Medical Biochemistry Commons^™

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 …

Tp53-Inducible Glycolysis And Apoptosis Regulator (Tigar) Metabolically Reprograms Carcinoma And Stromal Cells In Breast Cancer., Ying-Hui Ko, Marina Domingo-Vidal, Megan Roche, Zhao Lin, Diana Whitaker-Menezes, Erin Seifert, Claudia Capparelli, Madalina Tuluc, Ruth C. Birbe, Patrick Tassone, Joseph M. Curry, Àurea Navarro-Sabaté, Anna Manzano, Ramon Bartrons, Jaime Caro, Ubaldo E. Martinez-Outshoorn

Department of Medical Oncology Faculty Papers

A subgroup of breast cancers has several metabolic compartments. The mechanisms by which metabolic compartmentalization develop in tumors are poorly characterized. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a bisphosphatase that reduces glycolysis and is highly expressed in carcinoma cells in the majority of human breast cancers. Hence we set out to determine the effects of TIGAR expression on breast carcinoma and fibroblast glycolytic phenotype and tumor growth. The overexpression of this bisphosphatase in carcinoma cells induces expression of enzymes and transporters involved in the catabolism of lactate and glutamine. Carcinoma cells overexpressing TIGAR have higher oxygen consumption rates …

Natural And Induced Mitochondrial Phosphate Carrier Loss: Differential Dependence Of Mitochondrial Metabolism And Dynamics And Cell Survival On The Extent Of Depletion., Erin L. Seifert, Aniko Gál, Michelle G. Acoba, Qipei Li, Lauren Anderson-Pullinger, Tünde Golenár, Cynthia Moffat, Neal Sondheimer, Steven M. Claypool, György Hajnóczky

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

The relevance of mitochondrial phosphate carrier (PiC), encoded by SLC25A3, in bioenergetics is well accepted. However, little is known about the mechanisms mediating the cellular impairments induced by pathological SLC25A3 variants. To this end, we investigated the pathogenicity of a novel compound heterozygous mutation in SLC25A3 First, each variant was modeled in yeast, revealing that substituting GSSAS for QIP within the fifth matrix loop is incompatible with survival on non-fermentable substrate, whereas the L200W variant is functionally neutral. Next, using skin fibroblasts from an individual expressing these variants and HeLa cells with varying degrees of PiC depletion, PiC loss of …

The Yersinia Pestis Effector Yopm Inhibits Pyrin Inflammasome Activation., Dmitry Ratner, M Pontus A Orning, Megan K. Proulx, Donghai Wang, Mikhail A. Gavrilin, Mark D. Wewers, Emad S. Alnemri, Peter F. Johnson, Bettina Lee, Joan Mecsas, Nobuhiko Kayagaki, Jon D. Goguen, Egil Lien

Department of Biochemistry and Molecular Biology Faculty Papers

Type III secretion systems (T3SS) are central virulence factors for many pathogenic Gram-negative bacteria, and secreted T3SS effectors can block key aspects of host cell signaling. To counter this, innate immune responses can also sense some T3SS components to initiate anti-bacterial mechanisms. The Yersinia pestis T3SS is particularly effective and sophisticated in manipulating the production of pro-inflammatory cytokines IL-1β and IL-18, which are typically processed into their mature forms by active caspase-1 following inflammasome formation. Some effectors, like Y. pestis YopM, may block inflammasome activation. Here we show that YopM prevents Y. pestis induced activation of the Pyrin inflammasome induced …

Palmitoylation Of Desmoglein 2 Is A Regulator Of Assembly Dynamics And Protein Turnover., Brett J. Roberts, Robert A. Svoboda, Andrew M. Overmiller, Joshua D. Lewis, Andrew P. Kowalczyk, My G. Mahoney, Keith R. Johnson, James K. Wahl

Department of Dermatology and Cutaneous Biology Faculty Papers

Desmosomes are prominent adhesive junctions present between many epithelial cells as well as cardiomyocytes. The mechanisms controlling desmosome assembly and remodeling in epithelial and cardiac tissue are poorly understood. We recently identified protein palmitoylation as a mechanism regulating desmosome dynamics. In this study, we have focused on the palmitoylation of the desmosomal cadherin desmoglein-2 (Dsg2) and characterized the role that palmitoylation of Dsg2 plays in its localization and stability in cultured cells. We identified two cysteine residues in the juxtamembrane (intracellular anchor) domain of Dsg2 that, when mutated, eliminate its palmitoylation. These cysteine residues are conserved in all four desmoglein …

