Terminal DNA Research Articles

Cu2O-Mediated Heterojunction Conversion from Dual Type II to Dual Z-Scheme: Its Application in Photoelectric-Colorimetric Dual-Mode Detection of Fat Mass and Obesity-Associated (FTO) Protein.

Although the construction of heterojunction has been used in photoelectrochemical (PEC) biosensors, their potential for tunable optical properties has not been deeply explored. Based on the fact that a type-II heterojunction and Z-scheme heterojunction have the same energy band structure, effective alteration of the electron transfer pathway has been achieved by introducing unique photoactive materials into the system and exploiting the interactions between the photomaterials. Based on this, we reported a novel polarity-switchable dual-mode sensor for fat mass and obesity-associated (FTO) protein analysis. Specifically, the MgIn2S4/Bi2MoO6/Bi2S3 dual type-II heterojunction was used as the sensing interface in concert with the rolling circle amplification, CRISPR/Cas12, and terminal DNA transfer enzyme multiamplification strategies, and finally, Cu2O was captured at the sensing interface. Due to the matched energy band, the introduction of Cu2O effectively changed the electron transfer pathway and realized the conversion from a dual type-II heterojunction to a dual Z-scheme heterojunction. It caused the switch of the photocurrent from the anode to the cathode. The developed PEC method showed high sensitivity and selectivity for FTO protein detection in the range of 0.0005-500 μg/L. In addition, based on the peroxidase-like activity of Cu2O to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2, the electrode system also achieved the colorimetric detection of FTO protein using the naked eye with the change of the color of the detection solution from colorless to blue. The detection range was from 0.05 to 500 μg/L. This work developed a photoelectrochemical-colorimetric biosensing platform with consciously designed semiconductor structures, revealing the potential of semiconductor-structured transformations in future sensing fields.

Transposable elements contribute to tissue-specific gene regulation in humans.

Transposable elements (TEs) contribute to approximately half of the human genome, and along with many other functions, they have been known to play a role in gene regulation in the genome. With TEs' active/repressed states varying across tissue and cell types, they have the potential to regulate gene expression in a tissue-specific manner. To provide a systematic analysis of TEs' contribution in tissue-specific gene regulation, we examined the regulatory elements and genes in association with TE-derived regulatory sequences in 14 human cell lines belonging to 10 different tissue types using the functional genomics data from the ENCODE project. Specifically, we separately analyzed regulatory regions identified by three different approaches (DNase hypersensitive sites (DHS), histone active sites (HA), and histone repressive sites (HR)). These regulatory regions showed to be distinct from each other by sharing less than 2.5% among all three types and more than 95% showed to be cell line-specific. Despite a lower total TE content overall than the genome average, each regulatory sequence type showed enrichment for one or two specific TE type(s): DHS for long terminal repeats (LTRs) and DNA transposons, HA for short interspersed nucleotide elements (SINEs), and HR for LTRs. In contrast, SINE was shown to be overrepresented in all three types of regulatory sequences located in gene-neighboring regions. TE-regulated genes were mostly shown to have cell line specific pattern, and tissue-specific genes (TSGs) showed higher usage of TE regulatory sequences in the tissue of their expression. While TEs in the regulatory sequences showed to be older than their genome-wide counterparts, younger TEs were shown to be more likely used in cell line specific regulatory sequences. Collectively, our study provided further evidence enforcing an important contribution of TEs to tissue-specific gene regulation in humans.

Semiarbitrary qPCR for Sensitive Detection of Circulating miRNA via Terminal Deoxynucleotidyl Transferase-Assisted RNA-Primed DNA Polymerization.

