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Articles 1 - 30 of 103

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

The Structure Of The Endogenous Esx-3 Secretion System, Nicole Poweleit, Nadine Czudnochowski, Rachel Nakagawa, Donovan Trinidad, Kenan C. Murphy, Christopher M. Sassetti, Oren S. Rosenberg Dec 2019

The Structure Of The Endogenous Esx-3 Secretion System, Nicole Poweleit, Nadine Czudnochowski, Rachel Nakagawa, Donovan Trinidad, Kenan C. Murphy, Christopher M. Sassetti, Oren S. Rosenberg

Open Access Articles

The ESX (or Type VII) secretion systems are protein export systems in mycobacteria and many Gram-positive bacteria that mediate a broad range of functions including virulence, conjugation, and metabolic regulation. These systems translocate folded dimers of WXG100-superfamily protein substrates across the cytoplasmic membrane. We report the cryo-electron microscopy structure of an ESX-3 system, purified using an epitope tag inserted with recombineering into the chromosome of the model organism Mycobacterium smegmatis. The structure reveals a stacked architecture that extends above and below the inner membrane of the bacterium. The ESX-3 protomer complex is assembled from a single copy of the EccB3 ...


The Pseudomonas Aeruginosa Accessory Genome Elements Influence Virulence Towards Caenorhabditis Elegans, Alejandro Vasquez-Rifo, Isana Veksler-Lublinsky, Zhenyu Cheng, Frederick M. Ausubel, Victor R. Ambros Dec 2019

The Pseudomonas Aeruginosa Accessory Genome Elements Influence Virulence Towards Caenorhabditis Elegans, Alejandro Vasquez-Rifo, Isana Veksler-Lublinsky, Zhenyu Cheng, Frederick M. Ausubel, Victor R. Ambros

Open Access Articles

BACKGROUND: Multicellular animals and bacteria frequently engage in predator-prey and host-pathogen interactions, such as the well-studied relationship between Pseudomonas aeruginosa and the nematode Caenorhabditis elegans. This study investigates the genomic and genetic basis of bacterial-driven variability in P. aeruginosa virulence towards C. elegans to provide evolutionary insights into host-pathogen relationships.

RESULTS: Natural isolates of P. aeruginosa that exhibit diverse genomes display a broad range of virulence towards C. elegans. Using gene association and genetic analysis, we identify accessory genome elements that correlate with virulence, including both known and novel virulence determinants. Among the novel genes, we find a viral-like mobile ...


A Thermophilic Phage Uses A Small Terminase Protein With A Fixed Helix-Turn-Helix Geometry, Janelle A. Hayes, Brendan J. Hilbert, Christl Gaubitz, Nicholas P. Stone, Brian A. Kelch Nov 2019

A Thermophilic Phage Uses A Small Terminase Protein With A Fixed Helix-Turn-Helix Geometry, Janelle A. Hayes, Brendan J. Hilbert, Christl Gaubitz, Nicholas P. Stone, Brian A. Kelch

University of Massachusetts Medical School Faculty Publications

Tailed bacteriophage use a DNA packaging motor to encapsulate their genome during viral particle assembly. The small terminase (TerS) component acts as a molecular matchmaker by recognizing the viral genome as well as the main motor component, the large terminase (TerL). How TerS binds DNA and the TerL protein remains unclear. Here, we identify the TerS protein of the thermophilic bacteriophage P74-26. TerSP76-26 oligomerizes into a nonamer that binds DNA, stimulates TerL ATPase activity, and inhibits TerL nuclease activity. Our cryo-EM structure shows that TerSP76-26 forms a ring with a wide central pore and radially arrayed helix-turn-helix (HTH ...


Natural Hiv-1 Nef Polymorphisms Impair Serinc5 Downregulation Activity, Steven W. Jin, Nirmin Alsahafi, Xiaomei T. Kuang, Shayda A. Swann, Mako Toyoda, Heinrich G. Gottlinger, Bruce D. Walker, Takamasa Ueno, Andres Finzi, Zabrina L. Brumme, Mark A. Brockman Nov 2019

Natural Hiv-1 Nef Polymorphisms Impair Serinc5 Downregulation Activity, Steven W. Jin, Nirmin Alsahafi, Xiaomei T. Kuang, Shayda A. Swann, Mako Toyoda, Heinrich G. Gottlinger, Bruce D. Walker, Takamasa Ueno, Andres Finzi, Zabrina L. Brumme, Mark A. Brockman

