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1.
Cell ; 173(3): 762-775.e16, 2018 04 19.
Article in English | MEDLINE | ID: mdl-29677517

ABSTRACT

Mechanotransduction plays a crucial role in vascular biology. One example of this is the local regulation of vascular resistance via flow-mediated dilation (FMD). Impairment of this process is a hallmark of endothelial dysfunction and a precursor to a wide array of vascular diseases, such as hypertension and atherosclerosis. Yet the molecules responsible for sensing flow (shear stress) within endothelial cells remain largely unknown. We designed a 384-well screening system that applies shear stress on cultured cells. We identified a mechanosensitive cell line that exhibits shear stress-activated calcium transients, screened a focused RNAi library, and identified GPR68 as necessary and sufficient for shear stress responses. GPR68 is expressed in endothelial cells of small-diameter (resistance) arteries. Importantly, Gpr68-deficient mice display markedly impaired acute FMD and chronic flow-mediated outward remodeling in mesenteric arterioles. Therefore, GPR68 is an essential flow sensor in arteriolar endothelium and is a critical signaling component in cardiovascular pathophysiology.


Subject(s)
Mechanotransduction, Cellular , RNA Interference , Receptors, G-Protein-Coupled/physiology , Animals , Biocompatible Materials , Calcium/metabolism , Cell Line, Tumor , Endothelial Cells/physiology , Endothelium, Vascular/cytology , HEK293 Cells , Human Umbilical Vein Endothelial Cells , Humans , Hydrogen-Ion Concentration , Mesenteric Arteries/physiology , Mice , Mice, Inbred C57BL , Mice, Knockout , Nitric Oxide/metabolism , RNA, Small Interfering/metabolism , Receptors, G-Protein-Coupled/genetics , Shear Strength , Stress, Mechanical , Vascular Resistance
2.
Nucleic Acids Res ; 52(9): 5067-5087, 2024 May 22.
Article in English | MEDLINE | ID: mdl-38416570

ABSTRACT

CSB (Cockayne syndrome group B) and SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) are DNA translocases that belong to the SNF2 helicase family. They both are enriched at stalled replication forks. While SMARCAL1 is recruited by RPA32 to stalled forks, little is known about whether RPA32 also regulates CSB's association with stalled forks. Here, we report that CSB directly interacts with RPA, at least in part via a RPA32C-interacting motif within the N-terminal region of CSB. Modeling of the CSB-RPA32C interaction suggests that CSB binds the RPA32C surface previously shown to be important for binding of UNG2 and SMARCAL1. We show that this interaction is necessary for promoting fork slowing and fork degradation in BRCA2-deficient cells but dispensable for mediating restart of stalled forks. CSB competes with SMARCAL1 for RPA32 at stalled forks and acts non-redundantly with SMARCAL1 to restrain fork progression in response to mild replication stress. In contrast to CSB stimulated restart of stalled forks, SMARCAL1 inhibits restart of stalled forks in BRCA2-deficient cells, likely by suppressing BIR-mediated repair of collapsed forks. Loss of CSB leads to re-sensitization of SMARCAL1-depleted BRCA2-deficient cells to chemodrugs, underscoring a role of CSB in targeted cancer therapy.


Subject(s)
BRCA2 Protein , DNA Helicases , DNA Repair Enzymes , DNA Replication , Poly-ADP-Ribose Binding Proteins , Replication Protein A , DNA Helicases/metabolism , DNA Helicases/genetics , Humans , Poly-ADP-Ribose Binding Proteins/metabolism , Poly-ADP-Ribose Binding Proteins/genetics , BRCA2 Protein/metabolism , BRCA2 Protein/genetics , DNA Repair Enzymes/metabolism , DNA Repair Enzymes/genetics , Replication Protein A/metabolism , Replication Protein A/genetics , Protein Binding , Cell Line, Tumor , DNA Repair
3.
Mol Cell ; 62(1): 121-36, 2016 Apr 07.
Article in English | MEDLINE | ID: mdl-26949039

ABSTRACT

HECT-family E3 ligases ubiquitinate protein substrates to control virtually every eukaryotic process and are misregulated in numerous diseases. Nonetheless, understanding of HECT E3s is limited by a paucity of selective and potent modulators. To overcome this challenge, we systematically developed ubiquitin variants (UbVs) that inhibit or activate HECT E3s. Structural analysis of 6 HECT-UbV complexes revealed UbV inhibitors hijacking the E2-binding site and activators occupying a ubiquitin-binding exosite. Furthermore, UbVs unearthed distinct regulation mechanisms among NEDD4 subfamily HECTs and proved useful for modulating therapeutically relevant targets of HECT E3s in cells and intestinal organoids, and in a genetic screen that identified a role for NEDD4L in regulating cell migration. Our work demonstrates versatility of UbVs for modulating activity across an E3 family, defines mechanisms and provides a toolkit for probing functions of HECT E3s, and establishes a general strategy for systematic development of modulators targeting families of signaling proteins.


