Medical Biochemistry Commons^™

Trna Methylation Is A Global Determinant Of Bacterial Multi-Drug Resistance., Isao Masuda, Ryuma Matsubara, Thomas Christian, Enrique R. Rojas, Srujana S. Yadavalli, Lisheng Zhang, Mark Goulian, Leonard J. Foster, Kerwyn Casey Huang, Ya-Ming Hou

Department of Biochemistry and Molecular Biology Faculty Papers

Gram-negative bacteria are intrinsically resistant to drugs because of their double-membrane envelope structure that acts as a permeability barrier and as an anchor for efflux pumps. Antibiotics are blocked and expelled from cells and cannot reach high-enough intracellular concentrations to exert a therapeutic effect. Efforts to target one membrane protein at a time have been ineffective. Here, we show that m ¹ G37-tRNA methylation determines the synthesis of a multitude of membrane proteins via its control of translation at proline codons near the start of open reading frames. Decreases in m ¹ G37 levels in Escherichia coli and Salmonella impair …

Gasdermin Pores Permeabilize Mitochondria To Augment Caspase-3 Activation During Apoptosis And Inflammasome Activation., Corey Rogers, Dan A. Erkes, Alexandria Nardone, Andrew E. Aplin, Teresa Fernandes-Alnemri, Emad S. Alnemri

Department of Biochemistry and Molecular Biology Faculty Papers

Gasdermin E (GSDME/DFNA5) cleavage by caspase-3 liberates the GSDME-N domain, which mediates pyroptosis by forming pores in the plasma membrane. Here we show that GSDME-N also permeabilizes the mitochondrial membrane, releasing cytochrome c and activating the apoptosome. Cytochrome c release and caspase-3 activation in response to intrinsic and extrinsic apoptotic stimuli are significantly reduced in GSDME-deficient cells comparing with wild type cells. GSDME deficiency also accelerates cell growth in culture and in a mouse model of melanoma. Phosphomimetic mutation of the highly conserved phosphorylatable Thr6 residue of GSDME, inhibits its pore-forming activity, thus uncovering a potential mechanism by which GSDME …

Loss-Of-Function Mutations In Lysyl-Trna Synthetase Cause Various Leukoencephalopathy Phenotypes, Chong Sun, Jie Song, Yanjun Jiang, Chongbo Zhao, Jiahong Lu, Yuxin Li, Yin Wang, Mingshi Gao, Jianying Xi, Sushan Luo, Meixia Li, Kevin Donaldson, Stephanie N. Oprescu, Thomas P. Slavin, Sansan Lee, Pilar L. Magoulas, Andrea M. Lewis, Lisa Emrick, Seema R. Lalani, Zhiyv Niu, Megan L. Landsverk, Magdalena Walkiewicz, Richard E. Person, Hui Mei, Jill A. Rosenfeld, Yaping Yang, Anthony Antonellis, Ya-Ming Hou, Jie Lin, Victor W. Zhang

Department of Biochemistry and Molecular Biology Faculty Papers

Objective: To expand the clinical spectrum of lysyl-tRNA synthetase (KARS) gene–related diseases, which so far includes Charcot-Marie-Tooth disease, congenital visual impairment and microcephaly, and nonsyndromic hearing impairment.

Methods: Whole-exome sequencing was performed on index patients from 4 unrelated families with leukoencephalopathy. Candidate pathogenic variants and their cosegregation were confirmed by Sanger sequencing. Effects of mutations on KARS protein function were examined by aminoacylation assays and yeast complementation assays.

Results: Common clinical features of the patients in this study included impaired cognitive ability, seizure, hypotonia, ataxia, and abnormal brain imaging, suggesting that the CNS involvement is the main …

Interaction Between The Bag1s Isoform And Hsp70 Mediates The Stability Of Anti-Apoptotic Proteins And The Survival Of Osteosarcoma Cells Expressing Oncogenic Myc., Victoria J. Gennaro, Helen Wedegaertner, Steven B. Mcmahon

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: The oncoprotein MYC has the dual capacity to drive cell cycle progression or induce apoptosis, depending on the cellular context. BAG1 was previously identified as a transcriptional target of MYC that functions as a critical determinant of this cell fate decision. The BAG1 protein is expressed as multiple isoforms, each having an array of distinct biochemical functions; however, the specific effector function of BAG1 that directs MYC-dependent cell survival has not been defined.