Open Access Articles

HIV-1 Nef enhances virion infectivity by counteracting host restriction factor SERINC5; however, the impact of natural Nef polymorphisms on this function is largely unknown. We characterize SERINC5 downregulation activity of 91 primary HIV-1 subtype B nef alleles, including isolates from 45 elite controllers and 46 chronic progressors. Controller-derived Nef clones display lower ability to downregulate SERINC5 (median 80% activity) compared with progressor-derived clones (median 96% activity) (p = 0.0005). We identify 18 Nef polymorphisms associated with differential function, including two CTL escape mutations that contribute to lower SERINC5 downregulation: K94E, driven by HLA-B( *)08, and H116N, driven by the protective ...


Mdt-28/Plin-1 Mediates Lipid Droplet-Microtubule Interaction Via Dlc-1 In Caenorhabditis Elegans, Kang Xie, Peng Zhang, Huimin Na, Yangli Liu, Hong Zhang, Pingsheng Liu Oct 2019

Mdt-28/Plin-1 Mediates Lipid Droplet-Microtubule Interaction Via Dlc-1 In Caenorhabditis Elegans, Kang Xie, Peng Zhang, Huimin Na, Yangli Liu, Hong Zhang, Pingsheng Liu

Open Access Articles

Ectopic lipid accumulation in lipid droplets (LD) has been linked to many metabolic diseases. In this study, DHS-3::GFP was used as a LD marker in C. elegans and a forward genetic screen was carried out to find novel LD regulators. There were 140 mutant alleles identified which were divided into four phenotypic categories: enlarged, aggregated, aggregated and small, and decreased. After genetic mapping, mutations in three known LD regulatory genes (maoc-1, dhs-28, daf-22) and a peroxisome-related gene (acox-3) were found to enlarge LDs, demonstrating the reliability of using DHS-3 as a living marker. In the screen, the cytoskeleton protein ...


Chitosan Biosynthesis And Virulence In The Human Fungal Pathogen Cryptococcus Gattii, Woei C. Lam, Rajendra Upadhya, Charles A. Specht, Abigail E. Ragsdale, Camaron R. Hole, Stuart M. Levitz, Jennifer K. Lodge Oct 2019

Chitosan Biosynthesis And Virulence In The Human Fungal Pathogen Cryptococcus Gattii, Woei C. Lam, Rajendra Upadhya, Charles A. Specht, Abigail E. Ragsdale, Camaron R. Hole, Stuart M. Levitz, Jennifer K. Lodge

Open Access Articles

Cryptococcus gattii R265 is a hypervirulent fungal strain responsible for the recent outbreak of cryptococcosis in Vancouver Island of British Columbia in Canada. It differs significantly from Cryptococcus neoformans in its natural environment, its preferred site in the mammalian host, and its pathogenesis. Our previous studies of C. neoformans have shown that the presence of chitosan, the deacetylated form of chitin, in the cell wall attenuates inflammatory responses in the host, while its absence induces robust immune responses, which in turn facilitate clearance of the fungus and induces a protective response. The results of the present investigation reveal that the ...


Principles For Enhancing Virus Capsid Capacity And Stability From A Thermophilic Virus Capsid Structure, Nicholas P. Stone, Gabriel Demo, Emily Agnello, Brian A. Kelch Oct 2019

Principles For Enhancing Virus Capsid Capacity And Stability From A Thermophilic Virus Capsid Structure, Nicholas P. Stone, Gabriel Demo, Emily Agnello, Brian A. Kelch

Open Access Articles

The capsids of double-stranded DNA viruses protect the viral genome from the harsh extracellular environment, while maintaining stability against the high internal pressure of packaged DNA. To elucidate how capsids maintain stability in an extreme environment, we use cryoelectron microscopy to determine the capsid structure of thermostable phage P74-26 to 2.8-A resolution. We find P74-26 capsids exhibit an overall architecture very similar to those of other tailed bacteriophages, allowing us to directly compare structures to derive the structural basis for enhanced stability. Our structure reveals lasso-like interactions that appear to function like catch bonds. This architecture allows the capsid ...


