Distinct OGT-Binding Sites Promote HCF-1 Cleavage |
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| Authors: | Tanja Bhuiyan Patrice Waridel Vaibhav Kapuria Vincent Zoete Winship Herr |
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| Affiliation: | 1. Center for Integrative Genomics, University of Lausanne, Génopode, Lausanne, Switzerland.; 2. Protein Analysis Facility, Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Génopode, Lausanne, Switzerland.; 3. Molecular Modeling Group, Swiss Institute of Bioinformatics, Génopode, Lausanne, Switzerland.; Stanford University, UNITED STATES, |
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| Abstract: | Human HCF-1 (also referred to as HCFC-1) is a transcriptional co-regulator that undergoes a complex maturation process involving extensive O-GlcNAcylation and site-specific proteolysis. HCF-1 proteolysis results in two active, noncovalently associated HCF-1N and HCF-1C subunits that regulate distinct phases of the cell-division cycle. HCF-1 O-GlcNAcylation and site-specific proteolysis are both catalyzed by O-GlcNAc transferase (OGT), which thus displays an unusual dual enzymatic activity. OGT cleaves HCF-1 at six highly conserved 26 amino acid repeat sequences called HCF-1PRO repeats. Here we characterize the substrate requirements for OGT cleavage of HCF-1. We show that the HCF-1PRO-repeat cleavage signal possesses particular OGT-binding properties. The glutamate residue at the cleavage site that is intimately involved in the cleavage reaction specifically inhibits association with OGT and its bound cofactor UDP-GlcNAc. Further, we identify a novel OGT-binding sequence nearby the first HCF-1PRO-repeat cleavage signal that enhances cleavage. These results demonstrate that distinct OGT-binding sites in HCF-1 promote proteolysis, and provide novel insights into the mechanism of this unusual protease activity. |
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