Subject(s)
Ubiquitin-Protein Ligases/chemistry , Ubiquitin-Protein Ligases/metabolism , Ubiquitin/metabolism , Animals , Catalytic Domain , Cell Line , Cell Movement , Dogs , HCT116 Cells , Humans , Madin Darby Canine Kidney Cells , Models, Molecular , Organoids/cytology , Organoids/metabolism , Peptide Library , Ubiquitin/chemistry , Ubiquitin/genetics
4.
Nucleic Acids Res ; 49(22): 12836-12854, 2021 12 16.
Article in English | MEDLINE | ID: mdl-34871413

ABSTRACT

Cockayne syndrome group B (CSB) protein has been implicated in the repair of a variety of DNA lesions that induce replication stress. However, little is known about its role at stalled replication forks. Here, we report that CSB is recruited to stalled forks in a manner dependent upon its T1031 phosphorylation by CDK. While dispensable for MRE11 association with stalled forks in wild-type cells, CSB is required for further accumulation of MRE11 at stalled forks in BRCA1/2-deficient cells. CSB promotes MRE11-mediated fork degradation in BRCA1/2-deficient cells. CSB possesses an intrinsic ATP-dependent fork reversal activity in vitro, which is activated upon removal of its N-terminal region that is known to autoinhibit CSB's ATPase domain. CSB functions similarly to fork reversal factors SMARCAL1, ZRANB3 and HLTF to regulate slowdown in fork progression upon exposure to replication stress, indicative of a role of CSB in fork reversal in vivo. Furthermore, CSB not only acts epistatically with MRE11 to facilitate fork restart but also promotes RAD52-mediated break-induced replication repair of double-strand breaks arising from cleavage of stalled forks by MUS81 in BRCA1/2-deficient cells. Loss of CSB exacerbates chemosensitivity in BRCA1/2-deficient cells, underscoring an important role of CSB in the treatment of cancer lacking functional BRCA1/2.


Subject(s)
BRCA1 Protein/genetics , BRCA2 Protein/genetics , DNA Helicases/genetics , DNA Repair Enzymes/genetics , DNA Repair , DNA/genetics , MRE11 Homologue Protein/genetics , Poly-ADP-Ribose Binding Proteins/genetics , BRCA1 Protein/deficiency , BRCA1 Protein/metabolism , BRCA2 Protein/deficiency , BRCA2 Protein/metabolism , Cell Line , Cell Line, Tumor , DNA/chemistry , DNA/metabolism , DNA Breaks, Double-Stranded , DNA Helicases/metabolism , DNA Repair Enzymes/metabolism , DNA Replication/genetics , HCT116 Cells , HEK293 Cells , Humans , MRE11 Homologue Protein/metabolism , Mutation , Poly-ADP-Ribose Binding Proteins/metabolism , RNA Interference
5.
Int J Mol Sci ; 24(15)2023 Aug 04.
Article in English | MEDLINE | ID: mdl-37569794

ABSTRACT

Topoisomerase inhibitor camptothecin (CPT) induces fork stalling and is highly toxic to proliferating cells. However, how cells respond to CPT-induced fork stalling has not been fully characterized. Here, we report that Cockayne syndrome group B (CSB) protein inhibits PRIMPOL-dependent fork repriming in response to a low dose of CPT. At a high concentration of CPT, CSB is required to promote the restart of DNA replication through MUS81-RAD52-POLD3-dependent break-induced replication (BIR). In the absence of CSB, resumption of DNA synthesis at a high concentration of CPT can occur through POLQ-LIG3-, LIG4-, or PRIMPOL-dependent pathways, which are inhibited, respectively, by RAD51, BRCA1, and BRCA2 proteins. POLQ and LIG3 are core components of alternative end joining (Alt-EJ), whereas LIG4 is a core component of nonhomologous end joining (NHEJ). These results suggest that CSB regulates fork restart pathway choice following high-dosage CPT-induced fork stalling, promoting BIR but inhibiting Alt-EJ, NHEJ, and fork repriming. We find that loss of CSB and BRCA2 is a toxic combination to genomic stability and cell survival at a high concentration of CPT, which is likely due to accumulation of ssDNA gaps, underscoring an important role of CSB in regulating the therapy response in cancers lacking functional BRCA2.