The Α-Arrestin Arrdc3 Regulates The Endosomal Residence Time And Intracellular Signaling Of The Β2-Adrenergic Receptor., Xufan Tian, Roshanak Irannejad, Shanna L. Bowman, Yang Du, Manojkumar A. Puthenveedu, Mark Von Zastrow, Jeffrey L. Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

Arrestin domain-containing protein 3 (ARRDC3) is a member of the mammalian α-arrestin family, which is predicted to share similar tertiary structure with visual-/β-arrestins and also contains C-terminal PPXY motifs that mediate interaction with E3 ubiquitin ligases. Recently, ARRDC3 has been proposed to play a role in regulating the trafficking of G protein-coupled receptors, although mechanistic insight into this process is lacking. Here, we focused on characterizing the role of ARRDC3 in regulating the trafficking of the β2-adrenergic receptor (β2AR). We find that ARRDC3 primarily localizes to EEA1-positive early endosomes and directly interacts with the β2AR in a ligand-independent manner. Although …

Molecular Basis And Consequences Of The Cytochrome C-Trna Interaction., Cuiping Liu, Aaron J Stonestrom, Thomas Christian, Jeongsik Yong, Ryuichi Takase, Ya-Ming Hou, Xiaolu Yang

Department of Biochemistry and Molecular Biology Faculty Papers

The intrinsic apoptosis pathway occurs through the release of mitochondrial cytochrome c to the cytosol, where it promotes activation of the caspase family of proteases. The observation that tRNA binds to cytochrome c revealed a previously unexpected mode of apoptotic regulation. However, the molecular characteristics of this interaction, and its impact on each interaction partner, are not well understood. Using a novel fluorescence assay, we show here that cytochrome c binds to tRNA with an affinity comparable with other tRNA-protein binding interactions and with a molecular ratio of ∼3:1. Cytochrome c recognizes the tertiary structural features of tRNA, particularly in …

A Parp1-Erk2 Synergism Is Required For The Induction Of Ltp., L Visochek, G Grigoryan, A Kalal, H Milshtein-Parush, N Gazit, I Slutsky, A Yeheskel, A Shainberg, A Castiel, R Seger, Marie-France Langelier, F Dantzer, Pascal Jabbour Md, M Segal, M Cohen-Armon

Department of Biochemistry and Molecular Biology Faculty Papers

Unexpectedly, a post-translational modification of DNA-binding proteins, initiating the cell response to single-strand DNA damage, was also required for long-term memory acquisition in a variety of learning paradigms. Our findings disclose a molecular mechanism based on PARP1-Erk synergism, which may underlie this phenomenon. A stimulation induced PARP1 binding to phosphorylated Erk2 in the chromatin of cerebral neurons caused Erk-induced PARP1 activation, rendering transcription factors and promoters of immediate early genes (IEG) accessible to PARP1-bound phosphorylated Erk2. Thus, Erk-induced PARP1 activation mediated IEG expression implicated in long-term memory. PARP1 inhibition, silencing, or genetic deletion abrogated stimulation-induced Erk-recruitment to IEG promoters, gene …

Bonded Cumomer Analysis Of Human Melanoma Metabolism Monitored By 13c Nmr Spectroscopy Of Perfused Tumor Cells., Alexander A Shestov, Anthony Mancuso, Seung-Cheol Lee, Lili Guo, David S Nelson, Jeffrey C Roman, Pierre-Gilles Henry, Dennis B. Leeper, Ian A Blair, Jerry D Glickson

Department of Radiation Oncology Faculty Papers

A network model for the determination of tumor metabolic fluxes from (13)C NMR kinetic isotopomer data has been developed and validated with perfused human DB-1 melanoma cells carrying the BRAF V600E mutation, which promotes oxidative metabolism. The model generated in the bonded cumomer formalism describes key pathways of tumor intermediary metabolism and yields dynamic curves for positional isotopic enrichment and spin-spin multiplets. Cells attached to microcarrier beads were perfused with 26 mm [1,6-(13)C2]glucose under normoxic conditions at 37 °C and monitored by (13)C NMR spectroscopy. Excellent agreement between model-predicted and experimentally measured values of the rates of oxygen and glucose …

