The inhibitory activity of a transdominant c-jun mutant fused to the ligand binding domain of the estrogen receptor.
Tam-67 is an amino-terminal deletion mutant of c-Jun (delta3-122) lacking most of the c-Jun transactivation domain, which has been shown previously to function in a transdominant fashion to inhibit c-Jun-induced transactivation and cellular transformation. In order to create a ligand-dependent dominant negative repressor of AP-1, we have constructed a fusion of the TAM-67 gene with the ligand binding domain of the estrogen receptor. Fusion of TAM-67 with the ligand binding domain of the estrogen receptor produced a 68 kD protein (TAM-67ER) which was immunoprecipitated by c-Jun-specific and estrogen receptor-specific antisera and shown by gel retardation assay to bind oligonucleotides containing an AP-1 sequence. Cotransfection of TAM-67ER and an AP-1-dependent reporter construct into rat embryo cells demonstrated ligand specific inhibition of AP-1 transactivation. In the absence of hormone, TAM-67ER produced complete inhibition of c-Jun-induced AP-I transactivation. This inhibition was relieved by treatment with estradiol but not by treatment with tamoxifen. In addition, TAM-67ER inhibited activated c-Ha-ras- or c-raf-induced transformation of NIH3T3 cells. However, this inhibition of transformation was not relieved by the addition of estrogen. Thus, TAM-67ER inhibits transactivation in a ligand-dependent manner, but inhibits transformation in a ligand-independent manner. The results suggest that the ligand-dependent transactivation domain of the estrogen receptor (TAF-2) can substitute for the c-Jun transactivation domain absent in TAM-67 to stimulate transactivation. However, TAF-2 cannot substitute for the missing c-Jun transactivation domain to induce cellular transformation.
Kim
S
S
Biomarkers and Prevention Research Branch, Division of Clinical Sciences, National Cancer Institute, Rockville, Maryland 20850, USA.
Brown
P H
PH
Birrer
M J
MJ
D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects; D005822:Genetic Vectors; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011960:Receptors, Estrogen / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology; D013696:Temperature; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*
D004965:Estrogen Antagonists; D008024:Ligands; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D013629:Tamoxifen; D004958:Estradiol; D004247:DNA