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Comparative Studies on Bulky DNA Damage Binding by Nucleotide Excision Repair Proteins Using Surface Plasmon Resonance, Differential Scanning Fluorometry, and DNase I Footprinting.

Nucleotide excision repair is a crucial cellular mechanism that ensures genomic stability, thereby preventing mutations that can lead to cancer. The human XPC and its yeast ortholog Rad4 protein complexes are central to this process and were the focus of the study. We used surface plasmon resonance and differential scanning fluorimetry to study the binding characteristics of XPC and Rad4 when bound to the bulky cluster di-FAAF-containing 55-mer duplex DNA. Our findings revealed that XPC binds 10 times more significant affinity to control and di-FAAF-modified DNA than Rad4 with greater protein-DNA interactions. Differential scanning fluorimetry indicates that Rad4 causes comparatively more significant conformational changes upon complexation with the damaged DNA. We conducted DNase I footprinting of the Rad4/DNA complex for the first time by determining the regions protected from DNase I digestion. The DNA at the lesion is entirely resistant to digestion by DNase I in the absence of Rad4 several nucleotides to the 3'-side of the first FAAF lesion. The lack of DNase I cleavage at the lesions did not change upon adding Rad4. However, in the presence of Rad4, a footprint is observed on the 7-nucleotide region (5'-TGGTGAT-3') of the complementary strand to the 3' side of the lesion.

Surface Plasmon Resonance

DNA Nanostructure Self-Assembly in an Aqueous Ionic Liquid Solution with Enhanced Stability and Target Binding Affinity.

DNA nanostructure-enabled functional constructs have shown potential to improve healthcare outcomes by offering advanced disease diagnostic and therapeutic strategies. Translating this potential of DNA nanostructure-based constructs to real life applications relies on maintaining and enhancing the structural integrity and functions of the surface-anchored moieties. In this study, we explored the possibility of utilizing choline dihydrogen phosphate (CDHP) solution, an aqueous solution of ionic liquid, to assemble DNA nanostructures of different sizes and complexities with enhanced biostability and ligand binding affinity. We show successful formation of the DNA nanostructures in aqueous CDHP solution using gel electrophoresis, atomic force microscopy (AFM), and circular dichroism (CD). Biostability assays reveal that the aqueous CDHP solution may provide passive protection to DNA nanostructures against DNase I and human serum for up to 48 h. We also demonstrate that this enhanced biostability arises both from the structural conformation imparted during CDHP-mediated folding and from the presence of free CDHP ions in the solution. Notably, removal of free ions reduced the passive protection effect, but did not eliminate it, indicating the contribution of both folding and surrounding free ions. Using flow cytometry and surface plasmon resonance assays, we show that the presence of aqueous CDHP solution can enhance the binding of aptamer-functionalized DNA nanostructures to specific receptors on acute myeloid leukemia (AML) cells. Our strategy of using ionic liquid solution for one-pot preparation with enhanced stability and functionality offers a robust, simpler and faster alternative for DNA nanostructure-based constructs.

Ionic Liquids

Efficient and precise programmable DNA knock-in without double-strand breaks.

Programmable gene knock-in holds substantial promise for treating genetic diseases and advancing cell therapies. However, achieving precise and efficient kilobase-scale DNA fragment integration remains challenging1,2. Here we report CRISPR kilobase-scale nickase-targeting (KNIT) editing for efficient, precise and programmable kilobase-scale DNA insertion without double-strand DNA cleavage, which is enabled through the coupling of a Cas9 nickase with a DNA donor recruiting system. KNIT editing facilitates programmable integration of DNA fragments from 0.7 kb to more than 10 kb and is effective across genomic loci and cell types. It achieves up to 89% efficiency and markedly reduces unintended insertion-deletion mutation (indels) rates, translocations and off-target editing. The system supports repeated insertion editing and multiloci gene knock-in with minimal translocations. Its enhanced version, KNIT editor 2, further improves efficiency via a single transfection. Moreover, in mutant cells with a pathological mutation, KNIT editing restores normal gene expression by inserting a therapeutic gene into a safe harbour locus or its native locus. Notably, KNIT editing enables non-viral and programmable chimeric antigen receptor T cell (CAR-T cell) engineering without double-strand breaks and with clinically relevant efficiencies. Moreover, the engineered CAR-T cells exhibit effective antitumour activity in vitro and in mouse models. Therefore, by achieving programmable and site-specific kilobase-scale DNA insertions without double-strand breaks while reducing unintended outcomes, KNIT editing provides a versatile platform for advancing personalized medicine.