Subject(s)
DNA Repair , DNA Replication , DNA End-Joining Repair , Camptothecin/pharmacology
6.
J Cell Sci ; 133(4)2020 02 17.
Article in English | MEDLINE | ID: mdl-31974116

ABSTRACT

Elevated replication stress is evident at telomeres of about 10-15% of cancer cells, which maintain their telomeres via a homologous recombination (HR)-based mechanism, referred to as alternative lengthening of telomeres (ALT). How ALT cells resolve replication stress to support their growth remains incompletely characterized. Here, we report that CSB (also known as ERCC6) promotes recruitment of HR repair proteins (MRN, BRCA1, BLM and RPA32) and POLD3 to ALT telomeres, a process that requires the ATPase activity of CSB and is controlled by ATM- and CDK2-dependent phosphorylation. Loss of CSB stimulates telomeric recruitment of MUS81 and SLX4, components of the structure-specific MUS81-EME1-SLX1-SLX4 (MUS-SLX) endonuclease complex, suggesting that CSB restricts MUS-SLX-mediated processing of stalled forks at ALT telomeres. Loss of CSB coupled with depletion of SMARCAL1, a chromatin remodeler implicated in catalyzing regression of stalled forks, synergistically promotes not only telomeric recruitment of MUS81 but also the formation of fragile telomeres, the latter of which is reported to arise from fork stalling. These results altogether suggest that CSB-mediated HR repair and SMARCAL1-mediated fork regression cooperate to prevent stalled forks from being processed into fragile telomeres in ALT cells.


Subject(s)
Telomere Homeostasis , Telomere , DNA Repair , Endonucleases/metabolism , Homologous Recombination , Telomere/genetics , Telomere/metabolism , Telomere Homeostasis/genetics
7.
Nature ; 537(7619): 229-233, 2016 09 08.
Article in English | MEDLINE | ID: mdl-27501246

ABSTRACT

Chagas disease, leishmaniasis and sleeping sickness affect 20 million people worldwide and lead to more than 50,000 deaths annually. The diseases are caused by infection with the kinetoplastid parasites Trypanosoma cruzi, Leishmania spp. and Trypanosoma brucei spp., respectively. These parasites have similar biology and genomic sequence, suggesting that all three diseases could be cured with drugs that modulate the activity of a conserved parasite target. However, no such molecular targets or broad spectrum drugs have been identified to date. Here we describe a selective inhibitor of the kinetoplastid proteasome (GNF6702) with unprecedented in vivo efficacy, which cleared parasites from mice in all three models of infection. GNF6702 inhibits the kinetoplastid proteasome through a non-competitive mechanism, does not inhibit the mammalian proteasome or growth of mammalian cells, and is well-tolerated in mice. Our data provide genetic and chemical validation of the parasite proteasome as a promising therapeutic target for treatment of kinetoplastid infections, and underscore the possibility of developing a single class of drugs for these neglected diseases.


Subject(s)
Chagas Disease/drug therapy , Kinetoplastida/drug effects , Kinetoplastida/enzymology , Leishmaniasis/drug therapy , Proteasome Endopeptidase Complex/drug effects , Proteasome Inhibitors/pharmacology , Proteasome Inhibitors/therapeutic use , Pyrimidines/pharmacology , Triazoles/pharmacology , Trypanosomiasis, African/drug therapy , Animals , Chagas Disease/parasitology , Chymotrypsin/antagonists & inhibitors , Chymotrypsin/metabolism , Disease Models, Animal , Female , Humans , Inhibitory Concentration 50 , Leishmaniasis/parasitology , Mice , Molecular Structure , Molecular Targeted Therapy , Proteasome Inhibitors/adverse effects , Proteasome Inhibitors/classification , Pyrimidines/adverse effects , Pyrimidines/chemistry , Pyrimidines/therapeutic use , Species Specificity , Triazoles/adverse effects , Triazoles/chemistry , Triazoles/therapeutic use , Trypanosomiasis, African/parasitology
8.
Proc Natl Acad Sci U S A ; 116(28): 14164-14173, 2019 07 09.
Article in English | MEDLINE | ID: mdl-31239348

ABSTRACT

The cyclic guanosine-3',5'-monophosphate (cGMP)-dependent protein kinase (PKG) was identified >25 y ago; however, efforts to obtain a structure of the entire PKG enzyme or catalytic domain from any species have failed. In malaria parasites, cooperative activation of PKG triggers crucial developmental transitions throughout the complex life cycle. We have determined the cGMP-free crystallographic structures of PKG from Plasmodium falciparum and Plasmodium vivax, revealing how key structural components, including an N-terminal autoinhibitory segment (AIS), four predicted cyclic nucleotide-binding domains (CNBs), and a kinase domain (KD), are arranged when the enzyme is inactive. The four CNBs and the KD are in a pentagonal configuration, with the AIS docked in the substrate site of the KD in a swapped-domain dimeric arrangement. We show that although the protein is predominantly a monomer (the dimer is unlikely to be representative of the physiological form), the binding of the AIS is necessary to keep Plasmodium PKG inactive. A major feature is a helix serving the dual role of the N-terminal helix of the KD as well as the capping helix of the neighboring CNB. A network of connecting helices between neighboring CNBs contributes to maintaining the kinase in its inactive conformation. We propose a scheme in which cooperative binding of cGMP, beginning at the CNB closest to the KD, transmits conformational changes around the pentagonal molecule in a structural relay mechanism, enabling PKG to orchestrate rapid, highly regulated developmental switches in response to dynamic modulation of cGMP levels in the parasite.


