Chemoproteomic profiling reveals histone H4 dopaminylation inhibiting cell growth

Dopaminylation, the covalent attachment of dopamine to the side chain of glutamine in proteins, represents a newly characterized class of posttranslational modifications. Because of the limited identification of substrates, the functions and molecular mechanisms associated with dopaminylation remain largely uncharacterized. Using an alkyne-functionalized dopamine probe, we developed a method for selectively enriching dopaminylated proteins in whole-cell systems. This approach provided a comprehensive resource of 4,133 dopamine-enriched protein candidates and peptide-level analysis with acid-cleavable tags identified 1,181 putative dopaminylated proteins, including histone H4 dopaminylation at Q27 (H4Q27dop), which we further validated. Functionally, H4Q27dop acts as a transcriptional repressor in a neuroblastoma model, where it blocks CEBPD binding at the CCND1 promoter, leading to transcriptional downregulation of CCND1 and subsequent suppression of cell proliferation. Our findings provide both a valuable resource of dopaminylated substrate proteins and a distinct mechanistic insight into how dopamine regulates neuroblastoma cell growth.