The Essential Role Of Carbon Metabolism In The Virulence Of Cryptococcus Neoformans, Mara Weigner Oct 2019

The Essential Role Of Carbon Metabolism In The Virulence Of Cryptococcus Neoformans, Mara Weigner

Senior Honors Theses

Cryptococcus neoformans infections are a major cause of meningoencephalitis in immunosuppressed patients worldwide. Inhaled as spores or desiccated yeast cells, C. neoformans can undergo metabolic changes in response to the new host environment that allow it to cross the blood brain barrier and cause deadly central nervous system (CNS) infections. Nutrient acquisition, and specifically carbon metabolism, is critical for survival and proliferation within the host. Notably, efficient carbon metabolism is necessary to produce the polysaccharide capsule, which is arguably C. neoformans’ most important and well-studied virulence factor. As such, a better understanding of carbon acquisition and regulation is essential for ...


Distinct Transcriptional Roles For Histone H3-K56 Acetylation During The Cell Cycle In Yeast, Salih Topal, Pauline Vasseur, Marta Radman-Livaja, Craig L. Peterson Sep 2019

Distinct Transcriptional Roles For Histone H3-K56 Acetylation During The Cell Cycle In Yeast, Salih Topal, Pauline Vasseur, Marta Radman-Livaja, Craig L. Peterson

Open Access Articles

Dynamic disruption and reassembly of promoter-proximal nucleosomes is a conserved hallmark of transcriptionally active chromatin. Histone H3-K56 acetylation (H3K56Ac) enhances these turnover events and promotes nucleosome assembly during S phase. Here we sequence nascent transcripts to investigate the impact of H3K56Ac on transcription throughout the yeast cell cycle. We find that H3K56Ac is a genome-wide activator of transcription. While H3K56Ac has a major impact on transcription initiation, it also appears to promote elongation and/or termination. In contrast, H3K56Ac represses promiscuous transcription that occurs immediately following replication fork passage, in this case by promoting efficient nucleosome assembly. We also detect ...


Extensive Ribosome And Rf2 Rearrangements During Translation Termination, Egor Svidritskiy, Gabriel Demo, Anna B. Loveland, Chen Xu, Andrei A. Korostelev Sep 2019

Extensive Ribosome And Rf2 Rearrangements During Translation Termination, Egor Svidritskiy, Gabriel Demo, Anna B. Loveland, Chen Xu, Andrei A. Korostelev

Open Access Articles

Protein synthesis ends when a ribosome reaches an mRNA stop codon. Release factors (RFs) decode the stop codon, hydrolyze peptidyl-tRNA to release the nascent protein, and then dissociate to allow ribosome recycling. To visualize termination by RF2, we resolved a cryo-EM ensemble of E. coli 70S*RF2 structures at up to 3.3 A in a single sample. Five structures suggest a highly dynamic termination pathway. Upon peptidyl-tRNA hydrolysis, the CCA end of deacyl-tRNA departs from the peptidyl transferase center. The catalytic GGQ loop of RF2 is rearranged into a long beta-hairpin that plugs the peptide tunnel, biasing a nascent ...


Molecular And Structural Mechanism Of Pan-Genotypic Hcv Ns3/4a Protease Inhibition By Glecaprevir, Jennifer Timm, Klajdi Kosovrasti, Mina Henes, Florian Leidner, Shurong Hou, Akbar Ali, Nese Kurt Yilmaz, Celia A. Schiffer Jul 2019

Molecular And Structural Mechanism Of Pan-Genotypic Hcv Ns3/4a Protease Inhibition By Glecaprevir, Jennifer Timm, Klajdi Kosovrasti, Mina Henes, Florian Leidner, Shurong Hou, Akbar Ali, Nese Kurt Yilmaz, Celia A. Schiffer

University of Massachusetts Medical School Faculty Publications

Hepatitis C virus (HCV), causative agent of chronic viral hepatitis, infects 71 million people worldwide and is divided into seven genotypes and multiple subtypes with sequence identities between 68 to 82%. While older generation direct-acting antivirals (DAAs) had varying effectiveness against different genotypes, the newest NS3/4A protease inhibitors including glecaprevir (GLE) have pan-genotypic activity. The structural basis for pan-genotypic inhibition and effects of polymorphisms on inhibitor potency were not well known due to lack of crystal structures of GLE-bound NS3/4A or genotypes other than 1. In this study, we determined the crystal structures of NS3/4A from genotypes ...


