Chemical synthesis of the ATAD2 bromodomain.

Due to the emerging importance of the bromodomain binding region in the study of epigenetic effectors and the vast implications for a wide variety of human disease, the bromodomain region of human ATPase family AAA+ (ATPases associated with diverse cellular activities) domain-containing protein 2 (ATAD2) was targeted for chemical synthesis. The ATAD2 bromodomain (130 aa) was divided into five strategic fragments to be assembled using native chemical ligation with a focus on maximal convergency and efficiency. The fragments were assembled with one cysteine and three thioleucine ligations, unveiling the native alanine and leucine amino acids at the ligation points following metal-free dethiylation. Synthetic highlights of the study are a photolabile dimethoxynitrobenzyl-protected glutamic acid side chain used to impede hydrolysis of the C-terminal Glu-thioester, a thiazolidine-protected thioleucine, and an efficient assembly of three fragments in a single reaction vessel with dual-mode kinetic-standard chemical ligation. With a focus on material throughput and convergency, the five peptide fragments were assembled into the native ATAD2 bromodomain region with a total of three HPLC events in 8% overall yield from the fragments.