Glucose-regulated O-GlcNAcylation of DNMT1 inhibits DNA methyltransferase activity and maintenance of genomic methylation

The production of O -GlcNAc for protein O -GlcNAcylation is highly tuned to the metabolic state of the cell and thus can serve as a nutrient sensor responding to changes in metabolic pathways. We report here that excess glucose leads to increased O GlcNAcylation of DNMT1, resulting in inhibition of DNA methyltransferase 1 (DNMT1) function and alterations to the epigenome. Using mass spectrometry and complementary alanine mutation experiments, we identified S878 as the major residue that is O GlcNAcylated on DNMT1. Functional studies reveal that O -GlcNAcylation of DNMT1-S878 reduces its DNA methyltransferase activity. Treatment of cells with prolonged high glucose induces loss of DNA methylation, preferentially at partially methylated domains (PMDs). We further find that the high glucose-induced DNA methylation loss is attenuated in cells expressing DNMT1-S878A. These results establish O -GlcNAcylation of DNMT1 as a mechanism through which the epigenome is regulated by glucose metabolism and implicates a role for glycosylation of DNMT1 in metabolic diseases characterized by hyperglycemia.