METHODS: In our studies the human osteosarcoma line U2OS expressing a conditional MYC-ER allele was used to induce oncogenic levels of MYC. We interrogated MYC-driven survival …

Impaired Nuclear Export Of Polyglutamine-Expanded Androgen Receptor In Spinal And Bulbar Muscular Atrophy., Frederick J. Arnold, Anna Pluciennik, Diane E. Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by polyglutamine (polyQ) expansion in the androgen receptor (AR). Prior studies have highlighted the importance of AR nuclear localization in SBMA pathogenesis; therefore, in this study, we sought to determine the role of AR nuclear export in the pathological manifestations of SBMA. We demonstrate here that the nuclear export of polyQ-expanded AR is impaired, even prior to the formation of intranuclear inclusions of aggregated AR. Additionally, we find that promoting AR export with an exogenous nuclear export signal substantially reduces its aggregation and blocks hormone-induced toxicity. Moreover, we show …

Codon-Specific Translation By M1g37 Methylation Of Trna, Ya-Ming Hou, Isao Masuda, Howard Gamper

Department of Biochemistry and Molecular Biology Faculty Papers

Although the genetic code is degenerate, synonymous codons for the same amino acid are not translated equally. Codon-specific translation is important for controlling gene expression and determining the proteome of a cell. At the molecular level, codon-specific translation is regulated by post-transcriptional epigenetic modifications of tRNA primarily at the wobble position 34 and at position 37 on the 3′-side of the anticodon. Modifications at these positions determine the quality of codon-anticodon pairing and the speed of translation on the ribosome. Different modifications operate in distinct mechanisms of codon-specific translation, generating a diversity of regulation that is previously unanticipated. Here we …

In Vitro Growth Of Human Ovarian Follicles For Fertility Preservation, Diego Marin, Min Yang, Tianren Wang

Department of Biochemistry and Molecular Biology Faculty Papers

Young female cancer survival rates significantly increased due to the great progress of cancer therapy. In fact, cryostorage and transplantation of ovarian tissue have already resulted in the birth of healthy babies. Follicle in vitro growth (IVG) has the great potential of restoring fertility by achieving functional oocytes from the most immature stages to maturation. This is suitable for a wide range of patients, from pubertal to perimenopause women. Notable achievements have been achieved in human follicle IVG in the past decade. Mature oocytes have been successfully collected from long-term sequential follicle IVG. However, it is still a major challenge …

Trypanosoma Brucei Prmt1 Is A Nucleic Acid Binding Protein With A Role In Energy Metabolism And The Starvation Stress Response., Lucie Kafková, Chengjian Tu, Kyle L. Pazzo, Kyle P. Smith, Erik W. Debler, Kimberly S. Paul, Jun Qu, Laurie K. Read

Department of Biochemistry and Molecular Biology Faculty Papers

In Trypanosoma brucei and related kinetoplastid parasites, transcription of protein coding genes is largely unregulated. Rather, mRNA binding proteins, which impact processes such as transcript stability and translation efficiency, are the predominant regulators of gene expression. Arginine methylation is a posttranslational modification that preferentially targets RNA binding proteins and is, therefore, likely to have a substantial impact on T. brucei biology. The data presented here demonstrate that cells depleted of T. brucei PRMT1 (TbPRMT1), a major type I protein arginine methyltransferase, exhibit decreased virulence in an animal model. To understand the basis of this phenotype, quantitative global proteomics was employed …

Highly Efficient 5' Capping Of Mitochondrial Rna With Nad+ And Nadh By Yeast And Human Mitochondrial Rna Polymerase, Jeremy G Bird, Urmimala Basu, David Kuster, Aparna Ramachandran, Ewa Grudzien-Nogalska, Atif Towheed, Douglas C. Wallace, Megerditch Kiledjian, Dmitry Temiakov, Smita S. Patel, Richard H. Ebright, Bryce E. Nickels

Department of Biochemistry and Molecular Biology Faculty Papers

Bacterial and eukaryotic nuclear RNA polymerases (RNAPs) cap RNA with the oxidized and reduced forms of the metabolic effector nicotinamide adenine dinucleotide, NAD+ and NADH, using NAD+ and NADH as non-canonical initiating nucleotides for transcription initiation. Here, we show that mitochondrial RNAPs (mtRNAPs) cap RNA with NAD+ and NADH, and do so more efficiently than nuclear RNAPs. Direct quantitation of NAD+- and NADH-capped RNA demonstrates remarkably high levels of capping in vivo: up to ~60% NAD+ and NADH capping of yeast mitochondrial transcripts, and up to ~15% NAD+ capping of human mitochondrial transcripts. The capping efficiency is determined by promoter …

