• COCA-seq is a novel genome-wide method that chemoselectively profiles O-GlcNAc-associated open chromatin regions, combining DNase-seq and metabolic glycan labeling.
• The method demonstrates dual fidelity in O-GlcNAc chemoselectivity and open chromatin specificity, validated across low- and high-throughput levels.
• Application to doxorubicin-resistant breast cancer reveals key regulatory genes and transcription factors, integrating with RNA-seq to uncover mechanisms of drug resistance.
• COCA-seq provides a versatile tool for deciphering the role of O-GlcNAcylation in chromatin accessibility and gene regulation across diverse biological contexts.