Efficient Repair Research Articles

Zinc Oxide Nanoparticles Incorporated in Poly-Hydroxyethyl Methacrylate/Acrylamide Membrane Trigger the Key Events of Full-Thickness Wound Healing in a Rabbit Model.

Zinc oxide nanoparticles are known to possess anti-inflammatory, antibacterial, and antiseptic properties and find wide application in the preparation of topical ointments. Wound dressings in the form of hydrogels can replenish the wound microenvironment to aid the healing process in a multidimensional way. We have fabricated a composite hydrogel using 1-3 wt. % ZnO nano-particles, synthesized by chelation reaction, and poly-2-hydroxyethyl methacrylate (pHEMA)/acrylamide, synthesized, and co-polymerized in 8 kGy gamma irradiation. Developed powders and composite membranes have been thoroughly analyzed for XRD, FTIR, SEM-EDX mapping, DTA/TGA, particle size, shape, morphology, porosity, water uptake, and contact angle. Thermally stable phase-pure ZnO spherical nanoparticles with an average crystallite size of 40 ± 2 nm have been used for fabricating well-dispersed composite with contact angle varying 78o-88o. These membranes, when used invivo, rendered a suitable environment conducive to tissue regeneration and ECM component deposition sequentially. Endowed with antibacterial properties, these hydrogels also demonstrated excelling swelling capacity which proved beneficial in maintaining a moist wound environment aiding in the healing process. An earlier wound closure was achieved with 2%-3% ZnO-pHEMA/acrylamide hydrogels which demonstrate the potential of ZnO nanoparticles in signaling and instructing the wound bed milieu towards the efficient repair.

Hydrogels in Alveolar Bone Regeneration.

Alveolar bone defects caused by oral trauma, alveolar fenestration, periodontal disease, and congenital malformations can severely affect oral function and facial aesthetics. Despite the successful clinical applications of bone grafts or bone substitutes, optimal alveolar bone regeneration continues to be challenging due to the complex oral environment and its unique physiological functions. Hydrogels that serve as promising candidates for tissue regeneration are under development to meet the specific needs for increased bone regeneration capacity and improved operational efficiency in alveolar bone repair. In this review, we emphasize the considerations in hydrogel design for alveolar bone regeneration and summarize the latest applications of hydrogels in prevalent clinical diseases related to alveolar bone defects. The future perspectives and challenges for the application of hydrogels in the field of alveolar bone regeneration are also discussed. Deepening our understanding of these biomaterials will facilitate the advent of novel inventions to improve the outcome of alveolar bone tissue regeneration.

Experimental Investigations on Repair and Permeability Reduction for Single Sandstone Fracture Using a Mixed CaCO3 and Fe(OH)3 Precipitate

In China, groundwater loss caused by underground coal mining is becoming increasingly serious. The key to groundwater restoration is to repair mining-induced water-conducting fractures (WCFs) in the overlying strata. In this study, the adsorption–consolidation sealing characteristics of chemical precipitates were used to conduct permeability reduction (PR) experiments, including adding mixed CaCO3 and Fe(OH)3 to a sandstone specimen with a single fracture at room temperature. An aqueous solution of Na2CO3 was used as the simulated groundwater, and a solution of mixed CaCl2 and FeCl2 was used as the repair reagent to simulate the water seepage conditions of a fractured rock mass. The two aqueous solutions were simultaneously injected into a single-fractured rock specimen at a constant flow rate. The experimental results show that the Fe(OH)3 colloid encapsulated CaCO3 crystals in a mixed precipitate, reducing the overall structural stability of the mixed precipitate and restricting repair and PR efficiency. However, the Fe(OH)3 precipitate had better PR efficiency in the initial stage of the experiment. Therefore, a better scheme was put forward to repair the WCF, utilizing a mixed Fe(OH)3 and CaCO3 precipitate with a molar ratio close to 1:4 in the early stage and a single CaCO3 precipitate in the later stage.