Animals

The nontoxic cell cycle modulator indirubin augments transduction of adeno-associated viral vectors and zinc-finger nuclease-mediated gene targeting.

Parameters that regulate or affect the cell cycle or the DNA repair choice between non-homologous end-joining and homology-directed repair (HDR) are excellent targets to enhance therapeutic gene targeting. Here, we have evaluated the impact of five cell-cycle modulating drugs on targeted genome engineering mediated by DNA double-strand break (DSB)-inducing nucleases, such as zinc-finger nucleases (ZFNs). For a side-by-side comparison, we have established four reporter cell lines by integrating a mutated EGFP gene into either three transformed human cell lines or primary umbilical cord-derived mesenchymal stromal cells (UC-MSCs). After treatment with different cytostatic drugs, cells were transduced with adeno-associated virus (AAV) vectors that encode a nuclease or a repair donor to rescue EGFP expression through DSB-induced HDR. We show that transient cell-cycle arrest increased AAV transduction and AAV-mediated HDR up to six-fold in human cell lines and ten-fold in UC-MSCs, respectively. Targeted gene correction was observed in up to 34% of transduced cells. Both the absolute and the relative gene-targeting frequencies were dependent on the cell type, the cytostatic drug, the vector dose, and the nuclease. Treatment of cells with the cyclin-dependent kinase inhibitor indirubin-3'-monoxime was especially promising as this compound combined high stimulatory effects with minimal cytotoxicity. In conclusion, indirubin-3'-monoxime significantly improved AAV transduction and the efficiency of AAV/ZFN-mediated gene targeting and may thus represent a promising compound to enhance DSB-mediated genome engineering in human stem cells, such as UC-MSCs, which hold great promise for future clinical applications.

Blotting, Western

DiCARN-DNase: enhancing cell-to-cell Hi-C resolution using dilated cascading ResNet with self-attention and DNase-seq chromatin accessibility data.

MOTIVATION: The spatial organization of chromatin is fundamental to gene regulation and essential for proper cellular function. The Hi-C technique remains the leading method for unraveling 3D genome structures, but the limited availability of high-resolution (HR) Hi-C data poses significant challenges for comprehensive analysis. Deep learning models have been developed to predict HR Hi-C data from low-resolution counterparts. Early Convolutional Neural Network (CNN)-based models improved resolution but struggled with issues like blurring and capturing fine details. In contrast, Generative Adversarial Network (GAN)-based methods encountered difficulties in maintaining diversity and generalization. Additionally, most existing algorithms perform poorly in cross-cell line generalization, where a model trained on one cell type is used to enhance HR data in another cell type. RESULTS: In this work, we propose Dilated Cascading Residual Network (DiCARN) to overcome these challenges and improve Hi-C data resolution. DiCARN leverages dilated convolutions and cascading residuals to capture a broader context while preserving fine-grained genomic interactions. Additionally, we incorporate DNase-seq data into our model, providing a robust framework that demonstrates superior generalizability across cell lines in HR Hi-C data reconstruction. AVAILABILITY AND IMPLEMENTATION: DiCARN is publicly available at https://github.com/OluwadareLab/DiCARN.

Chromatin

Functional impact of Nth like DNA glycosylase 1 on mitochondrial dynamics.

