Localization matters: nuclear-trapped Survivin sensitizes glioblastoma cells to temozolomide by elevating cellular senescence and impairing homologous recombination

AbstractTo clarify whether differential compartmentalization of Survivin impacts temozolomide (TMZ)-triggered end points, we established a well-defined glioblastoma cell model in vitro (LN229 and A172) and in vivo, distinguishing between its nuclear and cytoplasmic localization. Expression of nuclear export sequence (NES)-mutated Survivin (SurvNESmut-GFP) led to impaired colony formation upon TMZ. This was not due to enhanced cell death but rather due to increased senescence. Nuclear-trapped Survivin reduced homologous recombination (HR)-mediated double-strand break (DSB) repair, as evaluated by γH2AX foci formation and qPCR-based HR assay leading to pronounced induction of chromosome aberrations. Opposite, clones, expressing free-shuttling cytoplasmic but not nuclear-trapped Survivin, could repair TMZ-induced DSBs and evaded senescence. Mass spectrometry-based interactomics revealed, however, no direct interaction of Survivin with any of the repair factors. The improved TMZ-triggered HR activity in Surv-GFP was associated with enhanced mRNA and stabilized RAD51 protein expression, opposite to diminished RAD51 expression in SurvNESmut cells. Notably, cytoplasmic Survivin could significantly compensate for the viability under RAD51 knockdown. Differential Survivin localization also resulted in distinctive TMZ-triggered transcriptional pathways, associated with senescence and chromosome instability as shown by global transcriptome analysis. Orthotopic LN229 xenografts, expressing SurvNESmut exhibited diminished growth and increased DNA damage upon TMZ, as manifested by PCNA and γH2AX foci expression, respectively, in brain tissue sections. Consequently, those mice lived longer. Although tumors of high-grade glioma patients expressed majorly nuclear Survivin, they exhibited rarely NES mutations which did not correlate with survival. Based on our in vitro and xenograft data, Survivin nuclear trapping would facilitate glioma response to TMZ.

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Replication Restart in Bacteria

Journal of Bacteriology ◽

10.1128/jb.00102-17 ◽

2017 ◽

Vol 199 (13) ◽

Cited By ~ 25

Author(s):

Bénédicte Michel ◽

Steven J. Sandler

Keyword(s):

Homologous Recombination ◽

Genome Stability ◽

Strand Break ◽

Replication Initiation ◽

Replication Forks ◽

Independent Manner ◽

Close Link ◽

Replication Restart

ABSTRACT In bacteria, replication forks assembled at a replication origin travel to the terminus, often a few megabases away. They may encounter obstacles that trigger replisome disassembly, rendering replication restart from abandoned forks crucial for cell viability. During the past 25 years, the genes that encode replication restart proteins have been identified and genetically characterized. In parallel, the enzymes were purified and analyzed in vitro, where they can catalyze replication initiation in a sequence-independent manner from fork-like DNA structures. This work also revealed a close link between replication and homologous recombination, as replication restart from recombination intermediates is an essential step of DNA double-strand break repair in bacteria and, conversely, arrested replication forks can be acted upon by recombination proteins and converted into various recombination substrates. In this review, we summarize this intense period of research that led to the characterization of the ubiquitous replication restart protein PriA and its partners, to the definition of several replication restart pathways in vivo, and to the description of tight links between replication and homologous recombination, responsible for the importance of replication restart in the maintenance of genome stability.

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Formation of a Tap/NXF1 Homotypic Complex Is Mediated through the Amino-Terminal Domain of Tap and Enhances Interaction with Nucleoporins

Molecular Biology of the Cell ◽

10.1091/mbc.e07-03-0255 ◽

2008 ◽

Vol 19 (1) ◽

pp. 327-338 ◽

Cited By ~ 11

Author(s):

Leah H. Matzat ◽

Stephen Berberoglu ◽

Lyne Lévesque

Keyword(s):

