Mechanisms of OGT-mediated HCF-1 protein maturation

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State: Public
Version: After imprimatur
Serval ID
serval:BIB_37447C135825
Type
PhD thesis: a PhD thesis.
Collection
Publications
Title
Mechanisms of OGT-mediated HCF-1 protein maturation
Author(s)
Bhuiyan T.
Director(s)
Herr W.
Institution details
Université de Lausanne, Faculté de biologie et médecine
Address
Faculté de biologie et de médecineUniversité de LausanneCH-1015 LausanneSUISSE
Publication state
Accepted
Issued date
06/2015
Language
english
Number of pages
193
Abstract
Post-translational protein modifications are crucial for many fundamental cellular and extracellular processes and greatly contribute to the complexity of organisms. Human HCF-1 is a transcriptional co-regulator that undergoes complex protein maturation involving reversible and irreversible post-translational modifications. Upon synthesis as a large precursor protein, HCF-1 undergoes extensive reversible glycosylation with β-N-acetylglucosamine giving rise to O-linked-β-N-acetylglucosamine (O-GlcNAc) modified serines and threonines. HCF-1 also undergoes irreversible site-specific proteolysis, which is important for one of HCF-1's major functions - the regulation of the cell-division cycle. HCF-1 O-GlcNAcylation and site-specific proteolysis are both catalyzed by a single enzyme with an unusual dual enzymatic activity, the O-GlcNAc transferase (OGT). HCF-1 is cleaved by OGT at any of six highly conserved 26 amino acid repeated sequences (HCF-1PRO repeats), but the mechanisms and the substrate requirements for OGT-mediated cleavage are not understood. In the present work, I characterized substrate requirements for OGT-mediated cleavage and O-GlcNAcylation of HCF-1. I identified key elements within the HCF-1PRO-repeat sequence that are important for proteolysis. Remarkably, an invariant single amino acid side-chain within the HCF-1PRO-repeat sequence displays particular OGT-binding properties and is essential for proteolysis. Additionally, I characterized substrate requirements for proteolysis outside of the HCF-1PRO repeat and identified a novel, highly O-GlcNAcylated OGT-binding sequence that enhances cleavage of the first HCF-1PRO repeat. These results link OGT association and its O-GlcNAcylation activities to HCF-1PRO-repeat proteolysis.
Keywords
HCF-1, OGT, O-GlcNAcylation, proteolysis, protein-protein interactions, crystal structure
Create date
03/09/2015 15:41
Last modification date
20/08/2019 14:25
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