High-Resolution Cryo-Em Structures Of Outbreak Strain Human Norovirus Shells Reveal Size Variations, James Jung, Timothy Grant, Dennis R. Thomas, Chris W. Diehnelt, Nikolaus Grigorieff, Leemor Joshua-Tor Jun 2019

High-Resolution Cryo-Em Structures Of Outbreak Strain Human Norovirus Shells Reveal Size Variations, James Jung, Timothy Grant, Dennis R. Thomas, Chris W. Diehnelt, Nikolaus Grigorieff, Leemor Joshua-Tor

Open Access Articles

Noroviruses are a leading cause of foodborne illnesses worldwide. Although GII.4 strains have been responsible for most norovirus outbreaks, the assembled virus shell structures have been available in detail for only a single strain (GI.1). We present high-resolution (2.6- to 4.1-A) cryoelectron microscopy (cryo-EM) structures of GII.4, GII.2, GI.7, and GI.1 human norovirus outbreak strain virus-like particles (VLPs). Although norovirus VLPs have been thought to exist in a single-sized assembly, our structures reveal polymorphism between and within genogroups, with small, medium, and large particle sizes observed. Using asymmetric reconstruction, we were able ...


In Situ Structure Of Rotavirus Vp1 Rna-Dependent Rna Polymerase, Simon Jenni, Eric N. Salgado, Tobias Herrmann, Zongli Li, Timothy Grant, Nikolaus Grigorieff, Stefano Trapani, Leandro F. Estrozi, Stephen C. Harrison Jun 2019

In Situ Structure Of Rotavirus Vp1 Rna-Dependent Rna Polymerase, Simon Jenni, Eric N. Salgado, Tobias Herrmann, Zongli Li, Timothy Grant, Nikolaus Grigorieff, Stefano Trapani, Leandro F. Estrozi, Stephen C. Harrison

Open Access Articles

Rotaviruses, like other non-enveloped, double-strand RNA viruses, package an RNA-dependent RNA polymerase (RdRp) with each duplex of their segmented genomes. Rotavirus cell entry results in loss of an outer protein layer and delivery into the cytosol of an intact, inner capsid particle (the "double-layer particle," or DLP). The RdRp, designated VP1, is active inside the DLP; each VP1 achieves many rounds of mRNA transcription from its associated genome segment. Previous work has shown that one VP1 molecule lies close to each 5-fold axis of the icosahedrally symmetric DLP, just beneath the inner surface of its protein shell, embedded in tightly ...


Ste5 Membrane Localization Allows Mapk Pathway Signaling In Trans Between Kinases On Separate Scaffold Molecules, Rachel E. Lamson, Matthew J. Winters, Peter M. Pryciak Jun 2019

Ste5 Membrane Localization Allows Mapk Pathway Signaling In Trans Between Kinases On Separate Scaffold Molecules, Rachel E. Lamson, Matthew J. Winters, Peter M. Pryciak

University of Massachusetts Medical School Faculty Publications

The MAP kinase cascade is a ubiquitous eukaryotic signaling module that can be controlled by a diverse group of scaffold proteins. In budding yeast, activation of the mating MAP kinase cascade involves regulated membrane recruitment of the archetypal scaffold protein Ste5. This event promotes activation of the first kinase, but it also enhances subsequent signal propagation through the remainder of the cascade. By studying this latter effect, we find that membrane recruitment promotes signaling in trans between kinases on separate Ste5 molecules. First, trans signaling requires all Ste5 domains that mediate membrane recruitment, including both protein-binding and membrane-binding domains. Second ...


The Molecular Basis Of Human Igg-Mediated Enhancement Of C4b-Binding Protein Recruitment To Group A Streptococcus, David Ermert, Maisem Laabei, Antonin Weckel, Matthias Morgelin, Martin Lundqvist, Lars Bjorck, Sanjay Ram, Sara Linse, Anna M. Blom Jun 2019

The Molecular Basis Of Human Igg-Mediated Enhancement Of C4b-Binding Protein Recruitment To Group A Streptococcus, David Ermert, Maisem Laabei, Antonin Weckel, Matthias Morgelin, Martin Lundqvist, Lars Bjorck, Sanjay Ram, Sara Linse, Anna M. Blom

Open Access Articles

Streptococcus pyogenes infects over 700 million people worldwide annually. Immune evasion strategies employed by the bacteria include binding of the complement inhibitors, C4b-binding protein (C4BP) and Factor H in a human-specific manner. We recently showed that human IgG increased C4BP binding to the bacterial surface, which promoted streptococcal immune evasion and increased mortality in mice. We sought to identify how IgG promotes C4BP binding to Protein H, a member of the M protein family. Dimerization of Protein H is pivotal for enhanced binding to human C4BP. First, we illustrated that Protein H, IgG, and C4BP formed a tripartite complex. Second ...


