CELLULAR REGULATION BY HOMOLOGOUS ONCOPROTEINS

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The overall aims of this proposal are to gain insight into the mechanisms involved in differential expression of two closely related proto-oncogene products, cJun and Jun B. One of the working models for oncogenesis is that of the imbalanced expression between the dominant acting and dominant negative genes, c-jun and jun B, leading to increased transcription of a set of genes which can provide the malignant phenotype. To achieve the overall aims of this proposal, our immediate goal is to further our understanding of the activation of cellular factor(s) which mediate the induction of jun B gene expression. The identification of cis-elements and cellular factors that mediate induction of jun B expression by stimuli will help us to understand the differential behavior of this protein, Jun B, from cJun. The specific objectives of this proposal are: 1.) To define cis-acting elements in the jun B 5'-regulatory region involved in enhanced expression of the jun B gene by TPA and forskolin. 2.) To isolate and characterize trans-acting factor(s) that bind to the defined cis-acting element in the jun B 5'- regulatory region. 3.) To generate antisera against transactivator produced by a bacterially expressed cDNA clone and use it to elucidate the biochemical mechanisms. 4.) To determine the molecular. events leading to the activation of a newly identified transactivator by inducers that regulate jun B gene expression. These objectives can be accomplished by transfection, CAT assays, footprint analysis, gel retardation, protein purification, library screening, cell-free transcription-translation i systems, and immunoprecipitation. It is expected that in-depth investigation of jun B gene expression will lead to a better understanding of the identity and function of Jun B in negatively regulating c-jun expression. Therefore accomplishment of these goals should extend our knowledge of cellular regulation by homologous oncoproteins.