Medical Biochemistry Commons^™

Three-Dimensional Context Rather Than Nls Amino Acid Sequence Determines Importin Α Subtype Specificity For Rcc1., Rajeshwer S. Sankhala, Ravi K. Lokareddy, Salma Begum, Ruth A. Pumroy, Richard E. Gillilan, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Active nuclear import of Ran exchange factor RCC1 is mediated by importin α3. This pathway is essential to generate a gradient of RanGTP on chromatin that directs nucleocytoplasmic transport, mitotic spindle assembly and nuclear envelope formation. Here we identify the mechanisms of importin α3 selectivity for RCC1. We find this isoform binds RCC1 with one order of magnitude higher affinity than the generic importin α1, although the two isoforms share an identical NLS-binding groove. Importin α3 uses its greater conformational flexibility to wedge the RCC1 β-propeller flanking the NLS against its lateral surface, preventing steric clashes with its Armadillo-core. Removing …

Synergy Of Two Low-Affinity Nlss Determines The High Avidity Of Influenza A Virus Nucleoprotein Np For Human Importin Α Isoforms., Wei Wu, Rajeshwer S. Sankhala, Tyler J Florio, Lixin Zhou, Nhan L.T. Nguyen, Ravi K. Lokareddy, Gino Cingolani, Nelly Panté

Department of Biochemistry and Molecular Biology Faculty Papers

The influenza A virus nucleoprotein (NP) is an essential multifunctional protein that encapsidates the viral genome and functions as an adapter between the virus and the host cell machinery. NPs from all strains of influenza A viruses contain two nuclear localization signals (NLSs): a well-studied monopartite NLS1 and a less-characterized NLS2, thought to be bipartite. Through site-directed mutagenesis and functional analysis, we found that NLS2 is also monopartite and is indispensable for viral infection. Atomic structures of importin α bound to two variants of NLS2 revealed NLS2 primarily binds the major-NLS binding site of importin α, unlike NLS1 that associates …

Xenobiotic-Induced Activation Of Human Aryl Hydrocarbon Receptor Target Genes In Drosophila Is Mediated By The Epigenetic Chromatin Modifiers, Angelina A. Akishina, J. E. Vorontsova, Roman O. Cherezov, Ilja B. Mertsalov, Olga G. Zatsepina, Mikhail S. Slezinger, Vladislav M. Panin, Svetlana Petruk, Grigori N. Enikolopov, Alexander M. Mazo, Olga B. Simonova, Boris A. Kuzin

Department of Biochemistry and Molecular Biology Faculty Papers

Aryl hydrocarbon receptor (AHR) is the key transcription factor that controls animal development and various adaptive processes. The AHR's target genes are involved in biodegradation of endogenous and exogenous toxins, regulation of immune response, organogenesis, and neurogenesis. Ligand binding is important for the activation of the AHR signaling pathway. Invertebrate AHR homologs are activated by endogenous ligands whereas vertebrate AHR can be activated by both endogenous and exogenous ligands (xenobiotics). Several studies using mammalian cultured cells have demonstrated that transcription of the AHR target genes can be activated by exogenous AHR ligands, but little is known about the effects of …

Complex Interplay Of Kinetic Factors Governs The Synergistic Properties Of Hiv-1 Entry Inhibitors., Koree W. Ahn, Michael J. Root

Department of Biochemistry and Molecular Biology Faculty Papers

The homotrimeric HIV-1 envelope glycoprotein (Env) undergoes receptor-triggered structural changes that mediate viral entry through membrane fusion. This process is inhibited by chemokine receptor antagonists (CoRAs) that block Env-receptor interactions and by fusion inhibitors (FIs) that disrupt Env conformational transitions. Synergy between CoRAs and FIs has been attributed to a CoRA-dependent decrease in the rate of viral membrane fusion that extends the lifetime of the intermediate state targeted by FIs. Here, we demonstrated that the magnitude of CoRA/FI synergy unexpectedly depends on FI-binding affinity and the stoichiometry of chemokine receptor binding to trimeric Env. For C-peptide FIs (clinically represented by …