Circulating microRNAs (miRNAs) have recently emerged as noninvasive disease biomarkers. Quantitative detection of circulating miRNAs could offer significant information for clinical diagnosis due to its significance in the development of biological processes. In response to the current challenges of circulating miRNA detection, we introduce a sensitive, selective, and versatile circulating miRNA detection strategy using terminal deoxynucleotidyl transferase (TdT)-catalyzed RNA-primed DNA polymerization (TCRDP) coupled with semiarbitrary qPCR (SAPCR). Semiarbitrary qPCR was first developed here to detect long fragment targets with only a short-known sequence or to detect a short fragment target after extension with terminal transferase. Besides, the subsequent results show that TdT has a preference for RNA, particularly for extending RNAs with purine-rich and unstructured ends. Consequently, utilizing this assay, we have successfully applied it to the quantitative analysis of circulating miR-122 in animal models, a sensitive and informative biomarker for drug-induced liver injury, and as low as 200 zmol of the target is detected with desirable specificity and sensitivity, indicating that the TCRDP-SAPCR can offer a promising platform for nucleic acids analysis.

3D Super-Resolution Nuclear Q-FISH Imaging Reveals Cell-Cycle-Related Telomere Changes.

We present novel workflows for Q-FISH nanoscopy with the potential for prognostic applications and resolving novel chromatin compaction changes. DNA-fluorescence in situ hybridization (DNA-FISH) is a routine application to visualize telomeres, repetitive terminal DNA sequences, in cells and tissues. Telomere attrition is associated with inherited and acquired diseases, including cancer and cardiomyopathies, and is frequently analyzed by quantitative (Q)-FISH microscopy. Recently, nanoscopic imaging techniques have resolved individual telomere dimensions and their compaction as a prognostic marker, in part leading to conflicting conclusions still unresolved to date. Here, we developed a comprehensive Q-FISH nanoscopy workflow to assess telomeres with PNA telomere probes and 3D-Stimulated Emission Depletion (STED) microscopy combined with Dynamic Intensity Minimum (DyMIN) scanning. We achieved single-telomere resolution at high, unprecedented telomere coverage. Importantly, our approach revealed a decrease in telomere signal density during mitotic cell division compared to interphase. Innovatively expanding FISH-STED applications, we conducted double FISH targeting of both telomere- and chromosome-specific sub-telomeric regions and accomplished FISH-STED in human cardiac biopsies. In summary, this work further advanced Q-FISH nanoscopy, detected a new aspect of telomere compaction related to the cell cycle, and laid the groundwork for future applications in complex cell types such as post-mitotic neurons and muscle cells.

Combinatorial anticancer effects of multi metal ion and drug substitute with hydroxyapatite coatings on surgical grade 316LSS stainless steel alloys towards biomedical applications

The present study highlights the metal ions and existing drug ampicillin-loaded nano-hydroxyapatite (nHAP) coated on 316 stainless steel alloy (316LSS) using the electrodeposition method. In addition, the sample phase purity and crystallinity of the HAp composite coatings on 316LSS were analyzed by X-ray diffraction analysis (XRD) and Fourier transform infrared (FT-IR) spectroscopy using the KBr pellet method. The coating microstructure/morphology was characterized using a scanning electron microscope, which showed a flower-like morphology with the attachment of energy-dispersive X-ray spectroscopy (EDX) to confirm the major element groups in the synthesized sample. The TGA results showed that weight loss occurred in the temperature range of up to 800 °C for oxidation and reduction reactions. Additionally, the beat-optimized nanomaterial showed promising in vitro bioactivity against disease-causing microorganisms, displaying a significant zone of inhibition. Furthermore, cytotoxicity assessment using the MTT assay demonstrated that the synthesized samples effectively inhibited cell proliferation in human osteosarcoma cell lines (Saos-2). AO/EB double staining performed under a fluorescence microscope indicated changes in the morphology of the apoptotic cell nuclei. In addition, the relationship between ROS and nanomaterial-induced apoptosis in Saos-2 cells was analyzed by flow cytometry. MMP (ΔѰmt) profiling showed that the HAp composite increased the effective mitochondrial membrane damage or depolarization in the human osteosarcoma cell line. Moreover, the TUNEL assay suggested that treated nanomaterial with Saos-2 cells showed enhanced green fluorescence intensity, indicating terminal DNA damage. The obtained results meet the recommended physiological standard for synthesized 316LSS HAp composites to guide bone tissue regeneration.