Subject(s)
Cyclic GMP-Dependent Protein Kinases/chemistry , Malaria/genetics , Plasmodium falciparum/chemistry , Protein Conformation , Amino Acid Sequence/genetics , Animals , Binding Sites/genetics , Catalytic Domain/genetics , Crystallography, X-Ray , Cyclic GMP/chemistry , Cyclic GMP-Dependent Protein Kinases/genetics , Cyclic GMP-Dependent Protein Kinases/ultrastructure , Humans , Kinetics , Malaria/parasitology , Plasmodium falciparum/pathogenicity , Plasmodium falciparum/ultrastructure , Protein Binding
9.
Int J Mol Sci ; 23(18)2022 Sep 06.
Article in English | MEDLINE | ID: mdl-36142121

ABSTRACT

A variety of endogenous and exogenous insults are capable of impeding replication fork progression, leading to replication stress. Several SNF2 fork remodelers have been shown to play critical roles in resolving this replication stress, utilizing different pathways dependent upon the nature of the DNA lesion, location on the DNA, and the stage of the cell cycle, to complete DNA replication in a manner preserving genetic integrity. Under certain conditions, however, the attempted repair may lead to additional genetic instability. Cockayne syndrome group B (CSB) protein, a SNF2 chromatin remodeler best known for its role in transcription-coupled nucleotide excision repair, has recently been shown to catalyze fork reversal, a pathway that can provide stability of stalled forks and allow resumption of DNA synthesis without chromosome breakage. Prolonged stalling of replication forks may collapse to give rise to DNA double-strand breaks, which are preferentially repaired by homology-directed recombination. CSB plays a role in repairing collapsed forks by promoting break-induced replication in S phase and early mitosis. In this review, we discuss roles of CSB in regulating the sources of replication stress, replication stress response, as well as the implications of CSB for cancer therapy.


Subject(s)
Cockayne Syndrome , Neoplasms , Chromatin , Cockayne Syndrome/genetics , DNA/metabolism , DNA Repair , DNA Replication , DNA-Binding Proteins/metabolism , Humans , Neoplasms/genetics , Neoplasms/therapy
10.
Nat Methods ; 15(11): 941-946, 2018 11.
Article in English | MEDLINE | ID: mdl-30297964

ABSTRACT

CRISPR-Cas9 screening allows genome-wide interrogation of gene function. Currently, to achieve the high and uniform Cas9 expression desirable for screening, one needs to engineer stable and clonal Cas9-expressing cells-an approach that is not applicable in human primary cells. Guide Swap permits genome-scale pooled CRISPR-Cas9 screening in human primary cells by exploiting the unexpected finding that editing by lentivirally delivered, targeted guide RNAs (gRNAs) occurs efficiently when Cas9 is introduced in complex with nontargeting gRNA. We validated Guide Swap in depletion and enrichment screens in CD4+ T cells. Next, we implemented Guide Swap in a model of ex vivo hematopoiesis, and identified known and previously unknown regulators of CD34+ hematopoietic stem and progenitor cell (HSPC) expansion. We anticipate that this platform will be broadly applicable to other challenging cell types, and thus will enable discovery in previously inaccessible but biologically relevant human primary cell systems.


Subject(s)
CD8-Positive T-Lymphocytes/metabolism , CRISPR-Associated Protein 9/metabolism , CRISPR-Cas Systems , Gene Editing , Genome, Human , Hematopoietic Stem Cells/metabolism , RNA, Guide, Kinetoplastida/genetics , CD8-Positive T-Lymphocytes/cytology , Cells, Cultured , HEK293 Cells , Hematopoietic Stem Cells/cytology , Humans
11.
Nucleic Acids Res ; 47(20): 10678-10692, 2019 11 18.
Article in English | MEDLINE | ID: mdl-31501894

ABSTRACT

CSB, a member of the SWI2/SNF2 superfamily, has been implicated in evicting histones to promote the DSB pathway choice towards homologous recombination (HR) repair. However, how CSB promotes HR repair remains poorly characterized. Here we demonstrate that CSB interacts with both MRE11/RAD50/NBS1 (MRN) and BRCA1 in a cell cycle regulated manner, with the former requiring its WHD and occurring predominantly in early S phase. CSB interacts with the BRCT domain of BRCA1 and this interaction is regulated by CDK-dependent phosphorylation of CSB on S1276. The CSB-BRCA1 interaction, which peaks in late S/G2 phase, is responsible for mediating the interaction of CSB with the BRCA1-C complex consisting of BRCA1, MRN and CtIP. While dispensable for histone eviction at DSBs, CSB phosphorylation on S1276 is necessary to promote efficient MRN- and CtIP-mediated DNA end resection, thereby restricting NHEJ and enforcing the DSB repair pathway choice to HR. CSB phosphorylation on S1276 is also necessary to support cell survival in response to DNA damage-inducing agents. These results altogether suggest that CSB interacts with BRCA1 to promote DNA end resection for HR repair and that although prerequisite, CSB-mediated histone eviction alone is insufficient to promote the pathway choice towards HR.