Nuclear Export ◽

Rna Binding ◽

Direct Interaction ◽

Nuclear Pore ◽

Amino Terminal ◽

Multimeric Complex ◽

Rna Export ◽

Amino Terminal Domain

Nuclear export of mRNAs is mediated by the Tap/Nxt1 pathway. Tap moves its RNA cargo through the nuclear pore complex by direct interaction with nucleoporin phenylalanine-glycine repeats. This interaction is strengthened by the formation of a Tap/Nxt1 heterodimer. We now present evidence that Tap can form a multimeric complex with itself and with other members of the NXF family. We also show that the homotypic Tap complex can interact with both Nxt1 and nucleoporins in vitro. The region mediating this oligomerization is localized to the first 187 amino acids of Tap, which overlaps with its RNA-binding domain. Removal of this domain greatly reduces the ability of Tap to bind nucleoporins in vitro and in vivo. This is the first report showing that the Tap amino terminus modulates the interaction of Tap with nucleoporins. We speculate that this mechanism has a regulatory role for RNA export independent of RNA binding.

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Recombineering in C. elegans: genome editing using in vivo assembly of linear DNAs

10.1101/050815 ◽

2016 ◽

Author(s):

Alexandre Paix ◽

Helen Schmidt ◽

Geraldine Seydoux

Keyword(s):

Dna Repair ◽

Homologous Recombination ◽

Genome Editing ◽

Strand Break ◽

Double Strand Break ◽

Template Switching ◽

C Elegans ◽

Repair Mechanisms

ABSTRACTRecombineering, the use of endogenous homologous recombination systems to recombine DNA in vivo, is a commonly used technique for genome editing in microbes. Recombineering has not yet been developed for animals, where non-homology-based mechanisms have been thought to dominate DNA repair. Here, we demonstrate that homology-dependent repair (HDR) is robust in C. elegans using linear templates with short homologies (~35 bases). Templates with homology to only one side of a double-strand break initiate repair efficiently, and short overlaps between templates support template switching. We demonstrate the use of single-stranded, bridging oligonucleotides (ssODNs) to target PCR fragments precisely to DSBs induced by CRISPR/Cas9 on chromosomes. Based on these findings, we develop recombineering strategies for genome editing that expand the utility of ssODNs and eliminate in vitro cloning steps for template construction. We apply these methods to the generation of GFP knock-in alleles and gene replacements without co-integrated markers. We conclude that, like microbes, metazoans possess robust homology-dependent repair mechanisms that can be harnessed for recombineering and genome editing.

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Proteasome Activator REGγ Enhances Coxsackieviral Infection by Facilitating p53 Degradation

Journal of Virology ◽

10.1128/jvi.00008-10 ◽

2010 ◽

Vol 84 (21) ◽

pp. 11056-11066 ◽

Cited By ~ 22

Author(s):

Guang Gao ◽

Jerry Wong ◽

Jingchun Zhang ◽

Ivy Mao ◽

Jayant Shravah ◽

...

Keyword(s):

Nuclear Export ◽

Rna Virus ◽

Direct Interaction ◽

Proteasome Inhibition ◽

Ubiquitin Proteasome System ◽

Proteasome Activator ◽

Protein Levels ◽

Cvb3 Infection

ABSTRACT Coxsackievirus B3 (CVB3) is a small RNA virus associated with diseases such as myocarditis, meningitis, and pancreatitis. We have previously demonstrated that proteasome inhibition reduces CVB3 replication and attenuates virus-induced myocarditis. However, the underlying mechanisms by which the ubiquitin/proteasome system regulates CVB replication remain unclear. In this study, we investigated the role of REGγ, a member of the 11S proteasome activator, in CVB3 replication. We showed that overexpression of REGγ promoted CVB3 replication but that knockdown of REGγ led to reduced CVB3 replication. We further demonstrated that REGγ-mediated p53 proteolysis contributes, as least in part, to the proviral function of REGγ. Although total protein levels of REGγ remained unaltered after CVB3 infection, virus infection induced a redistribution of REGγ from the nucleus to the cytoplasm, rendering an opportunity for a direct interaction of REGγ with viral proteins and/or host proteins (e.g., p53), which controls viral growth and thereby enhances viral infectivity. Further analyses suggested a potential modification of REGγ by SUMO following CVB3 infection, which was verified by both in vitro and in vivo sumoylation assays. Sumoylation of REGγ may play a role in its nuclear export during CVB3 infection. Taken together, our results present the first evidence that the host REGγ pathway is utilized and modified during CVB3 infection to promote efficient viral replication.