DNA strand displacement and TdT-Mediated DNA extension for swift, convenient, and quantitative evaluation of sperm DNA integrity and its clinical implications

DNA integrity is crucial for the clinical pregnancy outcome and offspring health, while detection methods currently used (comet assay, TUNNEL assay, SCSA, etc.) can only provide the ratio of positive sperms at the cellular level and are unable to quantitatively detect the breakpoints at the DNA molecular level. Herein, we developed a detection system based on terminal deoxynucleotidyl transferase and DNA strand displacement fluorescent probe, which could efficiently and conveniently measure the number of 3′-OH (equivalent to the number of breakpoints). We further investigated the use of this technique in assisted reproduction after completing the principle verification, system optimization, and research on analytical performance. The detection system was shown to have a good linear range from 0.01 nM to 4 nM, using single-stranded DNA with 3′-OH end as the calibrator. The system underwent thorough optimization for stability and accuracy. In comparison to the widely accepted index DFI detected by SCSA, the new system demonstrated reasonable correlation and better prediction efficiency. Its applicability was also proven through its use in assisted reproductive technology procedures.

A Multibreed Genome-Wide Association Study for Cattle Leukocyte Telomere Length.

Telomeres are terminal DNA regions of chromosomes that prevent chromosomal fusion and degradation during cell division. In cattle, leukocyte telomere length (LTL) is associated with longevity, productive lifespan, and disease susceptibility. However, the genetic basis of LTL in this species is less studied than in humans. In this study, we utilized the whole-genome resequencing data of 239 animals from 17 cattle breeds for computational leukocyte telomere length estimation and subsequent genome-wide association study of LTL. As a result, we identified 42 significant SNPs, of which eight were found in seven genes (EXOC6B, PTPRD, RPS6KC1, NSL1, AGBL1, ENSBTAG00000052188, and GPC1) when using covariates for two major breed groups (Turano-Mongolian and European). Association analysis with covariates for breed effect detected 63 SNPs, including 13 in five genes (EXOC6B, PTPRD, RPS6KC1, ENSBTAG00000040318, and NELL1). The PTPRD gene, demonstrating the top signal in analysis with breed effect, was previously associated with leukocyte telomere length in cattle and likely is involved in the mechanism of alternative lengthening of telomeres. The single nucleotide variants found could be tested for marker-assisted selection to improve telomere-length-associated traits.

Terminal Alkyne-Modified DNA Aptamers with Enhanced Protein Binding Affinities.

Nucleic acid-based receptors, known as aptamers, are relatively fast to discover and manufacture but lack the diverse functional groups of protein receptors (e.g., antibodies). The binding properties of DNA aptamers can be enhanced by attaching abiotic functional groups; for example, aromatic groups such as naphthalene slow dissociation from proteins. Although the terminal alkyne is a π-electron-rich functional group that has been used in small molecule drugs to enhance binding to proteins through noncovalent interactions, it remains unexplored for enhancing DNA aptamer binding affinity. Here, we demonstrate the utility of the terminal alkyne for improving the binding of DNA to proteins. We prepared a library of 256 terminal-alkyne-bearing variants of HD22, a DNA aptamer that binds the protein thrombin with nanomolar affinity. After a one-step thrombin-binding selection, a high-affinity aptamer containing two alkynes was discovered, exhibiting 3.2-fold tighter thrombin binding than the corresponding unmodified sequence. The tighter binding was attributable to a slower rate of dissociation from thrombin (5.2-fold slower than HD22). Molecular dynamics simulations with enhanced sampling by Replica Exchange with Solute Tempering (REST2) suggest that the π-electron-rich alkyne interacts with an asparagine side chain N-H group on thrombin, forming a noncovalent interaction that stabilizes the aptamer-protein interface. Overall, this work represents the first case of terminal alkynes enhancing the binding properties of an aptamer and underscores the utility of the terminal alkyne as an atom economical π-electron-rich functional group to enhance binding affinity with minimal steric perturbation.

