title: Structural and functional analysis of the differential effects of c-Jun and v-Jun on prolactin gene expression.
abstract: The protooncogene c-Jun and its oncogenic isoform v-Jun are members of the activator protein 1 family of transcription factors that have been shown to have differential transcriptional effects that are both promoter specific and cell type specific. Previously, we have demonstrated that whereas c-Jun inhibits pituitary-specific rat prolactin (rPRL) promoter activity, expression of v-Jun stimulates the rPRL promoter in GH4 pituitary cells. In this report, we have conducted an extensive structure-function analysis of c-Jun vs. v-Jun to determine which regions of these proteins are responsible for their differential transcriptional effects in this pituitary model system. We show that isoform-specific responses are mediated by complex interactions between the delta-domain, serine 243, and the amino-terminal transcriptional activation domains. Thus, in contrast to previous reports, no single domain is responsible for the differential transcriptional activities of c-Jun and v-Jun. Mutation of c-Jun serine 243 to phenylalanine and replacement of the c-Jun amino terminus with the corresponding region from v-Jun, thereby removing the delta-domain, are necessary and sufficient to confer a functional switch from the c-Jun-inhibitory to the v-Jun-activating phenotype. Thus, we propose that isoform-specific subdomains in c-Jun and v-Jun dictate discrete interactions with distinct protein partners, which underlie the differential Jun-dependent transcriptional responses of the rPRL promoter.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Aurora 80045, USA.
authors.forename: Kathryn N
authors.initials: KN
authors.lastname: Farrow
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Bradford
authors.forename: John J
authors.initials: JJ
authors.lastname: Tentler
authors.forename: Arthur
authors.initials: A
authors.lastname: Gutierrez-Hartmann
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology*; D005822:Genetic Vectors; D016297:Mutagenesis, Site-Directed; D016759:Oncogene Protein p65(gag-jun) / Q000502:physiology*; D011388:Prolactin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology*; D051381:Rats
chemical_list: D016759:Oncogene Protein p65(gag-jun); D016755:Proto-Oncogene Proteins c-jun; D011388:Prolactin