The Eff-1a Cytoplasmic Domain Influences Hypodermal Cell Fusions In C. Elegans But Is Not Dependent On 14-3-3 Proteins., Jessica H Shinn-Thomas, Jacob J Del Campo, Jianjun Wang, William A Mohler

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: Regulatory and biophysical mechanisms of cell-cell fusion are largely unknown despite the fundamental requirement for fused cells in eukaryotic development. Only two cellular fusogens that are not of clear recent viral origin have been identified to date, both in nematodes. One of these, EFF-1, is necessary for most cell fusions in Caenorhabditis elegans. Unregulated EFF-1 expression causes lethality due to ectopic fusion between cells not developmentally programmed to fuse, highlighting the necessity of tight fusogen regulation for proper development. Identifying factors that regulate EFF-1 and its paralog AFF-1 could lead to discovery of molecular mechanisms that control cell fusion …

Autophosphorylation Of The Smk1 Mapk Is Spatially And Temporally Regulated By Ssp2 During Meiotic Development In Yeast., Chong Wai Tio, Gregory Omerza, Sham Sunder, Edward Winter

Department of Biochemistry and Molecular Biology Faculty Papers

Smk1 is a meiosis-specific MAPK that controls spore wall morphogenesis in Saccharomyces cerevisiae. Although Smk1 is activated by phosphorylation of the threonine (T) and tyrosine (Y) in its activation loop, it is not phosphorylated by a dual-specificity MAPK kinase. Instead, the T is phosphorylated by the cyclin-dependent kinase (CDK)-activating kinase, Cak1. The Y is autophosphorylated in an intramolecular reaction that requires a meiosis-specific protein named Ssp2. The meiosis-specific CDK-like kinase, Ime2, was previously shown to positively regulate Smk1. Here we show that Ime2 activity is required to induce the translation of SSP2 mRNA at anaphase II. Ssp2 protein is then …

Atomic Structure Of Grk5 Reveals Distinct Structural Features Novel For G Protein-Coupled Receptor Kinases, Konstantin E. Komolov, Anshul Bhardwaj, Jeffrey L. Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

G protein-coupled receptor kinases (GRKs) are members of the protein kinase A, G, and C families (AGC) and play a central role in mediating G protein-coupled receptor phosphorylation and desensitization. One member of the family, GRK5, has been implicated in several human pathologies, including heart failure, hypertension, cancer, diabetes, and Alzheimer disease. To gain mechanistic insight into GRK5 function, we determined a crystal structure of full-length human GRK5 at 1.8 Å resolution. GRK5 in complex with the ATP analog 5'-adenylyl β,γ-imidodiphosphate or the nucleoside sangivamycin crystallized as a monomer. The C-terminal tail (C-tail) of AGC kinase domains is a highly …

The Rise And Fall Of Poly(Adp-Ribose): An Enzymatic Perspective., John M. Pascal, Tom Ellenberger

Department of Biochemistry and Molecular Biology Faculty Papers

Human cells respond to DNA damage with an acute and transient burst in production of poly(ADP-ribose), a posttranslational modification that expedites damage repair and plays a pivotal role in cell fate decisions. Poly(ADP-ribose) polymerases (PARPs) and glycohydrolase (PARG) are the key set of enzymes that orchestrate the rise and fall in cellular levels of poly(ADP-ribose). In this perspective, we focus on recent structural and mechanistic insights into the enzymes involved in poly(ADP-ribose) production and turnover, and we highlight important questions that remain to be answered.

Sex Hormone-Dependent Trna Halves Enhance Cell Proliferation In Breast And Prostate Cancers., Shozo Honda, Phillipe Loher, Megumi Shigematsu, Juan P. Palazzo, Ryusuke Suzuki, Issei Imoto, Isidore Rigoutsos, Yohei Kirino, Phd

Computational Medicine Center Faculty Papers

Sex hormones and their receptors play critical roles in the development and progression of the breast and prostate cancers. Here we report that a novel type of transfer RNA (tRNA)-derived small RNA, termed Sex HOrmone-dependent TRNA-derived RNAs (SHOT-RNAs), are specifically and abundantly expressed in estrogen receptor (ER)-positive breast cancer and androgen receptor (AR)-positive prostate cancer cell lines. SHOT-RNAs are not abundantly present in ER(-) breast cancer, AR(-) prostate cancer, or other examined cancer cell lines from other tissues. ER-dependent accumulation of SHOT-RNAs is not limited to a cell culture system, but it also occurs in luminal-type breast cancer patient tissues. …

