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Nucleic Acids Research Jun 2024The replicative mitochondrial DNA polymerase, Polγ, and its protein regulation are essential for the integrity of the mitochondrial genome. The intricacies of Polγ...
The replicative mitochondrial DNA polymerase, Polγ, and its protein regulation are essential for the integrity of the mitochondrial genome. The intricacies of Polγ regulation and its interactions with regulatory proteins, which are essential for fine-tuning polymerase function, remain poorly understood. Misregulation of the Polγ heterotrimer, consisting of (i) PolG, the polymerase catalytic subunit and (ii) PolG2, the accessory subunit, ultimately results in mitochondrial diseases. Here, we used single particle cryo-electron microscopy to resolve the structure of PolG in its apoprotein state and we captured Polγ at three intermediates within the catalytic cycle: DNA bound, engaged, and an active polymerization state. Chemical crosslinking mass spectrometry, and site-directed mutagenesis uncovered the region of LonP1 engagement of PolG, which promoted proteolysis and regulation of PolG protein levels. PolG2 clinical variants, which disrupted a stable Polγ complex, led to enhanced LonP1-mediated PolG degradation. Overall, this insight into Polγ aids in an understanding of mitochondrial DNA replication and characterizes how machinery of the replication fork may be targeted for proteolytic degradation when improperly functioning.
PubMed: 38932681
DOI: 10.1093/nar/gkae539 -
Viruses Jun 2024Disease resistance gene (R gene)-encoded nucleotide-binding leucine-rich repeat proteins (NLRs) are critical players in plant host defence mechanisms because of their...
Disease resistance gene (R gene)-encoded nucleotide-binding leucine-rich repeat proteins (NLRs) are critical players in plant host defence mechanisms because of their role as receptors that recognise pathogen effectors and trigger plant effector-triggered immunity (ETI). This study aimed to determine the putative role of a cassava coiled-coil (CC)-NLR (CNL) gene () (single allele) located on chromosome 12 in the tolerance or susceptibility to South African cassava mosaic virus (SACMV), one of the causal agents of cassava mosaic disease (CMD). A transient protoplast system was used to knock down the expression of by clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR-Cas9). The -targeting CRISPR vectors and/or SACMV DNA A and DNA B infectious clones were used to transfect protoplasts isolated from leaf mesophyll cells from the SACMV-tolerant cassava () cultivar TME3. The CRISPR/Cas9 silencing vector significantly reduced expression in protoplasts whether with or without SACMV co-infection. Notably, SACMV DNA A replication was higher in protoplasts with lower expression levels than in non-silenced protoplasts. Mutagenesis studies revealed that protoplast co-transfection with CRISPR- silencing vector + SACMV and transfection with only SACMV induced nucleotide substitution mutations that led to altered amino acids in the highly conserved MHD motif of the -translated polypeptide. This may abolish or alter the regulatory role of the MHD motif in controlling R protein activity and could contribute to the increase in SACMV-DNA A accumulation observed in -silenced protoplasts. The results herein demonstrate for the first time a role for a CNL gene in tolerance to a geminivirus in TME3.
Topics: Manihot; Plant Diseases; Begomovirus; Virus Replication; Plant Proteins; Geminiviridae; CRISPR-Cas Systems; Disease Resistance; Protoplasts; Leucine-Rich Repeat Proteins
PubMed: 38932233
DOI: 10.3390/v16060941 -
Viruses Jun 2024Infectious spleen and kidney necrosis virus (ISKNV) infections can induce the process of host cellular autophagy but have rarely been identified within the molecular...