Subject(s)
BRCA1 Protein/metabolism , DNA Helicases/metabolism , DNA Repair Enzymes/metabolism , DNA Repair , Endodeoxyribonucleases/metabolism , G2 Phase , Multiprotein Complexes/metabolism , Poly-ADP-Ribose Binding Proteins/metabolism , S Phase , BRCA1 Protein/chemistry , Camptothecin/pharmacology , Cell Line, Tumor , Cell Survival/drug effects , Chromatin Assembly and Disassembly/drug effects , DNA Breaks, Double-Stranded/drug effects , DNA Helicases/chemistry , DNA Repair/drug effects , DNA Repair Enzymes/chemistry , G2 Phase/drug effects , Humans , Phosphorylation/drug effects , Phosphoserine/metabolism , Phthalazines/pharmacology , Piperazines/pharmacology , Poly-ADP-Ribose Binding Proteins/chemistry , Protein Binding/drug effects , Protein Domains , S Phase/drug effects , Telomere-Binding Proteins/metabolism
12.
Int J Mol Sci ; 22(7)2021 Mar 25.
Article in English | MEDLINE | ID: mdl-33806087

ABSTRACT

Cockayne syndrome group B protein (CSB), a member of the SWI/SNF superfamily, resides in an elongating RNA polymerase II (RNAPII) complex and regulates transcription elongation. CSB contains a C-terminal winged helix domain (WHD) that binds to ubiquitin and plays an important role in DNA repair. However, little is known about the role of the CSB-WHD in transcription regulation. Here, we report that CSB is dependent upon its WHD to regulate RNAPII abundance at promoter proximal pause (PPP) sites of several actively transcribed genes, a key step in the regulation of transcription elongation. We show that two ubiquitin binding-defective mutations in the CSB-WHD, which impair CSB's ability to promote cell survival in response to treatment with cisplatin, have little impact on its ability to stimulate RNAPII occupancy at PPP sites. In addition, we demonstrate that two cancer-associated CSB mutations, which are located on the opposite side of the CSB-WHD away from its ubiquitin-binding pocket, impair CSB's ability to promote RNAPII occupancy at PPP sites. Taken together, these results suggest that CSB promotes RNAPII association with PPP sites in a manner requiring the CSB-WHD but independent of its ubiquitin-binding activity. These results further imply that CSB-mediated RNAPII occupancy at PPP sites is mechanistically separable from CSB-mediated repair of cisplatin-induced DNA damage.


Subject(s)
DNA Helicases/metabolism , DNA Repair Enzymes/metabolism , DNA Repair , Gene Expression Regulation , Mutation , Neoplasms/genetics , Poly-ADP-Ribose Binding Proteins/metabolism , RNA Polymerase II/metabolism , Cell Line, Tumor , Cell Survival , Cisplatin/adverse effects , Cisplatin/pharmacology , DNA Damage/drug effects , DNA Helicases/chemistry , DNA Repair Enzymes/chemistry , Humans , Poly-ADP-Ribose Binding Proteins/chemistry , Promoter Regions, Genetic , Protein Binding , Transcription Factors/metabolism , Ubiquitin/metabolism
13.
Neurobiol Dis ; 134: 104683, 2020 02.
Article in English | MEDLINE | ID: mdl-31765727

