FUS contributes to mTOR-dependent inhibition of translation [Signal Transduction]
The amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD)–linked RNA-binding protein called FUS (fused in sarcoma) has been implicated in several aspects of RNA regulation, including mRNA translation. The mechanism by which FUS affects the translation of polyribosomes has not been established. Here we show that FUS can associate with stalled polyribosomes and that this association is sensitive to mTOR (mammalian target of rapamycin) kinase activity. Specifically, we show that FUS association with polyribosomes is increased by Torin1 treatment or when cells are cultured in nutrient-deficient media, but not...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Myriam Sevigny, Isabelle Bourdeau Julien, Janani Priya Venkatasubramani, Jeremy B. Hui, Paul A. Dutchak, Chantelle F. Sephton Tags: Molecular Bases of Disease Source Type: research
Determinants of replication protein A subunit interactions revealed using a phosphomimetic peptide [Molecular Biophysics]
In this study, we provide molecular details of the interaction between RPA70 and a mimic of phosphorylated RPA32 (pmRPA32) using fluorescence polarization and NMR analysis. We show that the N-terminal domain of RPA70 (RPA70N) specifically participates in pmRPA32 binding, whereas the unphosphorylated RPA32 does not bind to RPA70N. Our NMR data revealed that RPA70N binds pmRPA32 using a basic cleft region. We also show that at least 6 negatively charged residues of pmRPA32 are required for RPA70N binding. By introducing alanine mutations into hydrophobic positions of pmRPA32, we found potential points of contact between RPA7...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Sungjin Lee, Jeongbeen Heo, Chin-Ju Park Tags: Protein Structure and Folding Source Type: research
Development of a novel mammalian display system for selection of antibodies against membrane proteins [Immunology]
Reliable, specific polyclonal and monoclonal antibodies are important tools in research and medicine. However, the discovery of antibodies against their targets in their native forms is difficult. Here, we present a novel method for discovery of antibodies against membrane proteins in their native configuration in mammalian cells. The method involves the co-expression of an antibody library in a population of mammalian cells that express the target polypeptide within a natural membrane environment on the cell surface. Cells that secrete a single-chain fragment variable (scFv) that binds to the target membrane protein there...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Nathan Robertson, Nancy Lopez-Anton, Shalom A. Gurjar, Hena Khalique, Zainab Khalaf, Siobhan Clerkin, Vaughan R. Leydon, Richard Parker-Manuel, Alexander Raeside, Tom Payne, Tim D. Jones, Len Seymour, Ryan Cawood Tags: Methods and Resources Source Type: research
The structure of a family 110 glycoside hydrolase provides insight into the hydrolysis of {alpha}-1,3-galactosidic linkages in {lambda}-carrageenan and blood group antigens [Enzymology]
α-Linked galactose is a common carbohydrate motif in nature that is processed by a variety of glycoside hydrolases from different families. Terminal Galα1–3Gal motifs are found as a defining feature of different blood group and tissue antigens, as well as the building block of the marine algal galactan λ-carrageenan. The blood group B antigen and linear α-Gal epitope can be processed by glycoside hydrolases in family GH110, whereas the presence of genes encoding GH110 enzymes in polysaccharide utilization loci from marine bacteria suggests a role in processing λ-carrageenan. However, the structure–function relatio...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Bailey E. McGuire, Andrew G. Hettle, Chelsea Vickers, Dustin T. King, David J. Vocadlo, Alisdair B. Boraston Tags: Glycobiology and Extracellular Matrices Source Type: research
Structure, mechanism, and regulation of mitochondrial DNA transcription initiation [Enzymology]
Mitochondria are specialized compartments that produce requisite ATP to fuel cellular functions and serve as centers of metabolite processing, cellular signaling, and apoptosis. To accomplish these roles, mitochondria rely on the genetic information in their small genome (mitochondrial DNA) and the nucleus. A growing appreciation for mitochondria's role in a myriad of human diseases, including inherited genetic disorders, degenerative diseases, inflammation, and cancer, has fueled the study of biochemical mechanisms that control mitochondrial function. The mitochondrial transcriptional machinery is different from nuclear m...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Urmimala Basu, Alicia M. Bostwick, Kalyan Das, Kristin E. Dittenhafer-Reed, Smita S. Patel Tags: JBC Reviews Source Type: research