Infectious spleen and kidney necrosis virus (ISKNV) infections can induce the process of host cellular autophagy but have rarely been identified within the molecular autophagy signaling pathway. In the present study, we demonstrated that ISKNV induces ROS-mediated oxidative stress signals for the induction of 5'AMP-activated protein kinase/mechanistic target of rapamycin kinase (AMPK/mTOR)-mediated autophagy and upregulation of host antioxidant enzymes in fish GF-1 cells. We also examined ISKNV-induced oxidative stress, finding that reactive oxidative species (ROS) increased by 1.5-fold and 2.5-fold from day 2 to day 3, respectively, as assessed by the HDCFDA assay for tracing hydrogen peroxide (HO), which was blocked by NAC treatment in fish GF-1 cells. Furthermore, ISKNV infection was shown to trigger oxidative stress/Nrf2 signaling from day 1 to day 3; this event was then correlated with the upregulation of antioxidant enzymes such as Cu/ZnSOD and MnSOD and was blocked by the antioxidant NAC. Using an MDC assay, TEM analysis and autophagy marker LC3-II/I ratio, we found that ROS stress can regulate autophagosome formation within the induction of autophagy, which was inhibited by NAC treatment in GF-1 cells. Through signal analysis, we found that AMPK/mTOR flux was modulated through inhibition of mTOR and activation of AMPK, indicating phosphorylation levels of mTOR Ser 2448 and AMPK Thr 172 from day 1 to day 3; however, this process was reversed by NAC treatment, which also caused a reduction in virus titer (TCID) of up to 1000 times by day 3 in GF-1 cells. Thus, ISKNV-induced oxidative stress signaling is blocked by antioxidant NAC, which can also either suppress mTOR/AMPK autophagic signals or reduce viral replication. These findings may provide the basis for the creation of DNA control and treatment strategies.
Topics: Oxidative Stress; Autophagy; Virus Replication; Animals; TOR Serine-Threonine Kinases; Signal Transduction; Cell Line; AMP-Activated Protein Kinases; Antioxidants; Reactive Oxygen Species; NF-E2-Related Factor 2
PubMed: 38932206
DOI: 10.3390/v16060914 -
Viruses May 2024Tripartite motif (TRIM) proteins, comprising a family of over 100 members with conserved motifs, exhibit diverse biological functions. Several TRIM proteins influence...
Tripartite motif (TRIM) proteins, comprising a family of over 100 members with conserved motifs, exhibit diverse biological functions. Several TRIM proteins influence viral infections through direct antiviral mechanisms or by regulating host antiviral innate immune responses. To identify TRIM proteins modulating hepatitis B virus (HBV) replication, we assessed 45 human TRIMs in HBV-transfected HepG2 cells. Our study revealed that ectopic expression of 12 TRIM proteins significantly reduced HBV RNA and subsequent capsid-associated DNA levels. Notably, TRIM65 uniquely downregulated viral pregenomic (pg) RNA in an HBV-promoter-specific manner, suggesting a targeted antiviral effect. Mechanistically, TRIM65 inhibited HBV replication primarily at the transcriptional level via its E3 ubiquitin ligase activity and intact B-box domain. Though HNF4α emerged as a potential TRIM65 substrate, disrupting its binding site on the HBV genome did not completely abolish TRIM65's antiviral effect. In addition, neither HBx expression nor cellular MAVS signaling was essential to TRIM65-mediated regulation of HBV transcription. Furthermore, CRISPR-mediated knock-out of TRIM65 in the HepG2-NTCP cells boosted HBV infection, validating its endogenous role. These findings underscore TRIM proteins' capacity to inhibit HBV transcription and highlight TRIM65's pivotal role in this process.
Topics: Humans; Hepatitis B virus; Hep G2 Cells; Tripartite Motif Proteins; Virus Replication; Ubiquitin-Protein Ligases; Transcription, Genetic; Hepatitis B; Promoter Regions, Genetic; RNA, Viral
PubMed: 38932182
DOI: 10.3390/v16060890 -
Viruses May 2024Newcastle disease virus (NDV) is an avian pathogen with an unsegmented negative-strand RNA genome that belongs to the Paramyxoviridae family. While primarily pathogenic... (Review)
Review
Newcastle disease virus (NDV) is an avian pathogen with an unsegmented negative-strand RNA genome that belongs to the Paramyxoviridae family. While primarily pathogenic in birds, NDV presents no threat to human health, rendering it a safe candidate for various biomedical applications. Extensive research has highlighted the potential of NDV as a vector for vaccine development and gene therapy, owing to its transcriptional modularity, low recombination rate, and lack of a DNA phase during replication. Furthermore, NDV exhibits oncolytic capabilities, efficiently eliciting antitumor immune responses, thereby positioning it as a promising therapeutic agent for cancer treatment. This article comprehensively reviews the biological characteristics of NDV, elucidates the molecular mechanisms underlying its oncolytic properties, and discusses its applications in the fields of vaccine vector development and tumor therapy.