ABSTRACT

Repeated mild traumatic brain injury (rmTBI) can lead to development of chronic traumatic encephalopathy (CTE), which is characterized by progressive neurodegeneration with presence of white matter damage, gliosis and hyper-phosphorylated tau. While animal models of rmTBI have been documented, few characterize the molecular pathogenesis and expression profiles of relevant injured brain regions. Additionally, while the usage of transgenic tau mice in rmTBI is prevalent, the effects of tau on pathological outcomes has not been well studied. Here we characterized a 42-impact closed-head rmTBI paradigm on 3-4 month old male C57BL/6 (WT) and Tau-overexpressing mice (Tau58.4). This injury paradigm resulted in chronic gliosis, T-cell infiltration, and demyelination of the optic nerve and associated white matter tracts at 1-month post-injury. At 3-months post-injury, Tau58.4 mice showed progressive neuroinflammation and neurodegeneration in multiple brain regions compared to WT mice. Corresponding to histopathology, RNAseq of the optic nerve tract at 1-month post-injury showed significant upregulation of inflammatory pathways and downregulation of myelin synthetic pathways in both genotypes. However, Tau58.4 mice showed additional changes in neurite development, protein processing, and cell stress. Comparisons with published transcriptomes of human Alzheimer's Disease and CTE revealed common signatures including neuroinflammation and downregulation of protein phosphatases. We next investigated the demyelination and T-cell infiltration phenotypes to determine whether these offer potential avenues for therapeutic intervention. Tau58.4 mice were treated with the histamine H3 receptor antagonist GSK239512 for 1-month post-injury to promote remyelination of white matter lesions. This restored myelin gene expression to sham levels but failed to repair the histopathologic lesions. Likewise, injured T-cell-deficient Rag2/Il2rg (R2G2) mice also showed evidence for inflammation and loss of myelin. However, unlike immune-competent mice, R2G2 mice had altered myeloid cell gene expression and fewer demyelinated lesions. Together this data shows that rmTBI leads to chronic white matter inflammatory demyelination and axonal loss exacerbated by human tau overexpression but suggests that immune-suppression and remyelination alone are insufficient to reverse damage.


Subject(s)
Brain Concussion/metabolism , Brain Concussion/pathology , Brain/metabolism , Brain/pathology , tau Proteins/metabolism , Animals , Brain Concussion/complications , Encephalitis/complications , Encephalitis/metabolism , Encephalitis/pathology , Male , Mice, Inbred C57BL , Mice, Transgenic , White Matter/metabolism , White Matter/pathology
14.
Article in English | MEDLINE | ID: mdl-31658970

ABSTRACT

Upregulated expression of efflux pumps, lpxC target mutations, LpxC protein overexpression, and mutations in fabG were previously shown to mediate single-step resistance to the LpxC inhibitor CHIR-090 in P. aeruginosa Single-step selection experiments using three recently described LpxC inhibitors (compounds 2, 3, and 4) and mutant characterization showed that these mechanisms affect susceptibility to additional novel LpxC inhibitors. Serial passaging of P. aeruginosa wild-type and efflux pump-defective strains using the LpxC inhibitor CHIR-090 or compound 1 generated substantial shifts in susceptibility and underscored the interplay of efflux and nonefflux mechanisms. Whole-genome sequencing of CHIR-090 passage mutants identified efflux pump overexpression, fabG mutations, and novel mutations in fabF1 and in PA4465 as determinants of reduced susceptibility. Two new lpxC mutations, encoding A214V and G208S, that reduce susceptibility to certain LpxC inhibitors were identified in these studies, and we show that these and other target mutations differentially affect different LpxC inhibitor scaffolds. Lastly, the combination of target alteration (LpxCA214V) and upregulated expression of LpxC was shown to be tolerated in P. aeruginosa and could mediate significant decreases in susceptibility.


Subject(s)
Pseudomonas aeruginosa/drug effects , Amidohydrolases/genetics , Amidohydrolases/metabolism , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Microbial Sensitivity Tests , Mutation/genetics , Pseudomonas aeruginosa/genetics , Whole Genome Sequencing
15.
Article in English | MEDLINE | ID: mdl-31036686

ABSTRACT

Antibiotic hypersensitive bacterial mutants (e.g., Escherichia coliimp) are used to investigate intrinsic resistance and are exploited in antibacterial discovery to track weak antibacterial activity of novel inhibitor compounds. Pseudomonas aeruginosa Z61 is one such drug-hypersusceptible strain generated by chemical mutagenesis, although the genetic basis for hypersusceptibility is not fully understood. Genome sequencing of Z61 revealed nonsynonymous single-nucleotide polymorphisms in 153 genes relative to its parent strain, and three candidate mutations (in oprM, ampC, and lptE) predicted to mediate hypersusceptibility were characterized. The contribution of these mutations was confirmed by genomic restoration of the wild-type sequences, individually or in combination, in the Z61 background. Introduction of the lptE mutation or genetic inactivation of oprM and ampC genes alone or together in the parent strain recapitulated drug sensitivities. This showed that disruption of oprM (which encodes a major outer membrane efflux pump channel) increased susceptibility to pump substrate antibiotics, that inactivation of the inducible ß-lactamase gene ampC contributed to ß-lactam susceptibility, and that mutation of the lipopolysaccharide transporter gene lptE strongly altered the outer membrane permeability barrier, causing susceptibility to large antibiotics such as rifampin and also to ß-lactams.


Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Lipopolysaccharides/metabolism , Membrane Transport Proteins/genetics , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/genetics , beta-Lactamases/genetics , Bacterial Outer Membrane Proteins/genetics , Biological Transport/genetics , Cell Membrane Permeability/genetics , Microbial Sensitivity Tests/methods , Mutation/genetics , beta-Lactams/pharmacology
16.
Article in English | MEDLINE | ID: mdl-30420483

ABSTRACT

Efflux pumps contribute to antibiotic resistance in Gram-negative pathogens. Correspondingly, efflux pump inhibitors (EPIs) may reverse this resistance. D13-9001 specifically inhibits MexAB-OprM in Pseudomonas aeruginosa Mutants with decreased susceptibility to MexAB-OprM inhibition by D13-9001 were identified, and these fell into two categories: those with alterations in the target MexB (F628L and ΔV177) and those with an alteration in a putative sensor kinase of unknown function, PA1438 (L172P). The alterations in MexB were consistent with reported structural studies of the D13-9001 interaction with MexB. The PA1438L172P alteration mediated a >150-fold upregulation of MexMN pump gene expression and a >50-fold upregulation of PA1438 and the neighboring response regulator gene, PA1437. We propose that these be renamed mmnR and mmnS for MexMN regulator and MexMN sensor, respectively. MexMN was shown to partner with the outer membrane channel protein OprM and to pump several ß-lactams, monobactams, and tazobactam. Upregulated MexMN functionally replaced MexAB-OprM to efflux these compounds but was insusceptible to inhibition by D13-9001. MmnSL172P also mediated a decrease in susceptibility to imipenem and biapenem that was independent of MexMN-OprM. Expression of oprD, encoding the uptake channel for these compounds, was downregulated, suggesting that this channel is also part of the MmnSR regulon. Transcriptome sequencing (RNA-seq) of cells encoding MmnSL172P revealed, among other things, an interrelationship between the regulation of mexMN and genes involved in heavy metal resistance.


Subject(s)
Piperidines/pharmacology , Pseudomonas aeruginosa/drug effects , Quaternary Ammonium Compounds/pharmacology , beta-Lactams/pharmacology , Imipenem/pharmacology , Microbial Sensitivity Tests , Monobactams/pharmacology , Pseudomonas aeruginosa/genetics , Tazobactam/pharmacology , Thienamycins/pharmacology , Transcriptome/genetics
17.
J Cell Sci ; 129(13): 2559-72, 2016 07 01.
Article in English | MEDLINE | ID: mdl-27185864

ABSTRACT

TRF1, a duplex telomeric DNA binding protein, is implicated in homologous-recombination-based alternative lengthening of telomeres, known as ALT. However, how TRF1 promotes ALT activity has yet to be fully characterized. Here we report that Cdk-dependent TRF1 phosphorylation on T371 acts as a switch to create a pool of TRF1, referred to as (pT371)TRF1, which is recruited to ALT-associated PML bodies (APBs) in S and G2 phases independently of its binding to telomeric DNA. We find that phosphorylation of T371 is essential for APB formation and C-circle production, both of which are hallmarks of ALT. We show that the interaction of (pT371)TRF1 with APBs is dependent upon ATM and homologous-recombination-promoting factors Mre11 and BRCA1. In addition, (pT371)TRF1 interaction with APBs is sensitive to transcription inhibition, which also reduces DNA damage at telomeres. Furthermore, overexpression of RNaseH1 impairs (pT371)TRF1 recruitment to APBs in the presence of campothecin, an inhibitor that prevents topoisomerase I from resolving RNA-DNA hybrids. These results suggest that transcription-associated DNA damage, perhaps arising from processing RNA-DNA hybrids at telomeres, triggers (pT371)TRF1 recruitment to APBs to facilitate ALT activity.


Subject(s)
BRCA1 Protein/genetics , CDC2 Protein Kinase/genetics , DNA-Binding Proteins/genetics , Telomere Homeostasis/genetics , Telomeric Repeat Binding Protein 1/genetics , Cell Line , DNA Damage/genetics , Gene Expression Regulation , Homologous Recombination/genetics , Humans , Intranuclear Inclusion Bodies/genetics , MRE11 Homologue Protein , Phosphorylation , Ribonuclease H/genetics , Telomere/genetics
18.
Am J Gastroenterol ; 113(12): 1810-1818, 2018 12.
Article in English | MEDLINE | ID: mdl-30385831

ABSTRACT

OBJECTIVES: Addressing procedure-related anxiety should improve adherence to colorectal cancer screening programs and diagnostic colonoscopy. We performed a systematic review to assess anxiety among individuals undergoing colonoscopy or flexible sigmoidoscopy (FS). METHODS: We searched multiple electronic databases for studies evaluating anxiety associated with colonoscopy or FS published from 2005 to 2017. Two reviewers independently identified studies, extracted data, and assessed study quality. The main outcomes were the magnitude of pre-procedure anxiety, types of concerns, predictors of anxiety, and effectiveness of anxiety-lowering interventions in individuals undergoing lower endoscopy. The protocol was prospectively registered in PROSPERO. RESULTS: Fifty-eight studies (24,490 patients) met the inclusion criteria. Patients undergoing colonoscopy had a higher mean level of anxiety than that previously reported in the general population, with some studies reporting more than 50% of patients having moderate-to-severe anxiety. Areas of anxiety-related concern included bowel preparation, difficulties with the procedure (embarrassment, pain, possible complications, and sedation), and concerns about diagnosis; including fear of being diagnosed with cancer. Female gender, higher baseline anxiety, functional abdominal pain, lower education, and lower income were associated with greater anxiety prior to colonoscopy. Providing higher-quality information before colonoscopy, particularly with a video, shows promise as a way of reducing pre-procedure anxiety but the studies to date are of low quality. CONCLUSIONS: A large proportion of patients undergoing colonoscopy report anxiety before the procedure. Improvement in pre-procedure information delivery and evaluation of approaches to reduce anxiety is required, especially for those with predictors of pre-procedure anxiety.