Diversification Of Importin-Α Isoforms In Cellular Trafficking And Disease States., Ruth A. Pumroy, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

The human genome encodes seven isoforms of importin α which are grouped into three subfamilies known as α1, α2 and α3. All isoforms share a fundamentally conserved architecture that consists of an N-terminal, autoinhibitory, importin-β-binding (IBB) domain and a C-terminal Arm (Armadillo)-core that associates with nuclear localization signal (NLS) cargoes. Despite striking similarity in amino acid sequence and 3D structure, importin-α isoforms display remarkable substrate specificity in vivo. In the present review, we look at key differences among importin-α isoforms and provide a comprehensive inventory of known viral and cellular cargoes that have been shown to associate preferentially with specific …

Disrupting Sumoylation Enhances Transcriptional Function And Ameliorates Polyglutamine Androgen Receptor-Mediated Disease., Jason P Chua, Satya L Reddy, Zhigang Yu, Elisa Giorgetti, Heather L Montie, Sarmistha Mukherjee, Jake Higgins, Richard C Mceachin, Diane M Robins, Diane E Merry, Jorge A Iñiguez-Lluhí, Andrew P Lieberman

Department of Biochemistry and Molecular Biology Faculty Papers

Expansion of the polyglutamine (polyQ) tract within the androgen receptor (AR) causes neuromuscular degeneration in individuals with spinobulbar muscular atrophy (SBMA). PolyQ AR has diminished transcriptional function and exhibits ligand-dependent proteotoxicity, features that have both been implicated in SBMA; however, the extent to which altered AR transcriptional function contributes to pathogenesis remains controversial. Here, we sought to dissociate effects of diminished AR function from polyQ-mediated proteotoxicity by enhancing the transcriptional activity of polyQ AR. To accomplish this, we bypassed the inhibitory effect of AR SUMOylation (where SUMO indicates small ubiquitin-like modifier) by mutating conserved lysines in the polyQ AR that …

Isoform- And Species-Specific Control Of Inositol 1,4,5-Trisphosphate (Ip3) Receptors By Reactive Oxygen Species., Száva Bánsághi, Tünde Golenár, Muniswamy Madesh, György Csordás, Satish P. Ramachandrarao, Kumar Sharma, David I Yule, Suresh K Joseph, György Hajnóczky

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Reactive oxygen species (ROS) stimulate cytoplasmic [Ca(2+)] ([Ca(2+)]c) signaling, but the exact role of the IP3 receptors (IP3R) in this process remains unclear. IP3Rs serve as a potential target of ROS produced by both ER and mitochondrial enzymes, which might locally expose IP3Rs at the ER-mitochondrial associations. Also, IP3Rs contain multiple reactive thiols, common molecular targets of ROS. Therefore, we have examined the effect of superoxide anion (O2) on IP3R-mediated Ca(2+) signaling. In human HepG2, rat RBL-2H3, and chicken DT40 cells, we observed [Ca(2+)]c spikes and frequency-modulated oscillations evoked by a O2 donor, xanthine (X) + xanthine oxidase (XO), dose-dependently. …

Exploring The Atomic Structure And Conformational Flexibility Of A 320 Å Long Engineered Viral Fiber Using X-Ray Crystallography., Anshul Bhardwaj, Sherwood R Casjens, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Protein fibers are widespread in nature, but only a limited number of high-resolution structures have been determined experimentally. Unlike globular proteins, fibers are usually recalcitrant to form three-dimensional crystals, preventing single-crystal X-ray diffraction analysis. In the absence of three-dimensional crystals, X-ray fiber diffraction is a powerful tool to determine the internal symmetry of a fiber, but it rarely yields atomic resolution structural information on complex protein fibers. An 85-residue-long minimal coiled-coil repeat unit (MiCRU) was previously identified in the trimeric helical core of tail needle gp26, a fibrous protein emanating from the tail apparatus of the bacteriophage P22 virion. Here, …

Scavenger Receptor Class B Type I Regulates Cellular Cholesterol Metabolism And Cell Signaling Associated With Breast Cancer Development., Christiane Danilo, Jorge L Gutierrez-Pajares, Maria Antonietta Mainieri, Isabelle Mercier, Michael P. Lisanti, Philippe G. Frank

Department of Stem Cell Biology and Regenerative Medicine Faculty Papers & Presentations

INTRODUCTION: Previous studies have identified cholesterol as an important regulator of breast cancer development. High-density lipoprotein (HDL) and its cellular receptor, scavenger receptor class B type I (SR-BI) have both been implicated in the regulation of cellular cholesterol homeostasis, but their functions in cancer remain to be established.