The allotetraploid horseradish genome provides insights into subgenome diversification and formation of critical traits

Polyploidization can provide a wealth of genetic variation for adaptive evolution and speciation, but understanding the mechanisms of subgenome evolution as well as its dynamics and ultimate consequences remains elusive. Here, we report the telomere-to-telomere (T2T) gap-free reference genome of allotetraploid horseradish (Armoracia rusticana) sequenced using a comprehensive strategy. The (epi)genomic architecture and 3D chromatin structure of the A and B subgenomes differ significantly, suggesting that both the dynamics of the dominant long terminal repeat retrotransposons and DNA methylation have played critical roles in subgenome diversification. Investigation of the genetic basis of biosynthesis of glucosinolates (GSLs) and horseradish peroxidases reveals both the important role of polyploidization and subgenome differentiation in shaping the key traits. Continuous duplication and divergence of essential genes of GSL biosynthesis (e.g., FMOGS-OX, IGMT, and GH1 gene family) contribute to the broad GSL profile in horseradish. Overall, the T2T assembly of the allotetraploid horseradish genome expands our understanding of polyploid genome evolution and provides a fundamental genetic resource for breeding and genetic improvement of horseradish.

Identification of cis-acting elements upstream of regR gene in streptococcus pneumoniae

The identification and characterization of functional cis-acting elements is of fundamental importance for comprehending the regulatory mechanisms of gene transcription and bacterial pathogenesis. The transcription factor RegR has been demonstrated to control both competence and virulence in Streptococcus pneumoniae. Despite the clear contribution of RegR to these pathways, the mechanisms underlying its transcriptional regulation remain poorly understood. In this study, we conducted mutational analysis, gene dissection and luciferase activity assays to characterize the cis-elements situated upstream of the regR gene. Our findings revealed that a 311 bp 3′-terminal DNA sequence of the spd0300 gene represents a central region of the upstream cis-acting element of regR. Further investigations identified two structurally similar enhancer-like sequences within this region which feature prominently in the regulation of regR transcription. Furthermore, employing DNA pull-down assays allowed us to enrich the trans-acting factors with the potential to interact with these cis-acting elements. Notably, we found that the competence regulator ComE was implicated in the regulation of regR transcription, a finding which was corroborated by electrophoretic mobility shift assays (EMSA) and quantitative real-time PCR analyses (qRT-PCR). Taken together, our data thus provide fresh insight into the transcriptional regulation of regR.

Retrotransposons hijack alt-EJ for DNA replication and eccDNA biogenesis.

Retrotransposons are highly enriched in the animal genome1-3. The activation of retrotransposons can rewrite host DNA information and fundamentally impact host biology1-3. Although developmental activation of retrotransposons can offer benefits for the host, such as against virus infection, uncontrolled activation promotes disease or potentially drives ageing1-5. After activation, retrotransposons use their mRNA as templates to synthesize double-stranded DNA for making new insertions in the host genome1-3,6. Although the reverse transcriptase that they encode can synthesize the first-strand DNA1-3,6, how the second-strand DNA is generated remains largely unclear. Here we report that retrotransposons hijack the alternative end-joining (alt-EJ) DNA repair process of the host for a circularization step to synthesize their second-strand DNA. We used Nanopore sequencing to examine the fates of replicated retrotransposon DNA, and found that 10% of them achieve new insertions, whereas 90% exist as extrachromosomal circular DNA (eccDNA). Using eccDNA production as a readout, further genetic screens identified factors from alt-EJ as essential for retrotransposon replication. alt-EJ drives the second-strand synthesis of the long terminal repeat retrotransposon DNA through a circularization process and is therefore necessary for eccDNA production and new insertions. Together, our study reveals that alt-EJ is essential in driving the propagation of parasitic genomic retroelements. Our study uncovers a conserved function of this understudied DNA repair process, and provides a new perspective to understand-and potentially control-the retrotransposon life cycle.