Nth like DNA glycosylase 1 (NTHL1), a key base excision repair enzyme, has long been considered essential for nuclear and mitochondrial genome integrity. Combining in vitro biochemical assays, in cellulo molecular biology, and bioinformatic analyses, we investigated how NTHL1 loss affects mitochondrial DNA (mtDNA) stability and mitochondrial function. Contrary to the conventional view that mtDNA damage is solely detrimental, we find that NTHL1 loss confers a beneficial, mitochondria-initiated phenotype in human cells. Despite accumulating mtDNA lesions, NTHL1 loss unexpectedly increases mtDNA copy number, elevates oxidative phosphorylation protein levels, and enhances mitochondrial respiration. NTHL1-/- cells also show increased mitochondrial mass and higher levels of the biogenesis regulator PGC1α and the fusion protein OPA1, indicating an adaptive response that boosts mitochondrial function and capacity. Consequently, NTHL1-/- cells exhibit resistance to mitochondrial stress, accompanied by increased eIF2α phosphorylation and reduced MYC levels, converging on a broader transcriptional adaptive program. This phenotype depends on mitochondrial NTHL1 and reactive oxygen species (ROS) signaling, since treatment with ROS scavengers or mitochondria-specific reintroduction of NTHL1 rescues it. Together, these findings position NTHL1 as a key modulator of mtDNA stability and mitochondrial function, revealing that loss of this DNA repair enzyme shifts cellular metabolism toward a stress-adaptive state and enhances resilience to oxidative stress.

Humans

HEPARIN AND DNase I TREAT MYOCARDIAL INJURY IN SEPTIC MICE.

Background: Sepsis is a life-threatening clinical condition often seen in intensive care units, leading to multi-organ dysfunction. Myocardial injury is a prevalent complication, significantly increasing mortality among sepsis patients. Although heparin is used in sepsis management, its specific effects on myocardial injury and the role of neutrophil extracellular traps (NETs) in this context remain insufficiently understood. Aim: This study investigates the role of unfractionated heparin (UFH) combined with DNase I in reducing myocardial injury in a septic mouse model. Methods: A cecal ligation and puncture (CLP)-induced sepsis model was established in C57BL/6 mice to study myocardial injury. The experimental groups included treatments with UFH, UFH with DNase I, and NETs introduction. Myocardial injury was assessed using hematoxylin and eosin staining, enzyme linked immunosorbent assay for injury markers (creatine kinase MB [CK-MB] and lactate dehydrogenase [LDH]), and Western blotting for inflammatory proteins (TNF-α and IL-6). Differential proteomic analysis using data independent acquisition mass spectrometry and pathway enrichment analysis (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes) were conducted to identify molecular pathways and key proteins affected by the treatments. Results: Single UFH treatment increased the formation of NETs, upregulated TNF-α and IL-6, and increased CK-MB and LDH, worsening myocardial injury. The combination of UFH and DNase I significantly reduced myocardial injury, suppressing NETs formation and inflammation. Proteomic analysis identified crucial pathways related to NETs, metabolism, and complement and coagulation cascades, with proteins Ccn1 and Tagln highlighted as potential therapeutic targets. Conclusion: UFH combined with DNase I effectively alleviates myocardial injury in septic mice by modulating NETs formation and associated inflammatory processes. This study may provide new insights and options for the early use of heparin in the treatment of septic patients, particularly in cases with a higher risk of myocardial injury.

Animals

EndoV does not measurably affect TadA-dependent A-to-I RNA editing in Escherichia coli under exponential-growth conditions in rich medium.