Subject(s)
Anxiety/epidemiology , Colonoscopy/adverse effects , Colorectal Neoplasms/diagnostic imaging , Early Detection of Cancer/adverse effects , Sigmoidoscopy/adverse effects , Anxiety/diagnosis , Anxiety/etiology , Anxiety/psychology , Colonoscopy/methods , Colonoscopy/psychology , Early Detection of Cancer/methods , Early Detection of Cancer/psychology , Humans , Patient Education as Topic , Preoperative Period , Prevalence , Severity of Illness Index , Sigmoidoscopy/methods , Sigmoidoscopy/psychology
19.
Arch Womens Ment Health ; 21(6): 813-820, 2018 12.
Article in English | MEDLINE | ID: mdl-29931445

ABSTRACT

The Internet is an easily accessible source of information for women experiencing anxiety in pregnancy and/or postpartum to use when seeking health information. However, the Internet has several drawbacks, including inaccurate content that may be perceived as being accurate, non-biased, and evidence-based. Prior research indicates that anxiety and postpartum mental health websites have poor quality in terms of describing treatment options. There is a lack of research and knowledge in the area of perinatal anxiety, and an absence of research evaluating perinatal anxiety websites. The purpose of this study was to evaluate the quality of information regarding perinatal anxiety available on the Internet. Websites concerning perinatal anxiety were selected using the Google search engine. Each website was evaluated based on quality of health information, website usability, and readability. The 20 websites included in this study had low to moderate quality scores based on the DISCERN tool. There were no associations found between website order and website quality, or between website readability and website quality. Many websites had high PEMAT scores for the understandability section, which included content, style, and layout of information; however, most did not use visual aids to enhance comprehension. Most websites had low actionability scores, suggesting that information may not be useful in describing what actions may be taken to manage perinatal anxiety. This study highlights the need for high-quality websites concerning perinatal anxiety that are easy to navigate and provide the public with evidence-based information.


Subject(s)
Anxiety , Consumer Health Information , Internet/standards , Perinatal Care , Pregnancy Complications , Access to Information , Consumer Health Information/methods , Consumer Health Information/standards , Female , Humans , Pregnancy , Software/standards
20.
BMC Health Serv Res ; 18(1): 782, 2018 Oct 17.
Article in English | MEDLINE | ID: mdl-30333033

ABSTRACT

BACKGROUND: Colonoscopy has become a common medical procedure due to increased use of colonoscopy for evaluation of symptoms, colorectal cancer screening and surveillance of people with higher risks of developing colorectal cancer. Timely access to colonoscopy is essential for diagnosis of colorectal cancer, as well as diagnosis and management of inflammatory bowel disease and gastrointestinal symptoms such as diarrhea. The purpose of this study was to obtain the perspectives of primary care providers and endoscopists about current practices, barriers and facilitators to following recommended practice for preparation and follow-up after colonoscopy. We also aimed to obtain recommendations for approaches to improve the process. METHODS: Six focus groups (two with gastroenterologists, two with surgeons who perform colonoscopies and two with primary care providers) were held between October 2015 and January 2016. Analysis was performed using inductive qualitative approaches. RESULTS: Variations and challenges in communication for continuity of care and understanding the distribution of responsibility were identified, as were perceived benefits and challenges of a central intake system for colonoscopies. Recommendations were made to improve processes including strengthening communication and information sharing. A comprehensive quality improvement plan would facilitate implementation of recommendations. CONCLUSIONS: Findings emphasize the need for improved patient-focused information resources for each step of the colonoscopy process and improved communication among practitioners. The findings apply to other services requiring collaboration among patients, primary care providers, and medical specialists.


Subject(s)
Colonic Neoplasms/diagnosis , Colonoscopy , Inflammatory Bowel Diseases/diagnosis , Primary Health Care , Colonic Neoplasms/pathology , Continuity of Patient Care , Early Detection of Cancer , Female , Focus Groups , Follow-Up Studies , Health Personnel , Humans , Inflammatory Bowel Diseases/pathology , Male , Middle Aged , Qualitative Research , Quality Improvement
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