Stn1-Ten1 and Taz1 independently promote replication of subtelomeric fragile sequences in fission yeast

Efficient replication of terminal DNA is crucial to maintain telomere stability. In fission yeast, Taz1 and the Stn1-Ten1 (ST) complex play prominent roles in DNA-ends replication. However, their function remains elusive. Here, we have analyzed genome-wide replication and show that ST does not affect genome-wide replication but is crucial for the efficient replication of a subtelomeric region called STE3-2. We further show that, when ST function is compromised, a homologous recombination (HR)-based fork restart mechanism becomes necessary for STE3-2 stability. While both Taz1 and Stn1 bind to STE3-2, we find that the STE3-2 replication function of ST is independent of Taz1 but relies on its association with the shelterin proteins Pot1-Tpz1-Poz1. Finally, we demonstrate that the firing of an origin normally inhibited by Rif1 can circumvent the replication defect of subtelomeres when ST function is compromised. Our results help illuminate why fission yeast telomeres are terminal fragile sites.

Can circulating cell free DNA be a promising marker in ovarian cancer? – a genome-scale profiling study in a single institution

BackgroundCell-free DNA (cfDNA) is emerging as a potential biomarker for the detection of ovarian cancer (OC). Recently, we reported a method based upon cfDNA whole-genome sequencing data including the nucleosome distribution (nucleosome footprinting NF), terminal signature sequence (motif), DNA fragmentation (fragment), and copy number variation (CNV).In the present study, we explored whether multiomics early screening technology in cfDNA can be applied for early screening of ovarian cancer.MethodsFifty-nine patients with OC and 100 healthy controls were included in this prospective study. Cell-free DNA was extracted from plasma and analyzed by low-pass whole-genome sequencing. Genomic features were obtained for all samples of the cohort, including copy number variation (CNV), 5’-end motifs, fragmentation profiles, and nucleosome footprinting (NF). An integrated scoring system termed the OC score was developed based on the performance of these four features.ResultsAll four features showed diagnostic potential for OC. Based on the unique genome features of cfDNA, the OC score has high accuracy in distinguishing OC patients from healthy controls (AUC 97.7%; sensitivity 94.7%; specificity 98.0%) as a new comprehensive diagnostic method for OC. The OC score showed a gradual trend from healthy controls to OC patients with different stages, especially for early OC monitoring of concern, which achieved a satisfactory sensitivity (85.7%) at a high specificity.ConclusionsThis is the first study evaluating the potential of cell-free DNA for the diagnosis of primary OC using multidimensional early screening technology. We present a promising method to increase the accuracy of prediction in patients with OC.

Delphinidin induces autophagic flux blockage and apoptosis by inhibiting both multidrug resistance gene 1 and DEAD-box helicase 17 expressions in liver cancer cells.

To investigate the function and regulatory mechanisms of delphinidin in the treatment of hepatocellular carcinoma. HepG2 and HuH-7 cells were treated with different concentrations of delphinidin. Cell viability was analysed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The cell autophagy and autophagic flux were analysed by LC3b-green fluorescent protein (GFP)-Adv and LC3b-GFP-monomeric red fluorescent protein-Adv transfected HepG2 and HuH-7 cells, respectively. Cell apoptosis was analysed by Hoechst33342 staining, terminal deoxynucleotidyl transferase dUTP nick end labeling staining and DNA laddering. Cell autophagy, apoptosis and survival related protein expressions were detected by Western blotting. After treatment with different concentrations of delphinidin, the cell survival rate was significantly decreased. Delphinidin could block the autophagic flux, resulting in a significant increase in autophagosomes, and led to an increase in cell apoptosis. The combined application of delphinidin and cisplatin could promote the antitumour effect and reduce the dose of cisplatin in tumour cells. Further mechanism studies reveal that delphinidin could inhibit the multidrug resistance gene 1 (MDR1) and the tumour-promoting transcription cofactor DEAD-box helicase 17 (DDX17) expression in tumour cells. Overexpression of DDX17 could reverse delphinidin's antitumor function in tumour cells. Delphinidin has a strong anti-tumour effect by inducing tumour cell autophagic flux blockage and apoptosis by inhibiting of both MDR1 and DDX17 expression.

