Thomas L. Mason Professor Emeritus of Biochemistry and Molecular Biology, University of Massachusetts Email: tmason@biochem.umass.edu Ph.D.: University of Minnesota Molecular Biology of the Mitochondrial Translation System; Protein Expression in Bacteria and Yeast We study the formation and function of the mitochondrial ribosome in the yeast Saccharomyces cerevisiae. The mitochondrial translation system is not required for cell viability in yeast, providing an excellent experimental model for the molecular genetic analysis of the conserved and divergent features of the mitochondrial ribosome. In yeast, the two ribosomal RNAs and a single ribosomal protein, Var1, are products of mitochondrial genes, and the remaining ribosomal proteins are encoded in the nucleus. Current studies in our laboratory focus on proteins and nucleotide modification enzymes required for formation of the highly conserved peptidyl transferase center in the large ribosomal subunit and on the unusual Var1 protein, which is an essential component of the small ribosomal subunit. We recently uncoupled the formation of the mitochondrial ribosome from its function by relocating the VAR1 gene from mitochondrial DNA to the nucleus. This greatly facilitates our mutational analyses of nucleus-encoded ribosomal proteins and nucleotide modification enzymes, and we have also used this system to identify nuclear regulatory genes that specifically control the expression of mitochondrial VAR1 posttranscriptionally. Representative publications: Sanchirico, M.E., Fox, T.D. and Mason, T.L. (1998) Accumulation of mitochondrially synthesized Saccharomyces cerevisiae Cox2p and Cox3p depends on targeting information in untranslated portions of their mRNAs. EMBO J., in press. Mason, T.L. (1998) Functional aspects of the three modified nucleotides in the yeast mitochondrial large subunit rRNA. In: Modification and Editing of RNA: The Alteration of RNA Structure and Function, (H. Grosjean and R. Benne, eds.), ASM Press, Washington, D.C., pp. 273-280. Pan, C. and Mason, T.L. (1997) Functional analysis of ribosomal protein L2 in yeast mitochondrial ribosomes. J. Biol. Chem. 272, 8165-8171. Mason, T.L., Pan, C., Sanchirico, M.E. and Sirum-Connolly, K. (1996) Molecular genetics of the peptidyl transferase center and the unusual Var1 protein in yeast mitochondrial ribosomes. Experientia 52, 1148-1157. Sanchirico, M., Tzellas, A., Fox, T.D., Conrad-Webb, H., Perlman, P.S. and Mason, T.L. (1995) Relocation of the unusual VAR1 gene from the mitochondrion to the nucleus. Biochemistry and Cell Biology 73, 987-995. |
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