Adenosine-to-inosine (A-to-I) mRNA editing changes the genetic information post-transcriptionally and was only recently reported to occur in bacteria. Here, we examined whether endonuclease V (EndoV; encoded by nfi) cleaves inosine-containing RNAs in vivo and thereby influences the abundance and fate of A-to-I-edited mRNAs in Escherichia coli. We generated an nfi loss-of-function mutant carrying a premature stop codon and performed RNA sequencing alongside the isogenic wild-type strain. We observed that global and site-specific editing occurrence or levels in both mRNAs and tRNAs were indistinguishable between strains. Moreover, overexpression of EndoV did not affect the number of edited sites, motif enrichment, or editing levels compared with a control strain overexpressing mCherry. Our findings suggest that, in contrast to human EndoV, bacterial EndoV does not regulate the steady-state pool of edited mRNAs in E. coli under nutrient-rich, exponential-growth conditions in vivo.IMPORTANCEAdenosine-to-inosine (A-to-I) mRNA editing is an emerging regulatory layer in bacteria, but the factors that act on edited transcripts are largely unknown. Endonuclease V (EndoV) was a prime candidate because it cleaves inosine-containing nucleic acids and can act on inosine-containing RNA in vitro. By combining loss-of-function and overexpression of EndoV with genome-wide RNA editing measurements, we show that EndoV does not measurably influence TadA-dependent A-to-I mRNA editing in Escherichia coli under standard laboratory conditions. This negative result is important because it rules out a natural effector candidate and redirects attention to other bacterial pathways that may process edited RNAs. Our work, therefore, sharpens mechanistic models for bacterial RNA editing and helps focus future searches for its regulators and physiological roles.

Escherichia coli

The association between vitamin D receptor gene polymorphism FokI and type 2 diabetic kidney disease and its molecular mechanism: a case control study.

BACKGROUND: The role of the vitamin D receptor single nucleotide polymorphism FOKI (VDR-FOKI) (rs2228570) in genetic susceptibility to type 2 diabetic kidney disease (T2DKD) remains uncertain. This study investigated the relationship between VDR-FOKI and T2DKD within the Chinese Plateau Han population and analyzed the underlying mechanisms. METHODS: A total of 316 subjects were enrolled, including 44 healthy adults, 114 individuals with type 2 diabetes mellitus (T2DM), and 158 patients with T2DKD. According to the 2023 American Diabetes Association Diabetes Guidelines, patients with T2DKD were categorized into low-medium-risk and high-risk groups based on estimates of glomerular filtration rate and urinary albumin-to-creatinine ratio. The VDR-FokI genotypes of all participants were identified using the Taqman probe and classified as homozygous mutant genotypes (C/C or FF), heterozygous mutant genotypes (C/T or Ff), and homozygous wild genotypes (T/T or ff). Plasma levels of malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase activity (SOD) were assessed in T2DKD patients with FF and ff genotypes. Additionally, the levels of plasma VDR, GPX4, and P53 were determined using ELISA, while the relative expressions of VDR mRNA, GPX4 mRNA, and TP53 mRNA in whole blood were measured by RT-qPCR. RESULTS: The T2DM patients with the ff genotype exhibited a 2.93-fold increased likelihood of developing T2DKD compared to those with the FF genotype (ORadjusted = 2.93; 95% CI: 1.142-7.513). Additionally, they were 2.01 times more likely to develop T2DKD than individuals with the FF and Ff genotypes (ORadjusted = 2.01; 95% CI: 1.008-4.006). However, no significant differences in VDR-FokI genotype distribution were observed between the healthy control group and the T2DM group, as well as between the low-medium-risk and high-risk groups of T2DKD. Furthermore, T2DKD patients with the ff genotype had significantly higher plasma levels of MDA compared to those with the FF genotype. In contrast, plasma GSH and SOD content was significantly lower in the ff genotype patients (P&#x2009;<&#x2009;0.05). Additionally, the GPX4 concentration in ff genotype patients was significantly lower than in FF genotype patients [14.88 (11.32,22.39) vs. 12.76 (8.55,13.75), P&#x2009;=&#x2009;0.037]. Nevertheless, no statistically significant difference was observed in the expression of VDRmRNA, GPX4mRNA, TP53mRNA, plasma VDR, and plasma P53. CONCLUSIONS: The ff genotype of VDR-FokI is a risk factor for T2DKD, and the potential mechanism may be related to ferroptosis. However, It is not associated with T2DM or the progression of T2DKD.

Humans