Topics: Newcastle disease virus; Animals; Humans; Genetic Vectors; Neoplasms; Oncolytic Virotherapy; Oncolytic Viruses; Genetic Therapy; Viral Vaccines; Newcastle Disease; Vaccine Development
PubMed: 38932177
DOI: 10.3390/v16060886 -
Viruses May 2024Alphabaculoviruses are lethal dsDNA viruses of Lepidoptera that have high genetic diversity and are transmitted in aggregates within proteinaceous occlusion bodies. This...
Alphabaculoviruses are lethal dsDNA viruses of Lepidoptera that have high genetic diversity and are transmitted in aggregates within proteinaceous occlusion bodies. This mode of transmission has implications for their efficacy as biological insecticides. A Nicaraguan isolate of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV-NIC) comprising nine genotypic variants has been the subject of considerable study due to the influence of variant interactions on the insecticidal properties of mixed-variant occlusion bodies. As part of a systematic study on the replication and transmission of variant mixtures, a tool for the accurate quantification of a selection of genotypic variants was developed based on the quantitative PCR technique (qPCR). First, primer pairs were designed around a region of high variability in four variants named SfNic-A, SfNic-B, SfNic-C and SfNic-E to produce amplicons of 103-150 bp. Then, using cloned purified amplicons as standards, amplification was demonstrated over a dynamic range of 10-10 copies of each target. The assay was efficient (mean ± SD: 98.5 ± 0.8%), reproducible, as shown by low inter- and intra-assay coefficients of variation (<5%), and specific to the target variants (99.7-100% specificity across variants). The quantification method was validated on mixtures of genotype-specific amplicons and demonstrated accurate quantification. Finally, mixtures of the four variants were quantified based on mixtures of budded virions and mixtures of DNA extracted from occlusion-derived virions. In both cases, mixed-variant preparations compared favorably to total viral genome numbers by quantification of the () gene that is present in all variants. This technique should prove invaluable in elucidating the influence of variant diversity on the transmission and insecticidal characteristics of this pathogen.
Topics: Nucleopolyhedroviruses; Animals; Spodoptera; Genotype; Genetic Variation; Real-Time Polymerase Chain Reaction; DNA, Viral
PubMed: 38932173
DOI: 10.3390/v16060881 -
Viruses May 2024The HIV-1 nucleocapsid protein (NC) is a multifunctional viral protein necessary for HIV-1 replication. Recent studies have demonstrated that reverse transcription (RT)...
The HIV-1 nucleocapsid protein (NC) is a multifunctional viral protein necessary for HIV-1 replication. Recent studies have demonstrated that reverse transcription (RT) completes in the intact viral capsid, and the timing of RT and uncoating are correlated. How the small viral core stably contains the ~10 kbp double stranded (ds) DNA product of RT, and the role of NC in this process, are not well understood. We showed previously that NC binds and saturates dsDNA in a non-specific electrostatic binding mode that triggers uniform DNA self-attraction, condensing dsDNA into a tight globule against extending forces up to 10 pN. In this study, we use optical tweezers and atomic force microscopy to characterize the role of NC's basic residues in dsDNA condensation. Basic residue mutations of NC lead to defective interaction with the dsDNA substrate, with the constant force plateau condensation observed with wild-type (WT) NC missing or diminished. These results suggest that NC's high positive charge is essential to its dsDNA condensing activity, and electrostatic interactions involving NC's basic residues are responsible in large part for the conformation, size, and stability of the dsDNA-protein complex inside the viral core. We observe DNA re-solubilization and charge reversal in the presence of excess NC, consistent with the electrostatic nature of NC-induced DNA condensation. Previous studies of HIV-1 replication in the presence of the same cationic residue mutations in NC showed significant defects in both single- and multiple-round viral infectivity. Although NC participates in many stages of viral replication, our results are consistent with the hypothesis that cationic residue mutations inhibit genomic DNA condensation, resulting in increased premature capsid uncoating and contributing to viral replication defects.