METHODS: In the present study, we have examined the role of HDL and SR-BI in the regulation of cellular signaling pathways in breast cancer cell lines and in the development of tumor in a mouse xenograft model.

RESULTS: Our data show that HDL is capable of stimulating migration and can activate signal …

Possible Steps Of Complete Disassembly Of Post-Termination Complex By Yeast Eef3 Deduced From Inhibition By Translocation Inhibitors., Shinya Kurata, Ben Shen, Jun O Liu, Nono Takeuchi, Akira Kaji, Hideko Kaji

Department of Biochemistry and Molecular Biology Faculty Papers

Ribosomes, after one round of translation, must be recycled so that the next round of translation can occur. Complete disassembly of post-termination ribosomal complex (PoTC) in yeast for the recycling consists of three reactions: release of tRNA, release of mRNA and splitting of ribosomes, catalyzed by eukaryotic elongation factor 3 (eEF3) and ATP. Here, we show that translocation inhibitors cycloheximide and lactimidomycin inhibited all three reactions. Cycloheximide is a non-competitive inhibitor of both eEF3 and ATP. The inhibition was observed regardless of the way PoTC was prepared with either release factors or puromycin. Paromomycin not only inhibited all three reactions …

Dynein And Dynactin Leverage Their Bivalent Character To Form A High-Affinity Interaction., Amanda E Siglin, Shangjin Sun, Jeffrey K Moore, Sarah Tan, Martin Poenie, James D Lear, Tatyana Polenova, John A Cooper, John C Williams

Department of Biochemistry and Molecular Biology Faculty Papers

Cytoplasmic dynein and dynactin participate in retrograde transport of organelles, checkpoint signaling and cell division. The principal subunits that mediate this interaction are the dynein intermediate chain (IC) and the dynactin p150(Glued); however, the interface and mechanism that regulates this interaction remains poorly defined. Herein, we use multiple methods to show the N-terminus of mammalian dynein IC, residues 10-44, is sufficient for binding p150(Glued). Consistent with this mapping, monoclonal antibodies that antagonize the dynein-dynactin interaction also bind to this region of the IC. Furthermore, double and triple alanine point mutations spanning residues 6 to 19 in the yeast IC homolog, …

Molecular Determinants Of Epidermal Growth Factor Binding: A Molecular Dynamics Study., Jeffrey M Sanders, Matthew E Wampole, Mathew L. Thakur, Eric Wickstrom

Department of Biochemistry and Molecular Biology Faculty Papers

The epidermal growth factor receptor (EGFR) is a member of the receptor tyrosine kinase family that plays a role in multiple cellular processes. Activation of EGFR requires binding of a ligand on the extracellular domain to promote conformational changes leading to dimerization and transphosphorylation of intracellular kinase domains. Seven ligands are known to bind EGFR with affinities ranging from sub-nanomolar to near micromolar dissociation constants. In the case of EGFR, distinct conformational states assumed upon binding a ligand is thought to be a determining factor in activation of a downstream signaling network. Previous biochemical studies suggest the existence of both …

The Tip Of The Tail Needle Affects The Rate Of Dna Delivery By Bacteriophage P22., Justin C Leavitt, Lasha Gogokhia, Eddie B Gilcrease, Anshul Bhardwaj, Gino Cingolani, Sherwood R Casjens

Department of Biochemistry and Molecular Biology Faculty Papers

The P22-like bacteriophages have short tails. Their virions bind to their polysaccharide receptors through six trimeric tailspike proteins that surround the tail tip. These short tails also have a trimeric needle protein that extends beyond the tailspikes from the center of the tail tip, in a position that suggests that it should make first contact with the host's outer membrane during the infection process. The base of the needle serves as a plug that keeps the DNA in the virion, but role of the needle during adsorption and DNA injection is not well understood. Among the P22-like phages are needle …

Structural Implications For Selective Targeting Of Parps., Jamin D Steffen, Md, Jonathan Brody, Md, Roger S Armen, Md, John M Pascal, Md

