PPM - How Is Protein Arginine Methylation Coordinated with Other Modifications to Effect Biological Function

With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Steven Clarke from the University of California, Los Angeles to investigate how organisms enhance their resilience and survival by modifying proteins inside cells. Proteins are long chains of amino acids that are folded in precise manners to carry out their functions inside cells. Organisms have also developed ways of modifying specific amino acids to expand “nature’s inventory” of chemical structures in proteins. These modifications are important for optimizing protein function and organismal survival when placed under stress. This project is focused on enzymes that catalyze the transfer of simple methyl groups to arginine amino acid residues, with the goal of defining how this chemical modification works in harmony with other modified amino acids to control how genes turn on and off in cells in non-physiologically cold or basic pH conditions. This project contributes substantially to the training of undergraduate students, graduate students, and postdoctoral scholars, preparing them for independent careers in defining chemical processes within cells and understanding cell survival strategies. Outreach activities target for training the young Americans who represent the next generations of researchers. This research project focuses on posttranslational modifications of proteins and specifically characterizes the role of mammalian protein arginine methylation and its relationship with other covalent modifications. The project is centered on the modifications catalyzed by the protein arginine methyltransferase 7 (PRMT7), a unique enzyme in the family PRMT that exclusively forms the monomethyl arginine (MMA) derivative, specifically in R-X-R sequences. PRMT7 is most active under conditions of physiological stress. However, there is currently a large knowledge gap in understanding the physiological function of MMA, particularly in relationship to other modifications (e.g. phosphorylation) of nearby amino acid residues. A central question is whether the MMA modification is stable and required for normal protein function or whether it represents a reversible modification that can regulate protein function. The biochemistry of the interactions of PRMT7 and protein kinases need to be studied to distinguish between regulatory roles and structural roles of protein methylation. Histones, the “poster children” in crosstalk among different protein modifications, undergo arginine and lysine methylation, lysine acetylation, lysine ubiquitylation, and serine and threonine phosphorylation. These modifications make up the “histone code” that determines which genes are activated. The interactions of protein arginine methylation with other types of histone modifications need to be defined. While there is clear evidence for regulatory mechanisms of many protein kinases and other types of modification enzymes, there is little understanding of how the activity of the PRMT enzymes are regulated. PRMT7’s in vitro activity is activated under cellular temperature stress (cold) and pH stress (alkaline) conditions, but nothing is known about PRMT7 regulation in vivo. Experiments are proposed to identify PRMT7 substrates in living cells and determine their stoichiometry in response to stress conditions. Particular attention is paid to identifying small molecule or protein activators of PRMT7. The results of these studies can distinguish regulatory versus functional roles for protein arginine methylation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.