Decorin-Evoked Paternally Expressed Gene 3 (Peg3) Is An Upstream Regulator Of The Transcription Factor Eb (Tfeb) In Endothelial Cell Autophagy., Thomas Neill, Catherine Sharpe, Rick T. Owens, Renato V. Iozzo

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Macroautophagy is a fundamental and evolutionarily conserved catabolic process that eradicates damaged and aging macromolecules and organelles in eukaryotic cells. Decorin, an archetypical small leucine-rich proteoglycan, initiates a protracted autophagic program downstream of VEGF receptor 2 (VEGFR2) signaling that requires paternally expressed gene 3 (PEG3). We have discovered that PEG3 is an upstream transcriptional regulator of transcription factor EB (TFEB), a master transcription factor of lysosomal biogenesis, for decorin-evoked endothelial cell autophagy. We found a functional requirement of PEG3 for TFEB transcriptional induction and nuclear translocation in human umbilical vein endothelial and PAER2 cells. Mechanistically, inhibiting VEGFR2 or AMP-activated protein …

Structural Basis For Selective Inhibition Of Cyclooxygenase-1 (Cox-1) By Diarylisoxazoles Mofezolac And 3-(5-Chlorofuran-2-Yl)-5-Methyl-4-Phenylisoxazole (P6)., Gino Cingolani, Andrea Panella, Maria Grazia Perrone, Paola Vitale, Giuseppe Di Mauro, Cosimo G G. Fortuna, Roger S. Armen, Savina Ferorelli, William L. Smith, Antonio Scilimati

Department of Biochemistry and Molecular Biology Faculty Papers

The diarylisoxazole molecular scaffold is found in several NSAIDs, especially those with high selectivity for COX-1. Here, we have determined the structural basis for COX-1 binding to two diarylisoxazoles: mofezolac, which is polar and ionizable, and 3-(5-chlorofuran-2-yl)-5-methyl-4-phenylisoxazole (P6) that has very low polarity. X-ray analysis of the crystal structures of COX-1 bound to mofezolac and 3-(5-chlorofuran-2-yl)-5-methyl-4-phenylisoxazole allowed the identification of specific binding determinants within the enzyme active site, relevant to generate structure/activity relationships for diarylisoxazole NSAIDs.

The Kinetic Mechanism Of Bacterial Ribosome Recycling., Yuanwei Chen, Akira Kaji, Hideko Kaji, Barry S. Cooperman

Department of Biochemistry and Molecular Biology Faculty Papers

Bacterial ribosome recycling requires breakdown of the post-termination complex (PoTC), comprising a messenger RNA (mRNA) and an uncharged transfer RNA (tRNA) cognate to the terminal mRNA codon bound to the 70S ribosome. The translation factors, elongation factor G and ribosome recycling factor, are known to be required for recycling, but there is controversy concerning whether these factors act primarily to effect the release of mRNA and tRNA from the ribosome, with the splitting of the ribosome into subunits being somewhat dispensable, or whether their main function is to catalyze the splitting reaction, which necessarily precedes mRNA and tRNA release. Here, …

Additional Sex Combs Interacts With Enhancer Of Zeste And Trithorax And Modulates Levels Of Trimethylation On Histone H3k4 And H3k27 During Transcription Of Hsp70., Taosui Li, Jacob W Hodgson, Svetlana Petruk, Alexander Mazo, Hugh W Brock

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: Maintenance of cell fate determination requires the Polycomb group for repression; the trithorax group for gene activation; and the enhancer of trithorax and Polycomb (ETP) group for both repression and activation. Additional sex combs (Asx) is a genetically identified ETP for the Hox loci, but the molecular basis of its dual function is unclear.