Department of Biochemistry and Molecular Biology Faculty Papers

Poly(ADP-ribose) polymerases (PARPs) are a family of enzymes that use NAD(+) as a substrate to synthesize polymers of ADP-ribose (PAR) as post-translational modifications of proteins. PARPs have important cellular roles that include preserving genomic integrity, telomere maintenance, transcriptional regulation, and cell fate determination. The diverse biological roles of PARPs have made them attractive therapeutic targets, which have fueled the pursuit of small molecule PARP inhibitors. The design of PARP inhibitors has matured over the past several years resulting in several lead candidates in clinical trials. PARP inhibitors are mainly used in clinical trials to treat cancer, particularly as sensitizing agents …

Possible Steps Of Complete Disassembly Of Post-Termination Complex By Yeast Eef3 Deduced From Inhibition By Translocation Inhibitors., Shinya Kurata, Ben Shen, Jun O Liu, Nono Takeuchi, Akira Kaji, Hideko Kaji

Department of Biochemistry and Molecular Biology Faculty Papers

Ribosomes, after one round of translation, must be recycled so that the next round of translation can occur. Complete disassembly of post-termination ribosomal complex (PoTC) in yeast for the recycling consists of three reactions: release of tRNA, release of mRNA and splitting of ribosomes, catalyzed by eukaryotic elongation factor 3 (eEF3) and ATP. Here, we show that translocation inhibitors cycloheximide and lactimidomycin inhibited all three reactions. Cycloheximide is a non-competitive inhibitor of both eEF3 and ATP. The inhibition was observed regardless of the way PoTC was prepared with either release factors or puromycin. Paromomycin not only inhibited all three reactions …

Global Cellular Regulation Including Cardiac Function By Post-Translational Protein Arginylation., Hideko Kaji, Akira Kaji

Department of Biochemistry and Molecular Biology Faculty Papers

In this issue a very significant contribution to cardiology describing critical roles of ATE1 appears by Kurosaka et al. [1]. In view of this paper, as the discoverers of ATE1, we have been asked to contribute an article (editorial) regarding ATE1 (enzyme which transfers arginine from arginyl tRNA to protein acceptors). This short article consists of three sections: 1) a historical anecdote describing how ATE1 was discovered; 2) its possible role in aging and cellular transformation, and most importantly; 3) its role in the development and maintenance of cardiac activity. The last section has direct bearing to the Kurosaka …

Engrailed Cooperates Directly With Extradenticle And Homothorax On A Distinct Class Of Homeodomain Binding Sites To Repress Sloppy Paired., Miki Fujioka, Brian Gebelein, Zenobia C Cofer, Richard S Mann, James B Jaynes

Department of Biochemistry and Molecular Biology Faculty Papers

Even skipped (Eve) and Engrailed (En) are homeodomain-containing transcriptional repressors with similar DNA binding specificities that are sequentially expressed in Drosophila embryos. The sloppy-paired (slp) locus is a target of repression by both Eve and En. At blastoderm, Eve is expressed in 7 stripes that restrict the posterior border of slp stripes, allowing engrailed (en) gene expression to be initiated in odd-numbered parasegments. En, in turn, prevents expansion of slp stripes after Eve is turned off. Prior studies showed that the two tandem slp transcription units are regulated by cis-regulatory modules (CRMs) with activities that overlap in space and time. …

Protein Synthesis Factors (Rf1, Rf2, Rf3, Rrf, And Tmrna) And Peptidyl-Trna Hydrolase Rescue Stalled Ribosomes At Sense Codons., Serafín Vivanco-Domínguez, José Bueno-Martínez, Gloria León-Avila, Nobuhiro Iwakura, Akira Kaji, Hideko Kaji, Gabriel Guarneros

Department of Biochemistry and Molecular Biology Faculty Papers

During translation, ribosomes stall on mRNA when the aminoacyl-tRNA to be read is not readily available. The stalled ribosomes are deleterious to the cell and should be rescued to maintain its viability. To investigate the contribution of some of the cellular translation factors on ribosome rescuing, we provoked stalling at AGA codons in mutants that affected the factors and then analyzed the accumulation of oligopeptidyl (peptides of up to 6 amino acid residues, oligopep-)-tRNA or polypeptidyl (peptides of more than 300 amino acids in length, polypep-)-tRNA associated with ribosomes. Stalling was achieved by starvation for aminoacyl-tRNA(Arg4) upon induced expression of …