Pesticides And Parkinson's: An Investigation Of The Effect Of Roundup Exposure On Drosophila Melanogaster, Siobhan O'Neill Apr 2019

Pesticides And Parkinson's: An Investigation Of The Effect Of Roundup Exposure On Drosophila Melanogaster, Siobhan O'Neill

Carroll College Student Undergraduate Research Festival

From commercial farms to private households, Roundup is the most commonly used herbicide in the United States. In recent years, exposure to Roundup has been correlated with a variety of health problems including Celiac Disease, birth defects, kidney and liver diseases, Alzheimer's Disease, and Parkinson's Disease. To date, the use of Roundup has been banned or restricted in several foreign countries, including the Netherlands, Portugal, Germany and Italy, because it has been classified as a possible carcinogen by the World Health Organization. The goal of this research was to determine the effects of Roundup exposure on dopaminergic neurons ...


The Nua4 Acetyltransferase And Histone H4 Acetylation Promote Replication Recovery After Topoisomerase I-Poisoning, Chiaki Noguchi, Tanu Singh, Melissa A. Ziegler, Jasmine D. Peake, Lyne Khair, Ana Aza, Toru M. Nakamura, Eishi Noguchi Apr 2019

The Nua4 Acetyltransferase And Histone H4 Acetylation Promote Replication Recovery After Topoisomerase I-Poisoning, Chiaki Noguchi, Tanu Singh, Melissa A. Ziegler, Jasmine D. Peake, Lyne Khair, Ana Aza, Toru M. Nakamura, Eishi Noguchi

Open Access Articles

BACKGROUND: Histone acetylation plays an important role in DNA replication and repair because replicating chromatin is subject to dynamic changes in its structures. However, its precise mechanism remains elusive. In this report, we describe roles of the NuA4 acetyltransferase and histone H4 acetylation in replication fork protection in the fission yeast Schizosaccharomyces pombe.

RESULTS: Downregulation of NuA4 subunits renders cells highly sensitive to camptothecin, a compound that induces replication fork breakage. Defects in NuA4 function or mutations in histone H4 acetylation sites lead to impaired recovery of collapsed replication forks and elevated levels of Rad52 DNA repair foci, indicating the ...


Characterizing Aft1/2-Grx3/4 Interaction And The Role Of Bol2 During Iron Regulation In Saccharomyces Cerevisiae, William Rivers Apr 2019

Characterizing Aft1/2-Grx3/4 Interaction And The Role Of Bol2 During Iron Regulation In Saccharomyces Cerevisiae, William Rivers

Senior Theses

Iron dysregulation has been linked to a variety of human diseases, such as anemia, Friedreich’s ataxia, X-linked sideroblastic anemia, sideroblastic-like microcytic anemia, and myopathy. Thus, it is vitally important to understand the mechanisms for regulating intracellular iron. Here, we use fluorescence microscopy techniques in live cells to study interactions of the yeast proteins Grx3/4, Aft1/2, and Bol2, which have been shown to be involved in turning off iron import when the cell has adequate iron. Modified versions of genes encoding these proteins have been incorporated into several yeast backgrounds to use fluorescence to monitor interactions under varying ...


Anti-Drug Antibody Responses Impair Prophylaxis Mediated By Aav-Delivered Hiv-1 Broadly Neutralizing Antibodies, Matthew R. Gardner, Ina Fetzer, Lisa M. Kattenhorn, Meredith E. Davis-Gardner, Amber S. Zhou, Barnett Alfant, Jesse A. Weber, Hema R. Kondur, Jose M. Martinez-Navio, Sebastian P. Fuchs, Ronald C. Desrosiers, Guangping Gao, Jeffrey D. Lifson, Michael Farzan Mar 2019

Anti-Drug Antibody Responses Impair Prophylaxis Mediated By Aav-Delivered Hiv-1 Broadly Neutralizing Antibodies, Matthew R. Gardner, Ina Fetzer, Lisa M. Kattenhorn, Meredith E. Davis-Gardner, Amber S. Zhou, Barnett Alfant, Jesse A. Weber, Hema R. Kondur, Jose M. Martinez-Navio, Sebastian P. Fuchs, Ronald C. Desrosiers, Guangping Gao, Jeffrey D. Lifson, Michael Farzan

Open Access Articles

Adeno-associated virus (AAV) delivery of potent and broadly neutralizing antibodies (bNAbs is a promising approach for the prevention of HIV-1 infection. The immunoglobulin G (IgG)1 subtype is usually selected for this application, because it efficiently mediates antibody effector functions and has a somewhat longer half-life. However, the use of IgG1-Fc has been associated with the generation of anti-drug antibodies (ADAs) that correlate with loss of antibody expression. In contrast, we have shown that expression of the antibody-like molecule eCD4-Ig bearing a rhesus IgG2-Fc domain showed reduced immunogenicity and completely protected rhesus macaques from simian-HIV (SHIV)-AD8 challenges. To directly ...


