Transcription factor Nrf1 is negatively regulated by its O-GlcNAcylation status.

O-Linked N-acetylglucosamine transferase (OGT) was identified as an Nrf1-interacting protein. Herein, we show that Nrf1 enables interaction with OGT and their co-immunoprecipitates are O-GlcNAcylated by the enzyme. The putative O-GlcNAcylation negatively regulates Nrf1/TCF11 to reduce both its protein stability and transactivation activity of target gene expression. The turnover of Nrf1 is enhanced upon overexpression of OGT, which promotes ubiquitination of the CNC-bZIP protein. Furthermore, the serine/theorine-rich sequence of PEST2 degron within Nrf1 is identified to be involved in the protein O-GlcNAcylation by OGT. Overall, Nrf1 is negatively regulated by its O-GlcNAcylation status that depends on the glucose concentrations.