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      A little sugar goes a long way: The cell biology of O-GlcNAc

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      The Journal of Cell Biology

      The Rockefeller University Press

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          Abstract

          Unlike the complex glycans decorating the cell surface, the O-linked β- N-acetyl glucosamine (O-GlcNAc) modification is a simple intracellular Ser/Thr-linked monosaccharide that is important for disease-relevant signaling and enzyme regulation. O-GlcNAcylation requires uridine diphosphate–GlcNAc, a precursor responsive to nutrient status and other environmental cues. Alternative splicing of the genes encoding the O-GlcNAc cycling enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) yields isoforms targeted to discrete sites in the nucleus, cytoplasm, and mitochondria. OGT and OGA also partner with cellular effectors and act in tandem with other posttranslational modifications. The enzymes of O-GlcNAc cycling act preferentially on intrinsically disordered domains of target proteins impacting transcription, metabolism, apoptosis, organelle biogenesis, and transport.

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          Most cited references 120

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          Phosphorylation and functions of the RNA polymerase II CTD.

          The C-terminal repeat domain (CTD), an unusual extension appended to the C terminus of the largest subunit of RNA polymerase II, serves as a flexible binding scaffold for numerous nuclear factors; which factors bind is determined by the phosphorylation patterns on the CTD repeats. Changes in phosphorylation patterns, as polymerase transcribes a gene, are thought to orchestrate the association of different sets of factors with the transcriptase and strongly influence functional organization of the nucleus. In this review we appraise what is known, and what is not known, about patterns of phosphorylation on the CTD of RNA polymerases II at the beginning, the middle, and the end of genes; the proposal that doubly phosphorylated repeats are present on elongating polymerase is explored. We discuss briefly proteins known to associate with the phosphorylated CTD at the beginning and ends of genes; we explore in more detail proteins that are recruited to the body of genes, the diversity of their functions, and the potential consequences of tethering these functions to elongating RNA polymerase II. We also discuss accumulating structural information on phosphoCTD-binding proteins and how it illustrates the variety of binding domains and interaction modes, emphasizing the structural flexibility of the CTD. We end with a number of open questions that highlight the extent of what remains to be learned about the phosphorylation and functions of the CTD.
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            Metabolic plasticity in stem cell homeostasis and differentiation.

            Plasticity in energy metabolism allows stem cells to match the divergent demands of self-renewal and lineage specification. Beyond a role in energetic support, new evidence implicates nutrient-responsive metabolites as mediators of crosstalk between metabolic flux, cellular signaling, and epigenetic regulation of cell fate. Stem cell metabolism also offers a potential target for controlling tissue homeostasis and regeneration in aging and disease. In this Perspective, we cover recent progress establishing an emerging relationship between stem cell metabolism and cell fate control. Copyright © 2012 Elsevier Inc. All rights reserved.
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              Diabetic Hyperglycemia activates CaMKII and Arrhythmias by O linked Glycosylation

              Summary Ca2+-Calmodulin dependent protein kinase II (CaMKII) is a regulatory node in heart and brain, and its chronic activation can be pathological. CaMKII activation seen in heart failure can directly induce pathological changes in ion channels, Ca2+ handling and gene transcription. 1 Here we discover a novel mechanism linking CaMKII and hyperglycemic signaling in diabetes mellitus, which is a key risk factor for heart 2 and neurodegenerative diseases. 3,4 Acute hyperglycemia causes covalent modification of CaMKII by O-linked N-acetylglucosamine (O-GlcNAc). O-GlcNAc modification of CaMKII at Ser-279 activates CaMKII autonomously, creating molecular memory even after [Ca2+] declines. O-GlcNAc modified CaMKII is increased in heart and brain from diabetic humans and rats. In cardiomyocytes, increased [glucose] significantly enhances CaMKII-dependent activation of spontaneous sarcoplasmic reticulum (SR) Ca2+ release events that can contribute to cardiac mechanical dysfunction and arrhythmias. 1 These effects were prevented by pharmacological inhibition of O-GlcNAc signaling or genetic ablation of CaMKIIδ. In intact perfused hearts, arrhythmias were enhanced by increased [glucose] via O-GlcNAc-and CaMKII-dependent pathways. In diabetic animals, acute blockade of O-GlcNAc inhibited arrhythmogenesis. Thus, O-GlcNAc modification of CaMKII is a novel signaling event in pathways that may contribute critically to cardiac and neuronal pathophysiology in diabetes and other diseases.
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                Author and article information

                Journal
                J Cell Biol
                J. Cell Biol
                jcb
                jcb
                The Journal of Cell Biology
                The Rockefeller University Press
                0021-9525
                1540-8140
                30 March 2015
                : 208
                : 7
                : 869-880
                Author notes
                Correspondence to Michelle R. Bond: bondmr@ 123456mail.nih.gov ; or John A. Hanover: jah@ 123456helix.nih.gov
                Article
                201501101
                10.1083/jcb.201501101
                4384737
                25825515

                This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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