Mammalian fatty acid synthase and O-GlcNAc transferase preferentially interact via their respective N-terminal regions

Fatty Acid Synthase (FASN) is a central enzyme in the <i>de novo</i> lipogenesis pathway. By producing fatty acids, FASN is implicated in numerous crucial cellular processes, but it is also frequently overexpressed in cancer. <i>O</i>-GlcNAc Transferase (OGT) governs the addition of N-acetylglucosamine residues onto cytosolic, nuclear and mitochondrial proteins. Like FASN, OGT actively participates in carcinogenesis. We previously showed that OGT regulates FASN in different <i>ex vivo</i> and <i>in vivo</i> models. Reciprocally, FASN promotes OGT expression and activity. The two enzymes physically interact together and contribute to cancer cell survival. It is therefore fundamental to define the respective interaction region of each enzyme to explore new therapeutic solutions for patients suffering from cancer. By using the hepatocarcinoma cell line Hep3B, we show thanks to two series of deletion mutants that both enzymes preferentially interact <i>via</i> their respective N-terminal regions. Analysis of the <i>O</i>-GlcNAc status of the various FASN deletion mutants shows that stronger interaction with OGT correlates with higher glycosylation, suggesting that OGT catalyzes the transfer of GlcNAc with limited substrate specificity.