Role Of O Glcnac On The Rna Polymerase Ii Carboxyl Terminal Domain

Author : Dacheng Fan
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

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Download or read book Investigating the O-glcnac Cycling Enzymes written by Dacheng Fan and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: O-GlcNAcylation is a unique post-translational modification (PTM) of the monosaccaride O-linked N-acetylglucosamine (O-GlcNAc) covalently attached onto the serine or threonine residues of intracellular proteins. Controlled by a single pair of enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), this PTM has been found on thousands of protein substrates involved in a variety of biological processes such as transcription, translation, metabolism, signaling, and structure, affecting the stability, translocalization, and cellular functions of the modified proteins. The homeostasis of O-GlcNAcylation is crucial for cells and organisms to maintain normal physiology, and its dysregulation is closely related to a number of diseases including diabetes, neurodegeneration, cardiovascular disorder, and different types of cancers. However, the mechanism through which OGT and OGA achieve the homeostasis remains largely mysterious, which significantly limits the potential of O-GlcNAc as a diagnostic or therapeutic target. This dissertation addresses this issue through the studies of substrate recognition, enzymatic activity, and biological functions of the O-GlcNAc cycling enzymes. A GlcNAc electrophilic probe (GEP) is developed to rapidly identify key amino acid residues on OGT that are essential for its substrate recognition by generating distinct labeling patterns on both OGT and the protein substrate. Application of GEP reveals ladders of asparagine and aspartate residues spanning the inner surface of OGT's entire tetratricopeptide repeat (TPR) domain are functionally critical for OGT binding and glycosylating its substrate, while no outside residues are found to be important, supporting the hypothesis that OGT utilizes its full-length TPR domain to wrap its substrate for glycosylation. Next, a chemical analog of GEP is designed, synthesized, and characterized as the first reported targeted covalent inhibitor of OGT with validated specificity in cells. Finally, the distributive O-GlcNAcylation mechanism of RNA polymerase II C-terminal domain is elucidated, aiding in future research about the regulatory role of this PTM in gene transcription. Taken together, the developed chemical tools and discovered glycosylation mechanism are expected to facilitate the understanding of substrate recognition, enzymatic activity, and biological functions of OGT and OGA, and to inspire novel drug discovery targeting O-GlcNAc.