Defining the functional domains of the MC29 v-Myc protein

Soyoung Min, Purdue University

Abstract

To understand the mechanism by which Myc contributes to cell growth and transformation, functional domains of the MC29 v-Myc protein have been defined using the mouse fibroblast cell line C3H10T1/2. The carboxy terminal transforming region of v-Myc has been defined precisely as a.a.329 to a.a.410 by generating a series of deletion mutations between a.a.244 and a.a.410 of the protein and using ras-myc co-transformation of C3H10T1/2 cells as a functional assay. Additional studies on selected mutations from this series demonstrated that the site-specific DNA-binding property of v-Myc is required for co-transforming activity. Interestingly, the nuclear localization signal sequence of v-Myc can be deleted without impairing the co-transforming ability of the protein, suggesting that v-Myc is multifunctional and can contribute to transformation while localized to the nucleus or to the cytoplasm of cells. Intrigued by the observed structural similarity between v-Myc and several eukaryotic transcription factors, the transcription activation potential of v-Myc was investigated using the yeast GAL4 vector system. The results indicated that the amino terminus of the protein (a.a.1-244) encodes transcription activation activity and that within this region, two subdomains (a.a.1-42 and a.a.90-219), each with a distinct ability to activate transcription, were identified. The importance of transcription activation activity to the ability of v-Myc to cooperate with activated ras was demonstrated using C3H10T1/2 co-transformation assays. Additional transcription activation studies using Max, a protein binding partner of Myc, failed to reveal the presence of a transcription activation domain within this protein, suggesting that the potential of the Myc/Max complex to influence gene expression relies primarily on the amino terminus of Myc. Further studies on the transcription activation domain of v-Myc provided evidence for protein-protein interactions mediated by this region, many of which seem to be important for transformation as well as cell proliferation. This study has correlated the function of v-Myc as a potential transcription factor with the function of v-Myc in cellular transformation and has defined v-Myc regions specifying potential protein-protein interactions that contribute to cellular transformation in ways yet to be defined.

Degree

Ph.D.

Advisors

Taparowsky, Purdue University.

Subject Area

Molecular biology|Biochemistry

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