Topics: HIV-1; Reverse Transcription; DNA, Viral; gag Gene Products, Human Immunodeficiency Virus; Humans; Cations; Virus Replication; Microscopy, Atomic Force; Virion; Mutation
PubMed: 38932164
DOI: 10.3390/v16060872 -
Viruses May 2024In virology, the term reverse genetics refers to a set of methodologies in which changes are introduced into the viral genome and their effects on the generation of... (Review)
Review
In virology, the term reverse genetics refers to a set of methodologies in which changes are introduced into the viral genome and their effects on the generation of infectious viral progeny and their phenotypic features are assessed. Reverse genetics emerged thanks to advances in recombinant DNA technology, which made the isolation, cloning, and modification of genes through mutagenesis possible. Most virus reverse genetics studies depend on our capacity to rescue an infectious wild-type virus progeny from cell cultures transfected with an "infectious clone". This infectious clone generally consists of a circular DNA plasmid containing a functional copy of the full-length viral genome, under the control of an appropriate polymerase promoter. For most DNA viruses, reverse genetics systems are very straightforward since DNA virus genomes are relatively easy to handle and modify and are also (with few notable exceptions) infectious per se. This is not true for RNA viruses, whose genomes need to be reverse-transcribed into cDNA before any modification can be performed. Establishing reverse genetics systems for members of the has proven exceptionally challenging due to the low number of members of this family that propagate in cell culture. Despite the early successful rescue of calicivirus from a genome-length cDNA more than two decades ago, reverse genetics methods are not routine procedures that can be easily extrapolated to other members of the family. Reports of calicivirus reverse genetics systems have been few and far between. In this review, we discuss the main pitfalls, failures, and delays behind the generation of several successful calicivirus infectious clones.
Topics: Reverse Genetics; Caliciviridae; Genome, Viral; Animals; Humans; Virus Replication
PubMed: 38932159
DOI: 10.3390/v16060866 -
Viruses May 2024The devastating effects of COVID-19 have highlighted the importance of prophylactic and therapeutic strategies to combat respiratory diseases. Stimulator of interferon...
The devastating effects of COVID-19 have highlighted the importance of prophylactic and therapeutic strategies to combat respiratory diseases. Stimulator of interferon gene (STING) is an essential component of the host defense mechanisms against respiratory viral infections. Although the role of the cGAS/STING signaling axis in the innate immune response to DNA viruses has been thoroughly characterized, mounting evidence shows that it also plays a key role in the prevention of RNA virus infections. In this study, we investigated the role of STING activation during Influenza virus (IFV) infection. In both mouse bone marrow-derived macrophages and monocytic cell line THP-1 differentiated with PMA, we found that dimeric amidobenzimidazole (diABZI), a STING agonist, had substantial anti-IFV activity against multiple strains of IFV, including A/H1N1, A/H3N2, B/Yamagata, and B/Victoria. On the other hand, a pharmacological antagonist of STING (H-151) or the loss of STING in human macrophages leads to enhanced viral replication but suppressed IFN expression. Furthermore, diABZI was antiviral against IFV in primary air-liquid interface cultures of nasal epithelial cells. Our data suggest that STING agonists may serve as promising therapeutic antiviral agents to combat IFV.
Topics: Animals; Humans; Immunity, Innate; Mice; Antiviral Agents; Macrophages; Membrane Proteins; THP-1 Cells; Virus Replication; Influenza, Human; Dogs; Mice, Inbred C57BL; Orthomyxoviridae Infections; Orthomyxoviridae; Benzimidazoles; Signal Transduction
PubMed: 38932148
DOI: 10.3390/v16060855 -
Viruses May 2024Viruses exploit the host cell machinery to enable infection and propagation. This review discusses the complex landscape of DNA virus-host interactions, focusing... (Review)
Review
Viruses exploit the host cell machinery to enable infection and propagation. This review discusses the complex landscape of DNA virus-host interactions, focusing primarily on herpesviruses and adenoviruses, which replicate in the nucleus of infected cells, and vaccinia virus, which replicates in the cytoplasm. We discuss experimental approaches used to discover and validate interactions of host proteins with viral genomes and how these interactions impact processes that occur during infection, including the host DNA damage response and viral genome replication, repair, and transcription. We highlight the current state of knowledge regarding virus-host protein interactions and also outline emerging areas and future directions for research.
Topics: Humans; Genome, Viral; Virus Replication; DNA, Viral; Host-Pathogen Interactions; DNA Viruses; Animals; Viral Proteins; Herpesviridae; Vaccinia virus
PubMed: 38932138
DOI: 10.3390/v16060845