Senp3-Mediated Host Defense Response Contains Hbv Replication And Restores Protein Synthesis, Rui Xi, Botao Liu, Yan Han, Xiling Shen Jan 2019

Senp3-Mediated Host Defense Response Contains Hbv Replication And Restores Protein Synthesis, Rui Xi, Botao Liu, Yan Han, Xiling Shen

Open Access Articles

Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein ...


Principles For Enhancing Virus Capsid Capacity And Stability From A Thermophilic Virus Capsid Structure, Nicholas P. Stone, Gabriel Demo, Emily Agnello, Brian A. Kelch Jan 2019

Principles For Enhancing Virus Capsid Capacity And Stability From A Thermophilic Virus Capsid Structure, Nicholas P. Stone, Gabriel Demo, Emily Agnello, Brian A. Kelch

University of Massachusetts Medical School Faculty Publications

The capsids of double-stranded DNA viruses protect the viral genome from the harsh extracellular environment, while maintaining stability against the high internal pressure of packaged DNA. To elucidate how capsids maintain stability in an extreme environment, we used cryoelectron microscopy to determine the capsid structure of the thermostable phage P74-26. We find the P74-26 capsid exhibits an overall architecture that is very similar to those of other tailed bacteriophages, allowing us to directly compare structures to derive the structural basis for enhanced stability. Our structure reveals lasso-like interactions that appear to function like catch bonds. This architecture allows the capsid ...


Resistance From Afar: Distal Mutation V36m Allosterically Modulates The Active Site To Accentuate Drug Resistance In Hcv Ns3/4a Protease, Aysegul Ozen, Kuan-Hung Lin, Keith P. Romano, Davide Tavella, Alicia Newton, Christos J. Petropoulos, Wei Huang, Cihan Aydin, Celia A. Schiffer Dec 2018

Resistance From Afar: Distal Mutation V36m Allosterically Modulates The Active Site To Accentuate Drug Resistance In Hcv Ns3/4a Protease, Aysegul Ozen, Kuan-Hung Lin, Keith P. Romano, Davide Tavella, Alicia Newton, Christos J. Petropoulos, Wei Huang, Cihan Aydin, Celia A. Schiffer

University of Massachusetts Medical School Faculty Publications

Hepatitis C virus rapidly evolves, conferring resistance to direct acting antivirals. While resistance via active site mutations in the viral NS3/4A protease has been well characterized, the mechanism for resistance of non-active site mutations is unclear. R155K and V36M often co-evolve and while R155K alters the electrostatic network at the binding site, V36M is more than 13 Angstrom away. In this study the mechanism by which V36M confers resistance, in the context of R155K, is elucidated with drug susceptibility assays, crystal structures, and molecular dynamics (MD) simulations for three protease inhibitors: telaprevir, boceprevir and danoprevir. The R155K and R155K ...


Orbit: A New Paradigm For Genetic Engineering Of Mycobacterial Chromosomes, Kenan C. Murphy, Samantha J. Nelson, Subhalaxmi Nambi, Kadamba Papavinasasundaram, Christina E. Baer, Christopher M. Sassetti Dec 2018

Orbit: A New Paradigm For Genetic Engineering Of Mycobacterial Chromosomes, Kenan C. Murphy, Samantha J. Nelson, Subhalaxmi Nambi, Kadamba Papavinasasundaram, Christina E. Baer, Christopher M. Sassetti

Open Access Articles

Two efficient recombination systems were combined to produce a versatile method for chromosomal engineering that obviates the need to prepare double-stranded DNA (dsDNA) recombination substrates. A synthetic "targeting oligonucleotide" is incorporated into the chromosome via homologous recombination mediated by the phage Che9c RecT annealase. This oligonucleotide contains a site-specific recombination site for the directional Bxb1 integrase (Int), which allows the simultaneous integration of a "payload plasmid" that contains a cognate recombination site and a selectable marker. The targeting oligonucleotide and payload plasmid are cotransformed into a RecT- and Int-expressing strain, and drug-resistant homologous recombinants are selected in a single step ...