Dna Methylation-Based Age Prediction And Telomere Length In White Blood Cells And Cumulus Cells Of Infertile Women With Normal Or Poor Response To Ovarian Stimulation., Scott J. Morin, Xin Tao, Diego Marin, Yiping Zhan, Jessica Landis, Jenna Bedard, Richard T. Scott, Emre Seli

Department of Biochemistry and Molecular Biology Faculty Papers

An algorithm assessing the methylation levels of 353 informative CpG sites in the human genome permits accurate prediction of the chronologic age of a subject. Interestingly, when there is discrepancy between the predicted age and chronologic age (age acceleration or "AgeAccel"), patients are at risk for morbidity and mortality. Identification of infertile patients at risk for accelerated reproductive senescence may permit preventative action. This study aimed to assess the accuracy of the "epigenetic clock" concept in reproductive age women undergoing fertility treatment by applying the age prediction algorithm in peripheral (white blood cells [WBCs]) and follicular somatic cells (cumulus cells …

Trna 3'-Amino-Tailing For Stable Amino Acid Attachment., Howard Gamper, Ya-Ming Hou

Department of Biochemistry and Molecular Biology Faculty Papers

Amino acids are attached to the tRNA 3'-end as a prerequisite for entering the ribosome for protein synthesis. Amino acid attachment also gives tRNA access to nonribosomal cellular activities. However, the normal attachment is via an ester linkage between the carboxylic group of the amino acid and the 3'-hydroxyl of the terminal A76 ribose in tRNA. The instability of this ester linkage has severely hampered studies of aminoacyl-tRNAs. Although the use of 3'-amino-3'-deoxy A76 in a 3'-amino-tailed tRNA provides stable aminoacyl attachment via an amide linkage, there are multiple tailing protocols and the efficiency of each relative to the others …

Control Of Ccnd1 Ubiquitylation By The Catalytic Saga Subunit Usp22 Is Essential For Cell Cycle Progression Through G1 In Cancer Cells., Victoria J. Gennaro, Timothy J. Stanek, Amy R. Peck, Yunguang Sun, Feng Wang, Shuo Qie, Karen E. Knudsen, Hallgeir Rui, Tauseef Butt, J. Alan Diehl, Steven B. Mcmahon

Department of Biochemistry and Molecular Biology Faculty Papers

Overexpression of the deubiquitylase ubiquitin-specific peptidase 22 (USP22) is a marker of aggressive cancer phenotypes like metastasis, therapy resistance, and poor survival. Functionally, this overexpression of USP22 actively contributes to tumorigenesis, as USP22 depletion blocks cancer cell cycle progression in vitro, and inhibits tumor progression in animal models of lung, breast, bladder, ovarian, and liver cancer, among others. Current models suggest that USP22 mediates these biological effects via its role in epigenetic regulation as a subunit of the Spt-Ada-Gcn5-acetyltransferase (SAGA) transcriptional cofactor complex. Challenging the dogma, we report here a nontranscriptional role for USP22 via a direct effect on the …

Pepducin-Mediated Cardioprotection Via Β-Arrestin-Biased Β2-Adrenergic Receptor-Specific Signaling, Laurel A. Grisanti, Toby P. Thomas, Rhonda L. Carter, Claudio De Lucia, Erhe Gao, Walter J. Koch, Jeffrey L. Benovic, Douglas G. Tilley

Department of Biochemistry and Molecular Biology Faculty Papers

Reperfusion as a therapeutic intervention for acute myocardial infarction-induced cardiac injury itself induces further cardiomyocyte death. β-arrestin (βarr)-biased β-adrenergic receptor (βAR) activation promotes survival signaling responses in vitro; thus, we hypothesize that this pathway can mitigate cardiomyocyte death at the time of reperfusion to better preserve function. However, a lack of efficacious βarr-biased orthosteric small molecules has prevented investigation into whether this pathway relays protection against ischemic injury in vivo. We recently demonstrated that the pepducin ICL1-9, a small lipidated peptide fragment designed from the first intracellular loop of β2AR, allosterically engaged pro-survival signaling cascades in a βarr-dependent manner in …

Structural Basis Of Mitochondrial Transcription., Hauke S. Hillen, Dmitry Temiakov, Patrick Cramer

