CONTROL OF EUCARYOTIC FUNCTION BY METHYLATION

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DESCRIPTION (provided by applicant): We will investigate how physiological functions are controlled by methylation reactions, focusing on the enzymes that catalyze the modification of protein arginine, lysine, and isoaspartyl residues. We are especially interested in methyltransferases that are involved in signal transduction and metabolic regulatory pathways where the presence or absence of the methyl group can modulate the function of the methyl-accepting species. These reactions are important in protecting organisms from environmental stresses and from the accumulation of spontaneous damage in aging cells. We will also develop methods to identify new types of methyltransferases that may catalyze previously unrecognized reactions in these pathways. We will determine the enzymology and functional roles of new members of the eucaryotic family of protein arginine methyltransferases (PRMTs). These enzymes alter the ability of the arginine residue to interact with RNA, DNA, and protein partners and have been shown to have roles in gene regulation, DNA repair, and intracellular signaling pathways. We will focus our work on mammalian systems, but will also use yeast and trypanosomes as model systems. We will pay special attention to the human PRMT7 protein that has been implicated in tumor formation and stem cell survival. Our overall goal is to establish the complete cast of characters of the enzymes that catalyze these modifications in nature so that their functions, especially in signaling and gene regulation in health and disease, can be fully understood. We will characterize new roles in intracellular signaling for the protein repair L-isoaspartyl/D-aspartyl methyltransferase. Here, we will utilize both mouse and worm (Caenorhabditis elegans) systems to explore the relationships between the accumulation of age-damaged proteins, their recognition by the protein repair methyltransferase, and the responses of the insulin/insulin-like signaling system to increase stress resistance and longevity. We will test several hypotheses to explain the physiological role of the linkage, including direct recognition of damaged proteins or methylated proteins by either the signaling pathway itself or a transcriptional system that upregulates one or more crucial members of the signaling pathway. We will determine the role of lysine protein methylation reactions in the translational apparatus, including ribosomal proteins and elongation factors. We will work in both yeast and mammalian cells to understand how the modifications of ribosomal proteins and eEF1A contribute to translational control and resistance to environmental toxins. Finally, we will use bioinformatic and biochemical approaches to search for and to characterize new types of methyltransferases in both yeast and humans. We are especially interested in identifying potential novel sites of methyltransferase inhibition associated with elevated plasma homocysteine levels in humans that have been linked to cardiovascular and neurological diseases. PUBLIC HEALTH RELEVANCE: Our work focuses on how the modification of proteins by the addition of methyl groups can control body function, including pathways of signal transduction in metabolism and macromolecular assembly. We are also interested in how these pathways are altered in cancer and diseases associated with aging.