Methylated PP2A stabilizes Gcn4 to enable a methionine-induced anabolic program [Metabolism]
Methionine, through S-adenosylmethionine, activates a multifaceted growth program in which ribosome biogenesis, carbon metabolism, and amino acid and nucleotide biosynthesis are induced. This growth program requires the activity of the Gcn4 transcription factor (called ATF4 in mammals), which facilitates the supply of metabolic precursors that are essential for anabolism. However, how Gcn4 itself is regulated in the presence of methionine is unknown. Here, we discover that Gcn4 protein levels are increased by methionine, despite conditions of high cell growth and translation (in which the roles of Gcn4 are not well-studied...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Adhish S. Walvekar, Ganesh Kadamur, Sreesa Sreedharan, Ritu Gupta, Rajalakshmi Srinivasan, Sunil Laxman Tags: Signal Transduction Source Type: research
A highly potent CD73 biparatopic antibody blocks organization of the enzyme active site through dual mechanisms [Methods and Resources]
The dimeric ectonucleotidase CD73 catalyzes the hydrolysis of AMP at the cell surface to form adenosine, a potent suppressor of the immune response. Blocking CD73 activity in the tumor microenvironment can have a beneficial effect on tumor eradication and is a promising approach for cancer therapy. Biparatopic antibodies binding different regions of CD73 may be a means to antagonize its enzymatic activity. A panel of biparatopic antibodies representing the pairwise combination of 11 parental monoclonal antibodies against CD73 was generated by Fab-arm exchange. Nine variants vastly exceeded the potency of their parental ant...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: James E. Stefano, Dana M. Lord, Yanfeng Zhou, Julie Jaworski, Joern Hopke, Tara Travaline, Ningning Zhang, Karen Wong, Amanda Lennon, Timothy He, Eva Bric–Furlong, Cornishia Cherrie, Tristan Magnay, Elisabeth Remy, William Brondyk, Huawei Qiu, Katar Tags: Protein Structure and Folding Source Type: research
[4Fe-4S] cluster trafficking mediated by Arabidopsis mitochondrial ISCA and NFU proteins [Enzymology]
Numerous iron-sulfur (Fe-S) proteins with diverse functions are present in the matrix and respiratory chain complexes of mitochondria. Although [4Fe-4S] clusters are the most common type of Fe-S cluster in mitochondria, the molecular mechanism of [4Fe-4S] cluster assembly and insertion into target proteins by the mitochondrial iron-sulfur cluster (ISC) maturation system is not well-understood. Here we report a detailed characterization of two late-acting Fe-S cluster-carrier proteins from Arabidopsis thaliana, NFU4 and NFU5. Yeast two-hybrid and bimolecular fluorescence complementation studies demonstrated interaction of b...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Tamanna Azam, Jonathan Przybyla–Toscano, Florence Vignols, Jeremy Couturier, Nicolas Rouhier, Michael K. Johnson Tags: Plant Biology Source Type: research
Nitro-fatty acids as activators of hSIRT6 deacetylase activity [Protein Structure and Folding]
Sirtuin 6, SIRT6, is critical for both glucose and lipid homeostasis and is involved in maintaining genomic stability under conditions of oxidative DNA damage such as those observed in age-related diseases. There is an intense search for modulators of SIRT6 activity, however, not many specific activators have been reported. Long acyl-chain fatty acids have been shown to increase the weak in vitro deacetylase activity of SIRT6 but this effect is modest at best. Herein we report that electrophilic nitro-fatty acids (nitro-oleic acid and nitro-conjugated linoleic acid) potently activate SIRT6. Binding of the nitro-fatty acid ...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Mara Carreno, Mariana Bresque, Matias R. Machado, Leonardo Santos, Rosario Duran, Dario A. Vitturi, Carlos Escande, Ana Denicola Tags: Enzymology Source Type: research
PTPN2 regulates the activation of KRAS and plays a critical role in proliferation and survival of KRAS-driven cancer cells [Signal Transduction]
RAS genes are the most commonly mutated in human cancers and play critical roles in tumor initiation, progression, and drug resistance. Identification of targets that block RAS signaling is pivotal to develop therapies for RAS-related cancer. As RAS translocation to the plasma membrane (PM) is essential for its effective signal transduction, we devised a high-content screening assay to search for genes regulating KRAS membrane association. We found that the tyrosine phosphatase PTPN2 regulates the plasma membrane localization of KRAS. Knockdown of PTPN2 reduced the proliferation and promoted apoptosis in KRAS-dependent can...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Zhangsen Huang, Mingzhu Liu, Donghe Li, Yun Tan, Ruihong Zhang, Zhizhou Xia, Peihong Wang, Bo Jiao, Ping Liu, Ruibao Ren Tags: Cell Biology Source Type: research