General Decapping Activators Target Different Subsets Of Inefficiently Translated Mrnas, Feng He, Alper Celik, Chan Wu, Allan Jacobson Dec 2018

General Decapping Activators Target Different Subsets Of Inefficiently Translated Mrnas, Feng He, Alper Celik, Chan Wu, Allan Jacobson

Open Access Articles

The Dcp1-Dcp2 decapping enzyme and the decapping activators Pat1, Dhh1, and Lsm1 regulate mRNA decapping, but their mechanistic integration is unknown. We analyzed the gene expression consequences of deleting PAT1, LSM1, or DHH1, or the DCP2 C-terminal domain, and found that: i) the Dcp2 C-terminal domain is an effector of both negative and positive regulation; ii) rather than being global activators of decapping, Pat1, Lsm1, and Dhh1 directly target specific subsets of yeast mRNAs and loss of the functions of each of these factors has substantial indirect consequences for genome-wide mRNA expression; and iii) transcripts targeted by Pat1, Lsm1, and ...


Potent Cas9 Inhibition In Bacterial And Human Cells By Acriic4 And Acriic5 Anti-Crispr Proteins, Jooyoung Lee, Aamir Mir, Alireza Edraki, Bianca Garcia, Nadia Amrani, Hannah E. Lou, Ildar Gainetdinov, April Pawluk, Raed Ibraheim, Xin D. Gao, Pengpeng Liu, Alan R. Davidson, Karen L. Maxwell, Erik J. Sontheimer Dec 2018

Potent Cas9 Inhibition In Bacterial And Human Cells By Acriic4 And Acriic5 Anti-Crispr Proteins, Jooyoung Lee, Aamir Mir, Alireza Edraki, Bianca Garcia, Nadia Amrani, Hannah E. Lou, Ildar Gainetdinov, April Pawluk, Raed Ibraheim, Xin D. Gao, Pengpeng Liu, Alan R. Davidson, Karen L. Maxwell, Erik J. Sontheimer

Open Access Articles

In their natural settings, CRISPR-Cas systems play crucial roles in bacterial and archaeal adaptive immunity to protect against phages and other mobile genetic elements, and they are also widely used as genome engineering technologies. Previously we discovered bacteriophage-encoded Cas9-specific anti-CRISPR (Acr) proteins that serve as countermeasures against host bacterial immunity by inactivating their CRISPR-Cas systems (A. Pawluk, N. Amrani, Y. Zhang, B. Garcia, et al., Cell 167:1829-1838.e9, 2016, https://doi.org/10.1016/j.cell.2016.11.017). We hypothesized that the evolutionary advantages conferred by anti-CRISPRs would drive the widespread occurrence of these proteins in nature (K ...


Deciphering The Molecular Basis Of Mycobacteria And Lipoglycan Recognition By The C-Type Lectin Dectin-2, Alexiane Decout, Devinder Kaur, Jerome Nigou Nov 2018

Deciphering The Molecular Basis Of Mycobacteria And Lipoglycan Recognition By The C-Type Lectin Dectin-2, Alexiane Decout, Devinder Kaur, Jerome Nigou

Open Access Articles

Dectin-2 is a C-type lectin involved in the recognition of several pathogens such as Aspergillus fumigatus, Candida albicans, Schistosoma mansonii, and Mycobacterium tuberculosis that triggers Th17 immune responses. Identifying pathogen ligands and understanding the molecular basis of their recognition is one of the current challenges. Purified M. tuberculosis mannose-capped lipoarabinomannan (ManLAM) was shown to induce signaling via Dectin-2, an activity that requires the (alpha1 --> 2)-linked mannosides forming the caps. Here, using isogenic M. tuberculosis mutant strains, we demonstrate that ManLAM is a bona fide and actually the sole ligand mediating bacilli recognition by Dectin-2, although M. tuberculosis produces a ...


