Ligand-Directed Self-Assembling Chimeras for Targeted Protein O-GlcNAcylation

Precise control of protein-specific O-GlcNAcylation in cells remains a major challenge. Chemically induced proximity (CIP) offers a promising path forward, but its application to targeted protein O-GlcNAcylation has been limited by the lack of ligands that can bind the O-GlcNAc transferase (OGT) without inhibiting its catalytic function. Here, we repurpose a potent OGT inhibitor into a noninhibitory covalent probe using ligand-directed release chemistry (LDR). The resulting ligands covalently label OGT while preserving its enzymatic activity. Building on this scaffold, we developed a self-assembling O-GlcNAcylation Targeting Chimera (OGTAC) that recruits OGT to its native substrate casein kinase IIα (CK2α) in living cells, selectively elevating CK2α O-GlcNAcylation without affecting global modification levels. This new class of self-assembling chimeras covalently engages OGT to induce protein-specific O-GlcNAcylation, offering a versatile platform for dissecting and controlling this essential modification in living cells. Our findings open the door to next-generation OGTACs and related therapeutic strategies for the targeted modulation of the O-GlcNAc signaling.