Two aspects of longevity are associated with rates of loss of telomeres in birds.

Telomeres, the terminal repetitive DNA sequences at the ends of linear chromosomes, have strong associations with longevity in some major taxa. Longevity has been linked to rate of decline in telomere length in birds and mammals, and absolute telomere length seems to be associated with body mass in mammals. Using a phylogenetic comparative method and 30 species of birds, we examined longevity (reflected by maximum lifespan), absolute telomere length, the rate of change in telomere length (TROC), and body mass (often strongly associated with longevity) to ascertain their degree of association. We divided lifespan into two life‐history components, one reflected by body size (measured as body mass) and a component that was statistically independent of body mass. While both lifespan and body mass were strongly associated with a family tree of the species (viz., the phylogeny of the species), telomere measures were not. Telomere length was not significantly associated with longevity or body mass or our measure of mass‐independent lifespan. TROC, however, was strongly associated with mass‐independent lifespan, but only to a much lesser degree at best with body mass‐predicted lifespan. Our results supported an association of TROC and longevity, in particular longevity that was independent of body size and part of the pace‐of‐life syndrome of life histories.

Analysis of microbial community diversity and physicochemical factors in pit mud of different ages based on high-throughput sequencing.

In this study, Illumina MiSeq/NovaSeq high-throughput sequencing technology was used to sequence the terminal DNA fragments of microbial communities in Wuliangye pit mud. The results showed that there were 5 dominant bacterial phyla and 13 dominant bacterial genera in the pit mud, which belonged to 4 phyla, mainly Firmicutes. There were 3 dominant fungal phyla and 5 dominant fungal genera in cellar mud, which belonged to 2 phyla and concentrated in Ascomycota. According to the statistical data, the low pH value cellar pool is more conducive to the enrichment of acid-resistant or acid-biased bacteria, which is the key to flavor formation. In addition, the components of ammonium nitrogen, available phosphorus and available potassium in pit mud need to be replenished in time. In addition, sampling time, fermentation time, temperature, and other external environments also have certain effects on microbial diversity and abundance in the pit. With the use of cellars, various types of microorganisms are constantly evolving to adapt to the environment inside the pits. The succession rule of microbe in pit mud was preliminarily revealed, which provided the basis for improving the quality and technical development of Wuliangye.

Self-assembling short immunostimulatory duplex RNAs with broad-spectrum antiviral activity

The current coronavirus disease 2019 (COVID-19) pandemic highlights the need for broad-spectrum antiviral therapeutics. Here we describe a new class of self-assembling immunostimulatory short duplex RNAs that potently induce production of type I and type III interferon (IFN-I and IFN-III). These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique sequence motif (sense strand, 5′-C; antisense strand, 3′-GGG) that mediates end-to-end dimer self-assembly. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases did not affect their ability to induce IFN. Unlike previously described immunostimulatory small interfering RNAs (siRNAs), their activity is independent of Toll-like receptor (TLR) 7/8, but requires the RIG-I/IRF3 pathway that induces a more restricted antiviral response with a lower proinflammatory signature compared with immunostimulant poly(I:C). Immune stimulation mediated by these duplex RNAs results in broad-spectrum inhibition of infections by many respiratory viruses with pandemic potential, including severe acute respiratory syndrome coronavirus (SARS-CoV)-2, SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), human coronavirus (HCoV)-NL63, and influenza A virus in cell lines, human lung chips that mimic organ-level lung pathophysiology, and a mouse SARS-CoV-2 infection model. These short double-stranded RNAs (dsRNAs) can be manufactured easily, and thus potentially could be harnessed to produce broad-spectrum antiviral therapeutics.

