Quantitative Phosphoproteomics Reveals Crosstalk Between Phosphorylation and O-GlcNAc in the DNA Damage Response Pathway

The modification of intracellular proteins by monosaccharides of O-linked linked β-N-acetylglucosamine (O-GlcNAc) is thought to mediate proteins by regulating protein phosphorylation, either by modifying and modulating protein kinases or by competing with phosphorylation for hydroxyl residues. To provide molecular insight into the pathways regulated by O-GlcNAc that promote survival in basal conditions or during cellular stress, we have utilized SILAC-based quantitative proteomics to carry out comparisons of site-specific phosphorylation in OGT wild-type (WT) and Null cells. Quantitation of the phosphoproteome demonstrated that out of 5,529 serine/threonine/tyrosine phosphorylated sites, 231 phosphosites were upregulated and 133 downregulated in the absence of O-GlcNAc. The data identified widespread changes in the phosphoproteome upon removal of O-GlcNAc, suggesting that O-GlcNAc regulates processes such as the cell cycle, genomic stability, inflammatory responses and lysosomal biogenesis.