Ranking of power grid facilities as a tool for choosing a repair management system

In the long-term planning of repairs at power grid facilities in conditions of limited operational and investment resources, it is important to determine the "points of maximum return", that is, the objects whose repair will cause the greatest effect in terms of the company's target priorities. This requires an operational assessment and ranking of electric grid facilities, taking into account the technological and resource characteristics of the energy company. The article presents a decision-making methodology that, based on operational calculations and priority assessment, enables to identify power grid facilities with the highest repair efficiency in the sense of criteria characterizing the strategic goals of asset management of an energy company. The methodology combines methods of modeling and calculating the probabilities of failure in consumer power supply systems (PSS) with the determination of indices of the technical condition of equipment, methods for calculating labor costs for maintaining and restoring reliability and assessing damage from its disruptions.The developed methodology allows the energy company — the owner of assets, when choosing the most effective repair management system according to enlarged indicators and simplified models, to form prioritization lists of objects for which the critical repair rank corresponds to its strategic priorities. The possibility of cost estimation of the total labor costs for the maintenance of facilities for each of the received prioritization lists in comparison with the repair fund stated by the energy company expands the scope of the methodology and increases the validity of the decisions made. The methodology has been verified and confirmed by consideration on the example of a real PSS of oil fields using up-to-date operational information.

Effect of PI3-kinase inhibitors on DNA double strand break repair pathways: observations using a site specific DSB induction system.

We established two types of site-specific DNA double strand breaks (DSB) induction systems to elucidate factors which affect the efficiency or quality of DSB repair. For mutation assays, a site specific DSB was generated by the transient expression of a zinc finger nuclease which targets the human HPRT1 gene. A cell line in which time and site specific DSBs can be generated in a HR reporter construct was used for homology-directed repair (HR) analysis. By using these two systems, we investigated the effects of PI3-kinase inhibitors on the efficiency and quality of DSB repair. Ataxia telangiectasia mutated (ATM) kinase inhibition resulted a decrease in mutant frequency and a slight increase in deletion-type mutations accompanied by microhomology. Furthermore, the HR frequency increased significantly when ATM kinase activity was inhibited. Thus, ATM kinase activity might be involved in the suppression of DSB end resection, and this may promote DSB repair through canonical non-homologous end joining.

Design and evaluation of a novel variable-length stepped scarf repair technique using a cohesive damage model

The advantages of Carbon Fibre Reinforced Polymers (CFRPs) are well established, but repairing CFRP components remains difficult and costly, posing challenges for industries like aerospace. This paper explores the design, modelling, inspection, and testing of a Variable Length Stepped Scarf (VLSS) repair scheme for highly loaded composite structures. A fully nonlinear 2D Finite Element Model (FEM) is used to design the VLSS repair, predict failure loads and modes, and model adhesive cohesion and delamination. The model incorporates a validated progressive damage model, general contact, and both force and geometric nonlinearities. Two manufacturing techniques involving hard repair patches and glass beads to maintain a constant bond line are employed. A 3D FEM validated against repaired composite coupons under uniaxial tension shows excellent agreement with experimental data. The static strength repair efficiency is approximately 80 % of a pristine sample, with failure displacements at 87 %, and Hooke's stiffness at 102 % of pristine laminates. Cohesive failure at adhesive overlap edges is identified as the cause of stiffness degradation, confirming experimental observations. This study contributes to both composite repair modelling and repair design optimisation.

STEM-03. TARGETING F-ACTIN DYNAMICS OF GLIOBLASTOMAS TO OVERCOME THERAPY RESISTANCE: IMPACTS ON DNA REPAIR AND GLIOMA STEM CELL PHENOTYPE

