Abstract
O‐GlcNAc Transferase (OGT) is an essential glycosyltransferase that catalyzes the attachment of N‐acetylglucosamine (GlcNAc) to serines and threonines of numerous nuclear and cytoplasmic proteins. Global O‐GlcNAcylation is sensitive to changes in the concentration of OGT's substrate, UDP‐GlcNAc, which is affected by cellular glucose levels. Increased O‐GlcNAcylation is associated with widespread changes in gene expression, but the molecular mechanisms underlying these changes remain poorly understood. Recently, OGT was shown to catalyze another post‐translational modification: the cleavage of the cell cycle regulator Host Cell Factor 1 (HCF‐1). We will describe our work on the unusual mechanism of HCF‐1 cleavage by OGT. We will show that cleavage requires UDP‐GlcNAc as a cosubstrate, implying that HCF‐1 cleavage, like O‐GlcNAcylation, is coupled to UDP‐GlcNAc concentration. Hence, key cell cycle regulatory functions of HCF‐1 are linked to nutrient levels through a remarkable proteolytic action of OGT.
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