RESULTS: We show that in vitro, Asx binds directly to the SET domains of the histone methyltransferases (HMT) enhancer of zeste [E(z)] (H3K27me3) and Trx (H3K4me3) through a bipartite interaction site separated by 846 amino acid residues. In Drosophila S2 cell nuclei, Asx interacts with …

Functional Selectivity Of Gpcr-Directed Drug Action Through Location Bias., Roshanak Irannejad, Veronica Pessino, Delphine Mika, Bo Huang, Philip B. Wedegaertner, Marco Conti, Mark Von Zastrow

Department of Biochemistry and Molecular Biology Faculty Papers

G-protein-coupled receptors (GPCRs) are increasingly recognized to operate from intracellular membranes as well as the plasma membrane. The β 2 -adrenergic GPCR can activate G s -linked cyclic AMP (G s -cAMP) signaling from endosomes. We show here that the homologous human β 1 -adrenergic receptor initiates an internal G s -cAMP signal from the Golgi apparatus. By developing a chemical method to acutely squelch G-protein coupling at defined membrane locations, we demonstrate that Golgi activation contributes significantly to the overall cellular cAMP response. Golgi signaling utilizes a preexisting receptor pool rather than receptors delivered from the cell surface, requiring …

A Delayed H3k27me3 Accumulation After Dna Replication Of Embryonic Stem Cells Opens Chromatin For Lineage Specific Transcription Factors To Bind And Initiate Differentiation, Jingli Cai, Svetlana Petruk, Robyn Sussman, Sina K. Kovermann, Samantha Mariani, Bruno Calabretta, Steven B Mcmahon, Hugh W. Brock, Lorraine Iacovitti, Alexander Mazo

Department of Neuroscience Faculty Papers

Introduction

Pluripotent stem cells (PSCs) have been useful to generate differentiated progenies for cell replacement therapy, and disease models. The Parkinson’s Disease (PD) field was arguably one of the first to have embraced the promise of stem cells. However, regardless of the differentiation protocols used, cultures and grafts continue to contain multiple cell types with midbrain dopamine (mDA) neural progenitors (NPs) and neurons representing only a fraction of total cells in the dish or graft. During cell differentiation, recruitment of transcription factors (TFs) to repressed genes in euchromatin is essential to activate new transcriptional programs, which is impeded by condensed …

The 11s Proteasomal Activator Regγ Impacts Polyglutamine-Expanded Androgen Receptor Aggregation And Motor Neuron Viability Through Distinct Mechanisms., Jill M. Yersak, Heather L. Montie, Erica S. Chevalier-Larsen, Yuhong Liu, Lan Huang, Martin Rechsteiner, Diane E. Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is caused by expression of a polyglutamine (polyQ)-expanded androgen receptor (AR). The inefficient nuclear proteasomal degradation of the mutant AR results in the formation of nuclear inclusions containing amino-terminal fragments of the mutant AR. PA28γ (also referred to as REGγ) is a nuclear 11S-proteasomal activator with limited proteasome activation capabilities compared to its cytoplasmic 11S (PA28α, PA28β) counterparts. To clarify the role of REGγ in polyQ-expanded AR metabolism, we carried out genetic and biochemical studies in cell models of SBMA. Overexpression of REGγ in a PC12 cell model of SBMA increased polyQ-expanded AR aggregation …

Dysregulated Gpcr Signaling And Therapeutic Options In Uveal Melanoma., Vivian Chua, Dominic Lapadula, Clinita Randolph, Jeffrey L. Benovic, Philip B. Wedegaertner, Andrew E. Aplin

Department of Biochemistry and Molecular Biology Faculty Papers

Uveal melanoma is the most common primary intraocular malignant tumor in adults and arises from the transformation of melanocytes in the uveal tract. Even after treatment of the primary tumor, up to 50% of patients succumb to metastatic disease. The liver is the predominant organ of metastasis. There is an important need to provide effective treatment options for advanced stage uveal melanoma. To provide the preclinical basis for new treatments, it is important to understand the molecular underpinnings of the disease. Recent genomic studies have shown that mutations within components of G protein-coupled receptor (GPCR) signaling are early events associated …