Abstract Glioblastoma (GBM) is a highly aggressive brain tumor with high recurrence and resistance to therapies. The F-actin cytoskeleton in GBM is related to cell invasion and the glioma stem cell (GSC) phenotype, affecting self-renewal and migration. Our research identifies a novel role for the F-actin pathway in DNA repair, impacting genomic stability and contributing to therapy resistance. Understanding F-actin’s role is crucial for developing targeted strategies to improve GBM treatment outcomes. This study examines the effects of pharmacological F-actin depolymerization on reversing resistance to ionizing radiation (IR) and temozolomide (TMZ) in GBM spheroids. We established resistant sublines of GBM U87-MG cells through IR and TMZ cycles, observing significant resistance increases via MTT assays. Also, resistant cells had enhanced spheroid formation capacity, with higher size and proliferation. Alterations in DNA repair and F-actin pathway were observed, with intensified and disorganized F-actin polymerization and efficient repair in resistant cells. Elevated expression of stemness markers (Nestin, CD133, and CD44) indicated a GSC-like phenotype in resistant cells, corroborated by increased tumorigenicity and de novo spheroid formation. These markers were further enhanced by DNA damage. Treating cells with actin polymerization inhibitors reduced resistance to TMZ and IR, partly due to impaired DNA repair capacity. Additionally, F-actin disassembly affected stemness marker expression, reinforcing the link between cytoskeletal dynamics and the GSC phenotype. Our findings suggest that F-actin dynamic is crucial for resistance in GBM. Targeting F-actin could resensitize recurrent GBM tumours by diminishing DNA repair capabilities and affecting the GSC-like phenotype, offering new therapeutic avenues.

DNAR-08. THY1 MEDIATES TREATMENT RESISTANCE IN GLIOBLASTOMA THROUGH RAPID REPAIR OF DNA DAMAGE

Abstract Glioblastoma (GBM) is a uniformly lethal primary intracranial neoplasm that inevitably recurs despite treatment by DNA damaging agents radiation (RT) and temozolomide (TMZ). Recurrence may be driven by inherently resistant glioma stem-like cells (GSCs). GSCs have been shown to have constitutive upregulation of DNA damage response (DDR) pathways, resulting from elevated DNA replication stress. This baseline elevated DDR has consequently been shown to confer inherent resistance to DNA damaging agents, TMZ/RT. However, factors mediating elevated replication stress and upregulated DDR in GSCs are poorly defined. Previously, we identified the cell-surface protein, THY1, as a mediator of GSC phenotype and treatment resistance in GBM. To determine mechanisms mediating treatment resistance in THY1+ cells, we engineered patient-derived neurosphere and organoid models, to either overexpress or silence THY1 expression. These models were treated with RT and collected at various time points to measure DNA repair efficiency by assessing the formation and resolution of yH2AX foci and ATM/ATR activation. In parallel, patient-derived GBM tissue from over 20 patients was analyzed using single cell RNA sequencing and spatial transcriptomics to assess pathways associated with THY1 expression. Interestingly, spatial transcriptomics and single cell RNA sequencing data demonstrates significant upregulation of GSC pathways, as well as constitutive upregulation of DDR pathways (p<2e-16) in THY1-high cells. Exploiting our patient-derived lines we determined that DNA repair activation was upregulated at baseline, measured using yH2AX foci and immunoblotting. We then measured DDR in response to radiation and found that high THY1 expression mediated rapid repair of DNA. Overall, we demonstrate that THY1 mediates therapy resistance by constitutively upregulating DDR, likely by upregulating DNA replication stress. We are now working to determine the mechanisms mediating the GSC phenotype and DNA replication stress in THY1 cells in hopes of future translation.

The radiosensitivity of niraparib tosylate to esophageal squamous cell carcinoma is stronger under hypoxia and higher-pressure conditions

Background: Radiotherapy is an effective method for esophageal squamous cell carcinoma (ESCC) treatment show reduced effectiveness in long-term due to reduced sensitivity of cancer cells to radiotherapy. Niraparib tosylate, a poly ADP-ribose polymerase (PARP) inhibitor may enhance the radiosensitivity of these cells. Hence, the present study was aimed to study the effects of niraparib tosylate on ESCC proliferation, apoptosis and cell cycle along with radiosensitivity enhancement efficiency. Materials and methods: ESCC cell lines, KYSE-30 were subjected to niraparib tosylate or irradiation treatments or combination of both. CCK8 and colony formation assays were performed to monitor cell growth status. Cell cycle and apoptosis level were investigated through flow cytometry. The expressions of targeted genes were detected at protein levels by western blot. Besides, xenografts were successfully established in immunocompromised mice. Student’s t-test was used to compare data and P < 0.05 was considered statistically significant. Results: Treatment with niraparib tosylate showed G2/M cycle arrest and apoptosis in KYSE-30 cells and the rate was observed to be more significant with combination therapy. These effects were further strengthened when cells were cultured under hypoxia and high atmospheric pressure. An enhanced susceptibility to radiotherapy was observed with niraparib tosylate combination. The homologous recombination related regulator, Rad51, showed remarkable upregulation in cancer cells exposed to combination of drug-radiation treatment. The tumor burden was also relieved in xenograft mouse models with combination of drug-radiation treatment, indicating the potential of niraparib tosylate use clinical cancer therapy. Conclusion: From the results, a novel function of niraparib tosylate can be established, impairing DNA damage repair efficiency to increase the susceptibility of ESCC to radiotherapy, resulting in cell apoptosis and G2/M cycle arrest in vitro and in vivo.