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Endogenous hydrogen sulfide sulfhydrates IKKβ at cysteine 179 to control pulmonary artery endothelial cell inflammation

Clinical Science ◽

10.1042/cs20190514 ◽

2019 ◽

Vol 133 (20) ◽

pp. 2045-2059 ◽

Cited By ~ 4

Author(s):

Da Zhang ◽

Xiuli Wang ◽

Siyao Chen ◽

Selena Chen ◽

Wen Yu ◽

...

Keyword(s):

Hydrogen Sulfide ◽

Endothelial Cell ◽

Pulmonary Artery ◽

Cell Model ◽

Site Directed Mutagenesis ◽

Critical Event ◽

Hypertensive Rats ◽

Pulmonary Artery Endothelial Cell

Abstract Background: Pulmonary artery endothelial cell (PAEC) inflammation is a critical event in the development of pulmonary arterial hypertension (PAH). However, the pathogenesis of PAEC inflammation remains unclear. Methods: Purified recombinant human inhibitor of κB kinase subunit β (IKKβ) protein, human PAECs and monocrotaline-induced pulmonary hypertensive rats were employed in the study. Site-directed mutagenesis, gene knockdown or overexpression were conducted to manipulate the expression or activity of a target protein. Results: We showed that hydrogen sulfide (H2S) inhibited IKKβ activation in the cell model of human PAEC inflammation induced by monocrotaline pyrrole-stimulation or knockdown of cystathionine γ-lyase (CSE), an H2S generating enzyme. Mechanistically, H2S was proved to inhibit IKKβ activity directly via sulfhydrating IKKβ at cysteinyl residue 179 (C179) in purified recombinant IKKβ protein in vitro, whereas thiol reductant dithiothreitol (DTT) reversed H2S-induced IKKβ inactivation. Furthermore, to demonstrate the significance of IKKβ sulfhydration by H2S in the development of PAEC inflammation, we mutated C179 to serine (C179S) in IKKβ. In purified IKKβ protein, C179S mutation of IKKβ abolished H2S-induced IKKβ sulfhydration and the subsequent IKKβ inactivation. In human PAECs, C179S mutation of IKKβ blocked H2S-inhibited IKKβ activation and PAEC inflammatory response. In pulmonary hypertensive rats, C179S mutation of IKKβ abolished the inhibitory effect of H2S on IKKβ activation and pulmonary vascular inflammation and remodeling. Conclusion: Collectively, our in vivo and in vitro findings demonstrated, for the first time, that endogenous H2S directly inactivated IKKβ via sulfhydrating IKKβ at Cys179 to inhibit nuclear factor-κB (NF-κB) pathway activation and thereby control PAEC inflammation in PAH.

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Defibrotide Inhibits Platelet Activation by Cathepsin G Released From Stimulated Polymorphonuclear Leukocytes

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648519 ◽

1992 ◽

Vol 67 (06) ◽

pp. 660-664 ◽

Cited By ~ 17

Author(s):

Virgilio Evangelista ◽

Paola Piccardoni ◽

Giovanni de Gaetano ◽

Chiara Cerletti

Keyword(s):

Platelet Activation ◽

Polymorphonuclear Leukocytes ◽

Direct Interaction ◽

Cathepsin G ◽

In Vivo Test ◽

Cell Functions ◽

Test Models ◽

Antithrombotic Effects

SummaryDefibrotide is a polydeoxyribonucleotide with antithrombotic effects in experimental animal models. Most of the actions of this drug have been observed in in vivo test models but no effects have been reported in in vitro systems. In this paper we demonstrate that defibrotide interferes with polymorphonuclear leukocyte-induced human platelet activation in vitro. This effect was not related to any direct interaction with polymorphonuclear leukocytes or platelets, but was due to the inhibition of cathepsin G, the main biochemical mediator of this cell-cell cooperation. Since cathepsin G not only induces platelet activation but also affects some endothelial cell functions, the anticathepsin G activity of defibrotide could help to explain the antithrombotic effect of this drug.