Chemical And Structural Characterization Of A Model Post-Termination Complex (Potc) For The Ribosome Recycling Reaction: Evidence For The Release Of The Mrna By Rrf And Ef-G., Nobuhiro Iwakura, Takeshi Yokoyama, Fabio Quaglia, Kaoru Mitsuoka, Kazuhiro Mio, Hideki Shigematsu, Mikako Shirouzu, Akira Kaji, Hideko Kaji

Department of Biochemistry and Molecular Biology Faculty Papers

A model Post-Termination Complex (PoTC) used for the discovery of Ribosome Recycling Factor (RRF) was purified and characterized by cryo-electron microscopic analysis and biochemical methods. We established that the model PoTC has mostly one tRNA, at the P/E or P/P position, together with one mRNA. The structural studies were supported by the biochemical measurement of bound tRNA and mRNA. Using this substrate, we establish that the release of tRNA, release of mRNA and splitting of ribosomal subunits occur during the recycling reaction. Order of these events is tRNA release first followed by mRNA release and splitting almost simultaneously. Moreover, we …

Structural And Functional Analysis Of A Β2-Adrenergic Receptor Complex With Grk5., Konstantin E. Komolov, Yang Du, Nguyen Minh Duc, Robin M. Betz, João P.G.L.M. Rodrigues, Ryan D. Leib, Dhabaleswar Patra, Georgios Skiniotis, Christopher M. Adams, Ron O. Dror, Ka Young Chung, Brian K. Kobilka, Jeffrey L. Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

The phosphorylation of agonist-occupied G-protein-coupled receptors (GPCRs) by GPCR kinases (GRKs) functions to turn off G-protein signaling and turn on arrestin-mediated signaling. While a structural understanding of GPCR/G-protein and GPCR/arrestin complexes has emerged in recent years, the molecular architecture of a GPCR/GRK complex remains poorly defined. We used a comprehensive integrated approach of cross-linking, hydrogen-deuterium exchange mass spectrometry (MS), electron microscopy, mutagenesis, molecular dynamics simulations, and computational docking to analyze GRK5 interaction with the β2-adrenergic receptor (β2AR). These studies revealed a dynamic mechanism of complex formation that involves large conformational changes in the GRK5 RH/catalytic domain interface upon receptor binding. …

A Genetically Encoded Fluorescent Trna Is Active In Live-Cell Protein Synthesis., Isao Masuda, Takao Igarashi, Reiko Sakaguchi, Ram G. Nitharwal, Ryuichi Takase, Kyu Young Han, Benjamin J. Leslie, Cuiping Liu, Howard Gamper, Taekjip Ha, Suparna Sanyal, Ya-Ming Hou

Department of Biochemistry and Molecular Biology Faculty Papers

Transfer RNAs (tRNAs) perform essential tasks for all living cells. They are major components of the ribosomal machinery for protein synthesis and they also serve in non-ribosomal pathways for regulation and signaling metabolism. We describe the development of a genetically encoded fluorescent tRNA fusion with the potential for imaging in live Escherichia coli cells. This tRNA fusion carries a Spinach aptamer that becomes fluorescent upon binding of a cell-permeable and non-toxic fluorophore. We show that, despite having a structural framework significantly larger than any natural tRNA species, this fusion is a viable probe for monitoring tRNA stability in a cellular …

G Protein-Coupled Receptor Kinase-2 (Grk-2) Regulates Serotonin Metabolism Through The Monoamine Oxidase Amx-2 In Caenorhabditis Elegans., Jianjun Wang, Jiansong Luo, Dipendra K. Aryal, William C. Wetsel, Richard Nass, Jeffrey L. Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

