Structure-Function Analysis of the v-Myc Oncoprotein.
Annual rept. 9 May 95-8 May 96,
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The amino terminus of the Myc oncoprotein is important for many of the biological activities of the protein including transcriptional activation and repression, cellular transformation, and apoptosis. The amino terminus of Myc also contains highly conserved domains necessary for these varied functions of the oncoprotein. A yeast two-hybrid screen of a human cDNA library performed in our lab has yielded a novel factor that interacts with one of these conserved domains, Myc Homology Region II MHR II. Analysis of this novel protein to discern potential effects on Myc function has yielded interesting results. Since MHR II is required by Myc to bring about cellular transformation, the effect of this clone on activated H-ras transformation was assessed. C3H10T12 fibioblasts were stably transfected with both activated human H-ras and the MHR II-associating pmtein, and focus formation was determined. The novel factor appears to be able to cooperate with H-ras to transform this cultured cell line. Another surprising potential effect on Myc function is its apparent ability to repress the transcriptional activity of Myc. Transient transfections in C3H10OT12 cells utilizing the GAL4 reporter system and various deletion mutants of the v-Myc amino terminus have initially implicated the novel protein as a general repressor of transcription, since it not only suppresses Myc transactivation but also that of the potent activator vP16. Further analysis to assess what contribution this new factor has on Mycs other functions is underway.