Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Jonelle White - University of California-Los Angeles
Co-Author(s): Maria Dzialo and Qais Al-Hadid, UCLA, Los Angeles, CA
Protein modification by methylation can promote recognition by binding partners or modulation of activity. Proteins of the translational apparatus are known to be methylated by a variety of methyltransferases but the functional consequences of this reaction are largely unknown. Defects in translation have been linked to a number of diseases, including cancer. In this work, I hypothesize that the methylation of ribosomal proteins and elongation factors is important to cell survival and understanding these processes can have important implications to human health.
In our work, we have used the yeast model system, Saccharomyces cerevisiae, where genetic and biochemical tools have been developed. Previous work has identified 10 methyltransferases that modify ribosomal proteins, four species that modify the major elongation factor EF1A, and at least one additional enzyme that can potentially modify a mitochondrial translational component. We have performed growth assays on plates and in liquid media of wild type and mutant strains lacking one or more of the methyltransferases with and without inhibitors of translation including cycloheximide and anisomycin. We have also performed analyses of yeast proteins labeled with S-adenosyl-[methyl-3H]-methionine in wild type and mutant cells.
Interestingly, we have found that some mutant strains grow better with ribosome binding translational inhibitors and some grow more poorly. For example, with cycloheximide, cells lacking the methyltransferase that modifies the large subunit ribosomal protein Rpl42ab grow more poorly than wild type cells, but nine other mutants that are defective in ribosomal protein methylation grow better.
We conclude from these studies that ribosomal protein methylation can alter the structure of the ribosome to change their sensitivity to ribosome binding antibiotics. In future work, we plan to extend these studies to the methyltransferases involved in the methylation of EF1A. We will measure growth in various mutants. Additionally, we will examine the role of the Ykl162C protein, a putative methyltransferase targeted to the mitochondria, which may modify the distinct ribosomes of this organelle. This protein is homologous to a recently described human protein arginine methyltransferase. I will perform in vitro methylation assays, cation exchange chromatography, amino acid hydrolysis and phenotype assays to detect the substrate of this enzyme and determine its possible role in translation.Not Submitted
Funder Acknowledgement(s): National Science Foundation- LSAMP Bridge to Doctorate; NIH Cellular & Molecular Biology Training Grant GM007185; Eugene V. Cota-Robles Fellowship
Faculty Advisor: Steven G. Clarke, email@example.com