Chemical Proteomic Profiling of Protein Dopaminylation in Colorectal Cancer Cells

Histone dopaminylation is a newly identified epigenetic
mark that
plays a role in the regulation of gene transcription, where an isopeptide
bond is formed between the fifth amino acid of H3 (i.e., glutamine)
and dopamine. Recently, we developed a chemical probe to specifically
label and enrich histone dopaminylation via bioorthogonal chemistry.
Given this powerful tool, we found that histone H3 glutamine 5 dopaminylation
(H3Q5dop) was highly enriched in colorectal tumors, which could be
attributed to the high expression level of its regulator, transglutaminase
2 (TGM2), in colon cancer cells. Due to the enzyme promiscuity of
TGM2, nonhistone proteins have also been identified as dopaminylation
targets; however, the dopaminylated proteome in cancer cells still
remains elusive. Here, we utilized our chemical probe to enrich dopaminylated
proteins from colorectal cancer cells in a bioorthogonal manner and
performed the chemical proteomics analysis. Therefore, 425 dopaminylated
proteins were identified, many of which are involved in nucleic acid
metabolism and transcription pathways. More importantly, a number
of dopaminylation sites were identified and attributed to the successful
application of our chemical probe. Overall, these findings shed light
on the significant association between cellular protein dopaminylation
and cancer development, further suggesting that targeting these pathways
may become a promising anticancer strategy.