DNA damage-induced EMT controlled by the PARP-dependent chromatin remodeler ALC1 promotes DNA repair efficiency through RAD51 in tumor cells.

Epithelial-to-mesenchymal transition (EMT) allows cancer cells to metastasize while acquiring resistance to apoptosis and chemotherapeutic agents with significant implications for patients' prognosis and survival. Despite its clinical relevance, the mechanisms initiating EMT during cancer progression remain poorly understood. We demonstrate that DNA damage triggers EMT and that activation of poly (ADP-ribose) polymerase (PARP) and the PARP-dependent chromatin remodeler ALC1 (CHD1L) was required for this response. Our results suggest that this activation directly facilitates access to the chromatin of EMT transcriptional factors (TFs) which then initiate cell reprogramming. We also show that EMT-TFs bind to the RAD51 promoter to stimulate its expression and to promote DNA repair by homologous recombination. Importantly, a clinically relevant PARP inhibitor reversed or prevented EMT in response to DNA damage while resensitizing tumor cells to other genotoxic agents. Overall, our observations shed light on the intricate relationship between EMT, DNA damage response, and PARP inhibitors, providing potential insights for in cancer therapeutics.

DNA repair and anti-cancer mechanisms in the long-lived bowhead whale.

At over 200 years, the maximum lifespan of the bowhead whale exceeds that of all other mammals. The bowhead is also the second-largest animal on Earth, reaching over 80,000 kg 1 . Despite its very large number of cells and long lifespan, the bowhead is not highly cancer-prone, an incongruity termed Peto's Paradox 2 . This phenomenon has been explained by the evolution of additional tumor suppressor genes in other larger animals, supported by research on elephants demonstrating expansion of the p53 gene 3-5 . Here we show that bowhead whale fibroblasts undergo oncogenic transformation after disruption of fewer tumor suppressors than required for human fibroblasts. However, analysis of DNA repair revealed that bowhead cells repair double strand breaks (DSBs) and mismatches with uniquely high efficiency and accuracy compared to other mammals. The protein CIRBP, implicated in protection from genotoxic stress, was present in very high abundance in the bowhead whale relative to other mammals. We show that CIRBP and its downstream protein RPA2, also present at high levels in bowhead cells, increase the efficiency and fidelity of DNA repair in human cells. These results indicate that rather than possessing additional tumor suppressor genes as barriers to oncogenesis, the bowhead whale relies on more accurate and efficient DNA repair to preserve genome integrity. This strategy which does not eliminate damaged cells but repairs them may be critical for the long and cancer-free lifespan of the bowhead whale.

RPS15 Coordinates with CtIP to Facilitate Homologous Recombination and Confer Therapeutic Resistance in Breast Cancer.

The repair of DNA double-strand breaks (DSBs) through homologous recombination (HR) is vital for maintaining the stability and integrity of the genome. RNA binding proteins (RBPs) intricately regulate the DNA damage repair process, yet the precise molecular mechanisms underlying their function remain incompletely understood. In this study, we highlight the pivotal role of RPS15, a representative RBP, in homologous recombination repair. Specifically, we demonstrate that RPS15 promotes DNA end resection, a crucial step in homologous recombination. Notably, we identify an interaction between RPS15 and CtIP, a key factor in homologous recombination repair. This interaction is essential for CtIP recruitment to DSB sites, subsequent RPA coating, and RAD51 replacement, all critical steps in efficient homologous recombination repair and conferring resistance to genotoxic treatments. Functionally, suppressing RPS15 expression sensitizes cancer cells to X-ray radiation and enhances the therapeutic synergistic effect of PARP1 inhibitors in breast cancer cells. In summary, our findings reveal that RPS15 promotes DNA end resection to ensure effective homologous recombination repair, suggesting its potential as a therapeutic target in cancer treatment.

