of mammary gland involution in the mouse. This work shows that the STAT3 target gene CCAAT/enhancer binding protein delta (C/EBPdelta) is a crucial mediator of pro-apoptotic gene expression events in mammary epithelial cells. In the absence of C/EBPdelta, involution is delayed, the pro-apoptotic genes encoding p53, BAK, IGFBP5 and SGP2/clusterin are not activated, while the anti-apoptotic genes coding for BFL1 and Cyclin D1 are not repressed. Consequently, p53 targets such as survivin, BRCA1, BRCA2 and BAX are not regulated appropriately and protease activation is delayed. Furthermore, expression of MMP3 and C/EBPdelta during the second phase of involution is perturbed in the absence of C/EBPdelta. In HC11 cells, C/EBPdelta alone is sufficient to induce IGFBP5 and SGP2. It also suppresses Cyclin D1 expression and cooperates with p53 to elicit apoptosis. This study places C/EBPdelta between STAT3 and several pro- and anti-apoptotic genes promoting the physiological cell death response in epithelial cells at the onset of mammary gland involution.
Thangaraju
Muthusamy
M
Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
Rudelius
Martina
M
Bierie
Brian
B
Raffeld
Mark
M
Sharan
Shikha
S
Hennighausen
Lothar
L
Huang
A-Mei
AM
Sterneck
Esta
E
D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000502:physiology*; D051152:Clusterin / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000235:genetics; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008817:Mice, Mutant Strains; D009024:Morphogenesis / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
D051152:Clusterin; D018975:Insulin-Like Growth Factor Binding Protein 5; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D016159:Tumor Suppressor Protein p53; D019938:Cyclin D1; D051743:CCAAT-Enhancer-Binding Protein-delta