Quantitative time-resolved chemoproteomics reveals that stable O -GlcNAc regulates box C/D snoRNP biogenesis

Significance In mammalian cells, more than 1,000 intracellular proteins are posttranslationally modified with O -linked GlcNAc ( O -GlcNAc), which regulates many important biological processes. The O -GlcNAc modification has been found to dynamically cycle on and off the modified proteins. How O -GlcNAc affects protein stability remains to be investigated at the proteome level. In this work, we developed a quantitative time-resolved proteomic strategy to analyze the turnover dynamics of O -GlcNAcylated proteins. We discovered that not all protein O -GlcNAcylation events were reversible and that a subset of O -GlcNAcylated proteins exhibited minimal removal of O -GlcNAc or degradation of protein backbones. Our work reveals stable O -GlcNAc as an important regulatory mechanism for stabilizing proteins, such as core proteins of box C/D small nucleolar ribonucleoprotein complexes.