Regulation of CEACAM1 transcription in human breast epithelial cells.
BACKGROUND
Carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is a transmembrane protein with multiple functions in different cell types. CEACAM1 expression is frequently mis-regulated in cancer, with down-regulation reported in several tumors of epithelial origin and de novo expression of CEACAM1 in lung cancer and malignant melanoma. In this report we analyzed the regulation of CEACAM1 expression in three breast cancer cell lines that varied in CEACAM1 expression from none (MCF7) to moderate (MDA-MB-468) to high (MCF10A, comparable to normal breast).


RESULTS
Using in vivo footprinting and chromatin immunoprecipitation experiments we show that the CEACAM1 proximal promoter in breast cells is bound in its active state by SP1, USF1/USF2, and IRF1/2. When down-regulated the CEACAM1 promoter remains accessible to USF2 and partially accessible to USF1. Interferon-γ up-regulates CEACAM1 mRNA by a mechanism involving further induction of IRF-1 and USF1 binding at the promoter. As predicted by this analysis, silencing of IRF1 and USF1 but not USF2 by RNAi resulted in a significant decrease in CEACAM1 protein expression in MDA-MB-468 cells. The inactive CEACAM1 promoter in MCF7 cells exhibits decreased histone acetylation at the promoter region, with no evidence of H3K9 or H3K27 trimethylation, histone modifications often linked to condensed chromatin structure.


CONCLUSIONS
Our data suggest that transcription activators USF1 and IRF1 interact to modulate CEACAM1 expression and that the chromatin structure of the promoter is likely maintained in a poised state that can promote rapid induction under appropriate conditions.
Department of Immunology, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA.
Marieta
M
Gencheva
Charng-Jui
CJ
Chen
Tung
T
Nguyen
John E
JE
Shively
D015703:Antigens, CD / Q000235:genetics*; D001940:Breast / Q000166:cytology*; D015815:Cell Adhesion Molecules / Q000235:genetics*; D002460:Cell Line; D002843:Chromatin / Q000737:chemistry; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000378:metabolism; D050836:Interferon Regulatory Factor-2 / Q000235:genetics / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D015533:Transcriptional Activation; D051720:Upstream Stimulatory Factors / Q000235:genetics / Q000378:metabolism
D015703:Antigens, CD; C069847:CD66 antigens; D015815:Cell Adhesion Molecules; D002843:Chromatin; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D012333:RNA, Messenger; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors; D007371:Interferon-gamma