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β-elemene alleviates airway stenosis via the ILK/Akt pathway modulated by MIR143HG sponging miR-1275

Cellular & Molecular Biology Letters ◽

10.1186/s11658-021-00261-0 ◽

2021 ◽

Vol 26 (1) ◽

Author(s):

Guoying Zhang ◽

Cheng Xue ◽

Yiming Zeng

Keyword(s):

Cell Cycle ◽

Cell Viability ◽

Cell Model ◽

Protective Efficacy ◽

Rabbit Model ◽

Akt Pathway ◽

Loss Of Function ◽

Airway Stenosis

Abstract Background We have previously found that β-elemene could inhibit the viability of airway granulation fibroblasts and prevent airway hyperplastic stenosis. This study aimed to elucidate the underlying mechanism and protective efficacy of β-elemene in vitro and in vivo. Methods Microarray and bioinformatic analysis were used to identify altered pathways related to cell viability in a β-elemene-treated primary cell model and to construct a β-elemene-altered ceRNA network modulating the target pathway. Loss of function and gain of function approaches were performed to examine the role of the ceRNA axis in β-elemene's regulation of the target pathway and cell viability. Additionally, in a β-elemene-treated rabbit model of airway stenosis, endoscopic and histological examinations were used to evaluate its therapeutic efficacy and further verify its mechanism of action. Results The hyperactive ILK/Akt pathway and dysregulated LncRNA-MIR143HG, which acted as a miR-1275 ceRNA to modulate ILK expression, were suppressed in β-elemene-treated airway granulation fibroblasts; β-elemene suppressed the ILK/Akt pathway via the MIR143HG/miR-1275/ILK axis. Additionally, the cell cycle and apoptotic phenotypes of granulation fibroblasts were altered, consistent with ILK/Akt pathway activity. In vivo application of β-elemene attenuated airway granulation hyperplasia and alleviated scar stricture, and histological detections suggested that β-elemene's effects on the MIR143HG/miR-1275/ILK axis and ILK/Akt pathway were in line with in vitro findings. Conclusions MIR143HG and ILK may act as ceRNA to sponge miR-1275. The MIR143HG/miR-1275/ILK axis mediates β-elemene-induced cell cycle arrest and apoptosis of airway granulation fibroblasts by modulating the ILK/Akt pathway, thereby inhibiting airway granulation proliferation and ultimately alleviating airway stenosis.

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Double-targeting CDCA8 and E2F1 inhibits the growth and migration of malignant glioma

Cell Death and Disease ◽

10.1038/s41419-021-03405-4 ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Xiaoxiong Wang ◽

Heping Wang ◽

Jiajun Xu ◽

Xu Hou ◽

Haoqiang Zhan ◽

...

Keyword(s):

Malignant Glioma ◽

Malignant Tumors ◽

Disease Free Survival ◽

High Grade Glioma ◽

Poor Overall Survival ◽

Survival Prognosis ◽

Who Grade ◽

And Migration

AbstractHigh-grade glioma is the most common and aggressive primary brain tumor in adults with poor therapeutic efficiency and survival prognosis. Cell division cycle associated 8 (CDCA8) has been well known as a cell cycle regulator and tumor promotor in various malignant tumors. However, its biological role in glioma still remains unclear. Our results showed that high level of CDCA8 was significantly correlated with advanced WHO grade and poor overall survival and disease-free survival prognosis. In vitro and in vivo investigations demonstrated that CDCA8 promoted the glioma malignancy by promoting cell proliferation, cell migration, and inhibiting cell apoptosis. Moreover, we found its synergetic biological protein—E2F1 by the gene microarray chip. In this study, we revealed that CDCA8 synergized with E2F1 facilitated the proliferation and migration of glioma. In conclusion, our study provides a novel promising therapeutic targets and prognostic biomarkers for malignant glioma treatment.

