The COUP-adjacent repressor (CAR) element participates in the tissue-specific expression of the ovalbumin gene.
The ovalbumin (Ov) gene is an excellent model for the study of tissue-specific gene regulation as it is only active in the estrogen-stimulated oviduct. Previous studies have demonstrated that the negative regulatory element (NRE) in the Ov gene 5'-flanking region is responsible for silencing the gene in oviduct in the absence of steroids. Linker scanning analysis defined an element within the NRE designated the COUP-adjacent repressor (CAR) element as a repressor of Ov gene expression. However, the role of the CAR element in non-oviduct tissues has not been addressed. Using transient transfection analysis of various Ov 5'-flanking region constructs into the estrogen-responsive chicken hepatocyte cell line LMH/2A, we demonstrate that Ov gene expression is not induced by estrogen and that an active repressor element exists in the NRE. Deletion analysis indicates that the region from -134 to -87, which includes the CAR element, mediates this repression. Mutation of the CAR element relieves repression, leading to high levels of gene expression. These data support a model where the inhibition of Ov gene expression in non-oviduct cells is a combination of the lack of essential positive factors and the presence of an active repressor, which binds to the CAR element.
Monroe
D G
DG
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455, USA.
Sanders
M M
MM
D000818:Animals; D051836:COUP Transcription Factors; D002460:Cell Line; D002645:Chickens; D004268:DNA-Binding Proteins / Q000235:genetics*; D004967:Estrogens; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D009154:Mutation; D010047:Ovalbumin / Q000235:genetics*; D011987:Receptors, Steroid; D012097:Repressor Proteins / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins; D004967:Estrogens; D011987:Receptors, Steroid; D012097:Repressor Proteins; D014157:Transcription Factors; D010047:Ovalbumin