Construction of ssDNA-Attached LR-Chimera Involving Z-DNA for ZBP1 Binding Analysis.

The binding of proteins to Z-DNA is hard to analyze, especially for short non-modified DNA, because it is easily transferred to B-DNA. Here, by the hybridization of a larger circular single-stranded DNA (ssDNA) with a smaller one, an LR-chimera (involving a left-handed part and a right-handed one) with an ssDNA loop is produced. The circular ssDNAs are prepared by the hybridization of two ssDNA fragments to form two nicks, followed by nick sealing with T4 DNA ligase. No splint (a scaffold DNA for circularizing ssDNA) is required, and no polymeric byproducts are produced. The ssDNA loop on the LR-chimera can be used to attach it with other molecules by hybridization with another ssDNA. The gel shift binding assay with Z-DNA specific binding antibody (Z22) or Z-DNA binding protein 1 (ZBP1) shows that stable Z-DNA can form under physiological ionic conditions even when the extra ssDNA part is present. Concretely, a 5′-terminal biotin-modified DNA oligonucleotide complementary to the ssDNA loop on the LR-chimera is used to attach it on the surface of a biosensor inlaid with streptavidin molecules, and the binding constant of ZBP1 with Z-DNA is analyzed by BLI (bio-layer interferometry). This approach is convenient for quantitatively analyzing the binding dynamics of Z-DNA with other molecules.

Role of HSV-1 Capsid Vertex-Specific Component (CVSC) and Viral Terminal DNA in Capsid Docking at the Nuclear Pore.

Penetration of the viral genome into a host cell nucleus is critical for initiation of viral replication for most DNA viruses and a few RNA viruses. For herpesviruses, viral DNA ejection into a nucleus occurs when the capsid docks at the nuclear pore complex (NPC) basket with the correct orientation of the unique capsid portal vertex. It has been shown that capsid vertex-specific component (CVSC) proteins, which are located at the twelve vertices of the human herpes simplex virus type 1 (HSV-1) capsid, interact with nucleoporins (Nups) of NPCs. However, it remained unclear whether CVSC proteins determine capsid-to-NPC binding. Furthermore, it has been speculated that terminal DNA adjacent to the portal complex of DNA-filled C-capsids forms a structural motif with the portal cap (which retains DNA in the capsid), which mediates capsid-NPC binding. We demonstrate that terminal viral DNA adjacent to the portal proteins does not present a structural element required for capsid-NPC binding. Our data also show that level of CVSC proteins on the HSV-1 capsid affects level of NPC binding. To elucidate the capsid-binding process, we use an isolated, reconstituted cell nucleus system that recapitulates capsid-nucleus binding in vivo without interference from trafficking kinetics of capsids moving toward the nucleus. This allows binding of non-infectious capsid maturation intermediates with varying levels of vertex-specific components. This experimental system provides a platform for investigating virus–host interaction at the nuclear membrane.

Effects of Curcumin on Aging: Molecular Mechanisms and Experimental Evidence.

Aging is characterized by a progressive inability to maintain homeostasis, self-repair, renewal, performance, and fitness of different tissues throughout the lifespan. Senescence is occurring following enormous intracellular or extracellular stress stimuli. Cellular senescence serves as an antiproliferative process that causes permanent cell cycle arrest and restricts the lifespan. Senescent cells are characterized by terminal cell cycle arrest, enlarged lysosome, and DNA double-strand breaks as well as lipofuscin granularity, senescence-associated heterochromatin foci, and activation of DNA damage response. Curcumin, a hydrophobic polyphenol, is a bioactive chemical constituent of the rhizomes of Curcuma longa Linn (turmeric), which has been extensively used for the alleviation of various human disorders. In addition to its pleiotropic effects, curcumin has been suggested to have antiaging features. In this review, we summarized the therapeutic potential of curcumin in the prevention and delaying of the aging process.