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Generation of tetracycline-controllable CYP3A4-expressing Caco-2 cells by the piggyBac transposon system

Scientific Reports ◽

10.1038/s41598-021-91160-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Moe Ichikawa ◽

Hiroki Akamine ◽

Michika Murata ◽

Sumito Ito ◽

Kazuo Takayama ◽

...

Keyword(s):

Small Intestine ◽

Drug Absorption ◽

Cell Model ◽

Negative Effects ◽

Piggybac Transposon ◽

Drug Metabolizing Enzyme ◽

Metabolizing Enzyme ◽

Cyp3a4 Expression

AbstractCaco-2 cells are widely used as an in vitro intestinal epithelial cell model because they can form a monolayer and predict drug absorption with high accuracy. However, Caco-2 cells hardly express cytochrome P450 (CYP), a drug-metabolizing enzyme. It is known that CYP3A4 is the dominant drug-metabolizing enzyme in human small intestine. In this study, we generated CYP3A4-expressing Caco-2 (CYP3A4-Caco-2) cells and attempted to establish a model that can simultaneously evaluate drug absorption and metabolism. CYP3A4-Caco-2 cells were generated by piggyBac transposon vectors. A tetracycline-controllable CYP3A4 expression cassette (tet-on system) was stably transduced into Caco-2 cells, thus regulating the levels of CYP3A4 expression depending on the doxycycline concentration. The CYP3A4 expression levels in CYP3A4-Caco-2 cells cultured in the presence of doxycycline were similar to or higher than those of adult small intestine. The CYP3A4-Caco-2 cells had enough ability to metabolize midazolam, a substrate of CYP3A4. CYP3A4 overexpression had no negative effects on cell proliferation, barrier function, and P-glycoprotein activity in Caco-2 cells. Thus, we succeeded in establishing Caco-2 cells with CYP3A4 metabolizing activity comparable to in vivo human intestinal tissue. This cell line would be useful in pharmaceutical studies as a model that can simultaneously evaluate drug absorption and metabolism.

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The Pif1 helicase is actively inhibited during meiotic recombination which restrains gene conversion tract length

Nucleic Acids Research ◽

10.1093/nar/gkab232 ◽

2021 ◽

Author(s):

Dipti Vinayak Vernekar ◽

Giordano Reginato ◽

Céline Adam ◽

Lepakshi Ranjha ◽

Florent Dingli ◽

...

Keyword(s):

Gene Conversion ◽

Meiotic Recombination ◽

Strand Break ◽

Dna Helicase ◽

Clamp Loader ◽

Repair Synthesis ◽

Dna Repair Synthesis ◽

Gene Conversions

Abstract Meiotic recombination ensures proper chromosome segregation to form viable gametes and results in gene conversions events between homologs. Conversion tracts are shorter in meiosis than in mitotically dividing cells. This results at least in part from the binding of a complex, containing the Mer3 helicase and the MutLβ heterodimer, to meiotic recombination intermediates. The molecular actors inhibited by this complex are elusive. The Pif1 DNA helicase is known to stimulate DNA polymerase delta (Pol δ) -mediated DNA synthesis from D-loops, allowing long synthesis required for break-induced replication. We show that Pif1 is also recruited genome wide to meiotic DNA double-strand break (DSB) sites. We further show that Pif1, through its interaction with PCNA, is required for the long gene conversions observed in the absence of MutLβ recruitment to recombination sites. In vivo, Mer3 interacts with the PCNA clamp loader RFC, and in vitro, Mer3-MutLβ ensemble inhibits Pif1-stimulated D-loop extension by Pol δ and RFC-PCNA. Mechanistically, our results suggest that Mer3-MutLβ may compete with Pif1 for binding to RFC-PCNA. Taken together, our data show that Pif1’s activity that promotes meiotic DNA repair synthesis is restrained by the Mer3-MutLβ ensemble which in turn prevents long gene conversion tracts and possibly associated mutagenesis.

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