Therapeutic targeting of pancreatic cancer stem cells by dexamethasone modulation of the MKP-1-JNK axis [Cell Biology]
Postoperative recurrence from microscopic residual disease must be prevented to cure intractable cancers, including pancreatic cancer. Key to this goal is the elimination of cancer stem cells (CSCs) endowed with tumor-initiating capacity and drug resistance. However, current therapeutic strategies capable of accomplishing this are insufficient. Using in vitro models of CSCs and in vivo models of tumor initiation in which CSCs give rise to xenograft tumors, we show that dexamethasone induces expression of MKP-1, a MAPK phosphatase, via glucocorticoid receptor activation, thereby inactivating JNK, which is required for self-...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Shuhei Suzuki, Masashi Okada, Tomomi Sanomachi, Keita Togashi, Shizuka Seino, Atsushi Sato, Masahiro Yamamoto, Chifumi Kitanaka Tags: Molecular Bases of Disease Source Type: research
In crystallo screening for proline analog inhibitors of the proline cycle enzyme PYCR1 [Metabolism]
Pyrroline-5-carboxylate reductase 1 (PYCR1) catalyzes the biosynthetic half-reaction of the proline cycle by reducing Δ1-pyrroline-5-carboxylate (P5C) to proline through the oxidation of NAD(P)H. Many cancers alter their proline metabolism by up-regulating the proline cycle and proline biosynthesis, and knockdowns of PYCR1 lead to decreased cell proliferation. Thus, evidence is growing for PYCR1 as a potential cancer therapy target. Inhibitors of cancer targets are useful as chemical probes for studying cancer mechanisms and starting compounds for drug discovery; however, there is a notable lack of validated inhibitors fo...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Emily M. Christensen, Alexandra N. Bogner, Anke Vandekeere, Gabriela S. Tam, Sagar M. Patel, Donald F. Becker, Sarah-Maria Fendt, John J. Tanner Tags: Protein Structure and Folding Source Type: research
GUCY2D mutations in retinal guanylyl cyclase 1 provide biochemical reasons for dominant cone-rod dystrophy but not for stationary night blindness [Cell Biology]
Mutations in the GUCY2D gene coding for the dimeric human retinal membrane guanylyl cyclase (RetGC) isozyme RetGC1 cause various forms of blindness, ranging from rod dysfunction to rod and cone degeneration. We tested how the mutations causing recessive congenital stationary night blindness (CSNB), recessive Leber's congenital amaurosis (LCA1), and dominant cone–rod dystrophy-6 (CORD6) affected RetGC1 activity and regulation by RetGC-activating proteins (GCAPs) and retinal degeneration-3 protein (RD3). CSNB mutations R666W, R761W, and L911F, as well as LCA1 mutations R768W and G982VfsX39, disabled RetGC1 activation by hu...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Igor V. Peshenko, Elena V. Olshevskaya, Alexander M. Dizhoor Tags: Enzymology Source Type: research
Serum lipoprotein-derived fatty acids regulate hypoxia-inducible factor [Metabolism]
This study identifies fatty acids as a physiological modulator of HIF, defining a mechanism for lipoprotein regulation that functions in parallel to oxygen. (Source: Journal of Biological Chemistry)
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Wei Shao, Jiwon Hwang, Chune Liu, Debaditya Mukhopadhyay, Shan Zhao, Meng-Chieh Shen, Ebru S. Selen, Michael J. Wolfgang, Steven A. Farber, Peter J. Espenshade Tags: Lipids Source Type: research
ZBP1 promotes fungi-induced inflammasome activation and pyroptosis, apoptosis, and necroptosis (PANoptosis) [Microbiology]
Candida albicans and Aspergillus fumigatus are dangerous fungal pathogens with high morbidity and mortality, particularly in immunocompromised patients. Innate immune-mediated programmed cell death (pyroptosis, apoptosis, necroptosis) is an integral part of host defense against pathogens. Inflammasomes, which are canonically formed upstream of pyroptosis, have been characterized as key mediators of fungal sensing and drivers of proinflammatory responses. However, the specific cell death pathways and key upstream sensors activated in the context of Candida and Aspergillus infections are unknown. Here, we report that C. albi...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Balaji Banoth, Shraddha Tuladhar, Rajendra Karki, Bhesh Raj Sharma, Benoit Briard, Sannula Kesavardhana, Amanda Burton, Thirumala-Devi Kanneganti Tags: Microbiology Source Type: research