G protein-coupled receptors (GPCRs) regulate many animal behaviors. GPCR signaling is mediated by agonist-promoted interactions of GPCRs with heterotrimeric G proteins, GPCR kinases (GRKs), and arrestins. To further elucidate the role of GRKs in regulating GPCR-mediated behaviors, we utilized the genetic model system Caenorhabditis elegans Our studies demonstrate that grk-2 loss-of-function strains are egg laying-defective and contain low levels of serotonin (5-HT) and high levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA). The egg laying defect could be rescued by the expression of wild type but not by catalytically inactive grk-2 or by the selective expression of grk-2 in …

Cool-Associated Tyrosine-Phosphorylated Protein 1 Is Required For The Anchorage-Independent Growth Of Cervical Carcinoma Cells By Binding Paxillin And Promoting Akt Activation., Sungsoo M. Yoo, Arash Latifkar, Richard A. Cerione, Marc A. Antonyak

Department of Biochemistry and Molecular Biology Faculty Papers

Cool-associated tyrosine-phosphorylated protein 1 (Cat-1) is a signaling scaffold as well as an ADP-ribosylation factor-GTPase-activating protein. Although best known for its role in cell migration, we recently showed that the ability of Cat-1 to bind paxillin, a major constituent of focal complexes, is also essential for the anchorage-independent growth of HeLa cervical carcinoma cells. Here we set out to learn more about the underlying mechanism by which Cat-paxillin interactions mediate this effect. We show that knocking down paxillin expression in HeLa cells promotes their ability to form colonies in soft agar, whereas ectopically expressing paxillin in these cells inhibits this …

Portal Protein Functions Akin To A Dna-Sensor That Couples Genome-Packaging To Icosahedral Capsid Maturation., Ravi K. Lokareddy, Rajeshwer S. Sankhala, Ankoor Roy, Pavel V. Afonine, Tina Motwani, Carolyn M M. Teschke, Kristin N. Parent, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Tailed bacteriophages and herpesviruses assemble infectious particles via an empty precursor capsid (or 'procapsid') built by multiple copies of coat and scaffolding protein and by one dodecameric portal protein. Genome packaging triggers rearrangement of the coat protein and release of scaffolding protein, resulting in dramatic procapsid lattice expansion. Here, we provide structural evidence that the portal protein of the bacteriophage P22 exists in two distinct dodecameric conformations: an asymmetric assembly in the procapsid (PC-portal) that is competent for high affinity binding to the large terminase packaging protein, and a symmetric ring in the mature virion (MV-portal) that has negligible affinity …

Urokinase Plasminogen Activator Expression Is Regulated By P53 Harboring The Lung Cancer-Specific Mutation V157f, Julie Barta, Md, Kristen Pauley, Steven B. Mcmahon, Phd

Department of Biochemistry and Molecular Biology Posters

OBJECTIVES

• To define the mutant p53-regulated transcriptome of lung cancer cells with alterations at V157 and R158 in the p53 tumor suppressor.
• To determine the biological effects of lung-enriched p53 mutations in lung cancer cells.

Cleavage Of Dfna5 By Caspase-3 During Apoptosis Mediates Progression To Secondary Necrotic/Pyroptotic Cell Death., Corey Rogers, Teresa Fernandes-Alnemri, Lindsey Mayes, Diana Alnemri, Gino Cingolani, Emad S. Alnemri

Department of Biochemistry and Molecular Biology Faculty Papers

Apoptosis is a genetically regulated cell suicide programme mediated by activation of the effector caspases 3, 6 and 7. If apoptotic cells are not scavenged, they progress to a lytic and inflammatory phase called secondary necrosis. The mechanism by which this occurs is unknown. Here we show that caspase-3 cleaves the GSDMD-related protein DFNA5 after Asp270 to generate a necrotic DFNA5-N fragment that targets the plasma membrane to induce secondary necrosis/pyroptosis. Cells that express DFNA5 progress to secondary necrosis, when stimulated with apoptotic triggers such as etoposide or vesicular stomatitis virus infection, but disassemble into small apoptotic bodies when DFNA5 …