Department of Biochemistry and Molecular Biology Faculty Papers

The mitochondrial genome is transcribed by a single-subunit DNA-dependent RNA polymerase (mtRNAP) and its auxiliary factors. Structural studies have elucidated how mtRNAP cooperates with its dedicated transcription factors to direct RNA synthesis: initiation factors TFAM and TFB2M assist in promoter-DNA binding and opening by mtRNAP while the elongation factor TEFM increases polymerase processivity to the levels required for synthesis of long polycistronic mtRNA transcripts. Here, we review the emerging body of structural and functional studies of human mitochondrial transcription, provide a molecular movie that can be used for teaching purposes and discuss the open questions to guide future directions of …

Coupling Of Smoothened To Inhibitory G Proteins Reduces Voltage-Gated K, Lan Cheng, Moza Al-Owais, Manuel Covarrubias, Walter J. Koch, David R. Manning, Chris Peers, Natalia A Riobo-Del Galdo

Department of Biochemistry and Molecular Biology Faculty Papers

SMO (Smoothened), the central transducer of Hedgehog signaling, is coupled to heterotrimeric G_i proteins in many cell types, including cardiomyocytes. In this study, we report that activation of SMO with SHH (Sonic Hedgehog) or a small agonist, purmorphamine, rapidly causes a prolongation of the action potential duration that is sensitive to a SMO inhibitor. In contrast, neither of the SMO agonists prolonged the action potential in cardiomyocytes from transgenic G_iCT/TTA mice, in which G_i signaling is impaired, suggesting that the effect of SMO is mediated by G_i proteins. Investigation of the mechanism underlying the change …

Triad3a Induces The Degradation Of Early Necrosome To Limit Ripk1-Dependent Cytokine Production And Necroptosis., Norah A. Alturki, Scott Mccomb, Ardeshir Ariana, Dikchha Rijal, Robert G. Korneluk, Shao-Cong Sun, Emad S Alnemri, Subash Sad

Department of Biochemistry and Molecular Biology Faculty Papers

Understanding the molecular signaling in programmed cell death is vital to a practical understanding of inflammation and immune cell function. Here we identify a previously unrecognized mechanism that functions to downregulate the necrosome, a central signaling complex involved in inflammation and necroptosis. We show that RipK1 associates with RipK3 in an early necrosome, independent of RipK3 phosphorylation and MLKL-induced necroptotic death. We find that formation of the early necrosome activates K48-ubiquitin-dependent proteasomal degradation of RipK1, Caspase-8, and other necrosomal proteins. Our results reveal that the E3-ubiquitin ligase Triad3a promotes this negative feedback loop independently of typical RipK1 ubiquitin editing enzymes, …

The Mitochondrial Protease Htra2 Restricts The Nlrp3 And Aim2 Inflammasomes., Ian Gaël Rodrigue-Gervais, Karine Doiron, Claudia Champagne, Lindsey Mayes, Gabriel André Leiva-Torres, Paulin Vanié, Todd Douglas, Silvia M. Vidal, Emad S. Alnemri, Maya Saleh

Department of Biochemistry and Molecular Biology Faculty Papers

Activation of the inflammasome pathway is crucial for effective intracellular host defense. The mitochondrial network plays an important role in inflammasome regulation but the mechanisms linking mitochondrial homeostasis to attenuation of inflammasome activation are not fully understood. Here, we report that the Parkinson's disease-associated mitochondrial serine protease HtrA2 restricts the activation of ASC-dependent NLRP3 and AIM2 inflammasomes, in a protease activity-dependent manner. Consistently, disruption of the protease activity of HtrA2 results in exacerbated NLRP3 and AIM2 inflammasome responses in macrophages ex vivo and systemically in vivo. Mechanistically, we show that the HtrA2 protease activity regulates autophagy and controls the magnitude …

Breaking Symmetry In Viral Icosahedral Capsids As Seen Through The Lenses Of X-Ray Crystallography And Cryo-Electron Microscopy., Kristin N. Parent, Jason R. Schrad, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

The majority of viruses on Earth form capsids built by multiple copies of one or more types of a coat protein arranged with 532 symmetry, generating an icosahedral shell. This highly repetitive structure is ideal to closely pack identical protein subunits and to enclose the nucleic acid genomes. However, the icosahedral capsid is not merely a passive cage but undergoes dynamic events to promote packaging, maturation and the transfer of the viral genome into the host. These essential processes are often mediated by proteinaceous complexes that interrupt the shell's icosahedral symmetry, providing a gateway through the capsid. In this review, …

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 …

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 …

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 …

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 …