Numerous biological events need to be orchestrated at an epigenetic level upon defining cellular fate. Among the key epigenetic regulators are protein methyltransferases (PMTs), which methylate specific Arg/Lys residues with S-adenosyl-L- methionine (SAM) as a cofactor. Whereas many recombinant PMTs are active in vitro, their cellular activities can largely depend on the presence of distinct PMT isoforms or complexes. Such context- dependent complexity makes it challenging to solely rely on conventional methods to elucidate the targets of PMTs. The flexible substrate-recognizing patterns of PMTs, together with their highly- conserved SAM-binding motifs, also made it challenging to develop PMT inhibitors with potency and selectivity. A long-term goal of the project is to elucidate and manipulate methyltransferase- involved epigenetic for disease diagnosis and treatments. The objective of this application is to use SAM mimics as probes to profile cell-type-specific substrates of PMTs and to perturb PMTs in a specific manner. Here an integrative Bioorthogonal Profiling of Protein Methylation (BPPM) will be implemented to dissect the substrates of designated PMTs in relevant biological contexts. A subtype of methylation events associated with specific biological processes will be further validated with well-established methods. Their functional roles will be examined in the context of cancer malignancy or stem cell reprogramming. In parallel, stable SAM analogues will be pursued as target-specific inhibitors against PMTs. The completion of this proposal will unambiguously reveal the substrates of multiple PMTs and characterize high-quality PMT inhibitors in relevant cellular contexts. The impact of these substrate-profiling and inhibitor-identifying strategies further lie n their general applicability to other methyltransferases.
This proposal is expected to uncover the targets of biologically relevant methyltransferases and expand the current collection of methyltransferase inhibitors. The methylation events associated with disease malignancy will be validated and the corresponding inhibitors will be characterized. This work is expected to elicit disease-associated biology and lead to potential therapeutic reagents.
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