Mutations In Influenza A Virus Neuraminidase And Hemagglutinin Confer Resistance Against A Broadly Neutralizing Hemagglutinin Stem Antibody, Kristina L. Prachanronarong, Aneth S. Canale, Ping Liu, Mohan Somasundaran, Shurong Hou, Yu-Ping Poh, Thomas Han, Quan Zhu, Nicholas Renzette, Konstantin B. Zeldovich, Timothy F. Kowalik, Nese Kurt Yilmaz, Jeffrey D. Jensen, Daniel N. Bolon, Wayne A. Marasco, Robert W. Finberg, Celia A. Schiffer, Jennifer P. Wang Oct 2018

Mutations In Influenza A Virus Neuraminidase And Hemagglutinin Confer Resistance Against A Broadly Neutralizing Hemagglutinin Stem Antibody, Kristina L. Prachanronarong, Aneth S. Canale, Ping Liu, Mohan Somasundaran, Shurong Hou, Yu-Ping Poh, Thomas Han, Quan Zhu, Nicholas Renzette, Konstantin B. Zeldovich, Timothy F. Kowalik, Nese Kurt Yilmaz, Jeffrey D. Jensen, Daniel N. Bolon, Wayne A. Marasco, Robert W. Finberg, Celia A. Schiffer, Jennifer P. Wang

Schiffer Lab Publications

Influenza A virus (IAV), a major cause of human morbidity and mortality, continuously evolves in response to selective pressures. Stem-directed, broadly neutralizing antibodies (sBnAbs) targeting influenza hemagglutinin (HA) are a promising therapeutic strategy, but neutralization escape mutants can develop. We used an integrated approach combining viral passaging, deep sequencing, and protein structural analyses to define escape mutations and mechanisms of neutralization escape in vitro for the F10 sBnAb. IAV was propagated with escalating concentrations of F10 over serial passages in cultured cells to select for escape mutations. Viral sequence analysis revealed three mutations in HA and one in neuraminidase (NA ...


Adapting Cell-Free Protein Synthesis As A Platform Technology For Education, Grace W. Chu, Max Z. Levine, Nicole E. Gregorio, Javin P. Oza Oct 2018

Adapting Cell-Free Protein Synthesis As A Platform Technology For Education, Grace W. Chu, Max Z. Levine, Nicole E. Gregorio, Javin P. Oza

STAR (STEM Teacher and Researcher) Presentations

Cell-free protein synthesis (CFPS) has emerged as an enabling biotechnology for research and biomanufacturing as it allows for the production of protein without the need for a living cell. Applications of CFPS include the construction of libraries for functional genomics and structural biology, the production of personalized medicine, and the expression of virus-like particles. The absence of a cell wall provides an open platform for direct manipulation of the reaction conditions and biological machinery. This project focuses on adapting the CFPS biotechnology to the classroom, making a hands-on bioengineering approach to learning protein synthesis accessible to students grades K-16 through ...


All-In-One Adeno-Associated Virus Delivery And Genome Editing By Neisseria Meningitidis Cas9 In Vivo, Raed Ibraheim, Chun-Qing Song, Aamir Mir, Nadia Amrani, Wen Xue, Erik J. Sontheimer Sep 2018

All-In-One Adeno-Associated Virus Delivery And Genome Editing By Neisseria Meningitidis Cas9 In Vivo, Raed Ibraheim, Chun-Qing Song, Aamir Mir, Nadia Amrani, Wen Xue, Erik J. Sontheimer

RNA Therapeutics Institute Publications

BACKGROUND: Clustered, regularly interspaced, short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) have recently opened a new avenue for gene therapy. Cas9 nuclease guided by a single-guide RNA (sgRNA) has been extensively used for genome editing. Currently, three Cas9 orthologs have been adapted for in vivo genome engineering applications: Streptococcus pyogenes Cas9 (SpyCas9), Staphylococcus aureus Cas9 (SauCas9), and Campylobacter jejuni (CjeCas9). However, additional in vivo editing platforms are needed, in part to enable a greater range of sequences to be accessed via viral vectors, especially those in which Cas9 and sgRNA are combined into a single vector genome.

RESULTS: Here ...


An Asymmetric Centromeric Nucleosome, Yuichi Ichikawa, Noriko Saitoh, Paul D. Kaufman Aug 2018

An Asymmetric Centromeric Nucleosome, Yuichi Ichikawa, Noriko Saitoh, Paul D. Kaufman

Open Access Articles

Nucleosomes contain two copies of each core histone, held together by a naturally symmetric, homodimeric histone H3-H3 interface. This symmetry has complicated efforts to determine the regulatory potential of this architecture. Through molecular design and in vivo selection, we recently generated obligately heterodimeric H3s, providing a powerful tool for discovery of the degree to which nucleosome symmetry regulates chromosomal functions in living cells (Ichikawa et al., 2017). We now have extended this tool to the centromeric H3 isoform (Cse4/CENP-A) in budding yeast. These studies indicate that a single Cse4 N- or C-terminal extension per pair of Cse4 molecules is ...