Development and Application of Chemoenzymatic Tools to Investigate Site-Specific Protein ADP-Ribosylation

Herein I have developed the first technologies to install mono- and poly-ADP-ribosylation at specific sites on synthetic peptides and full-length proteins. Historically, chemical and topological complexities associated with ADP-ribosylation have stymied progress in this area. To overcome this, I have identified enzymes capable of: (i) installing ADP-ribose specific side chain functionalities on synthetic peptides, and (ii) elongating ADP-ribose chains from mono-ADP-ribosylated substrate peptides. These enzymes are highly efficient and promiscuous in regard to substrate peptide amino acid sequence. ADP-ribosylated peptides are compatible with N-terminal and C-terminal protein ligation technologies to afford assembly of homogenous, full-length proteins bearing ADP-ribosylation at user-defined sites. These reagents were then employed to address fundamental questions regarding the structure, function, and regulation of different ADP-ribose:protein linkage types and specific ADP-ribosylation sites on chromatin and chromatin associated proteins. Overall, the work discussed here reveals basic chemical and biological principles of arginine, aspartate, glutamate, and serine ADP-ribosylation and enables new strategies to interrogate the biochemical consequences of this widespread protein modification in human physiology and disease.