Tenascin-C from the tissue microenvironment promotes muscle stem cell self-renewal through Annexin A2.

Skeletal muscle tissue self-repair occurs through the finely timed activation of resident muscle stem cells (MuSC). Following perturbation, MuSC exit quiescence, undergo myogenic commitment, and differentiate to regenerate the injured muscle. This process is coordinated by signals present in the tissue microenvironment, however the precise mechanisms by which the microenvironment regulates MuSC activation are still poorly understood. Here, we identified Tenascin-C (TnC), an extracellular matrix (ECM) glycoprotein, as a key player in promoting of MuSC self-renewal and function. We show that fibro-adipogenic progenitors (FAPs) are the primary cellular source of TnC during muscle repair, and that MuSC sense TnC signaling through cell the surface receptor Annexin A2. We provide in vivo evidence that TnC is required for efficient muscle repair, as mice lacking TnC exhibit a regeneration phenotype of premature aging. We propose that the decline of TnC in physiological aging contributes to inefficient muscle regeneration in aged muscle. Taken together, our results highlight the pivotal role of TnC signaling during muscle repair in healthy and aging skeletal muscle.

Zwiększenie wydajności urządzeń do frezowania i oczyszczania odwiertów z resztek po frezowaniu poprzez zastosowanie kawitacji w strefie frezowania

Technological leadership on a global scale is closely linked to advancements in novel technologies and materials. Increasing the operating temperature of composite materials is a critical objective in the development of innovative materials and products derived from them. Advances in technology have demonstrated that extensive alloying, combined with optimal heat treatment and advanced material processing methods, enhances their heat resistance. High-temperature materials based on composites with an elevated temperature threshold fulfill this requirement. In the current stage of oil and gas industry development, methods to increase oil and gas production include the introduction of effective technological processes aimed at enhancing oil recovery, maintaining production wells, and implementing preventive measures. Particularly important are efforts to accelerate emergency maintenance of production and drilling wells. In this context, the introduction of new, highly efficient repair equipment designs and the improvement of existing tools and devices used in the field play a crucial role. The primary well maintenance activities include fishing and milling. Tools and devices used in these operations are classified into gripping, cutting, and auxiliary categories. One of the most versatile tools in well repair are cutting devices, designed for continuous milling of pipes, preparing the deformed ends of emergency pipes for fishing, opening casings, and cutting out drilling columns. Restoring damaged wells by milling is one of the most complex types of repairs. The productivity of wellbore milling is characterized by the life of the tool, the rate of metal penetration, and durability.

Harnessing hydrogen sulfide in injectable hydrogels that guide the immune response and osteoclastogenesis balance for osteoporosis treatment

Elevated levels of oxidative stress, inflammation, and a dysregulated osteoclastogenesis balance frequently characterize the microenvironment of osteoporosis, which impedes the processes of healing and repair. Existing treatment approaches are limited in scope and rely primarily on factors and drugs. An injectable hydrogel designed for the ROS-responsive release of H2S gas is presented in this study. The first network of the hydrogel comprises sodium alginate (SA-SATO) chelated with S-aroylthiooxime (SATO) and an H2S-generating group, while the second network is composed of photocrosslinkable PEGDA. Through the integration of Cys-releasing microspheres that are reactive with ROS, a composite hydrogel was developed that exhibited advantageous mechanical characteristics and biosafety. The composite hydrogel effectively promoted osteogenic differentiation of mesenchymal stem cells, modulated macrophage polarization, decreased inflammatory responses, and halted cell apoptosis, as evidenced by in vitro experiments. Additionally, it released H2S gas and mitigated excess ROS in cells. The efficacy of the composite hydrogel in promoting bone defect repair and regeneration in an osteoporotic model was further validated by in vivo findings. In summary, the composite hydrogel exhibits potential as a viable approach to address osteoporotic bone defects by harmonizing osteogenesis and osteoclast activity, modulating the microenvironment of bone injuries, and reducing inflammation. Consequently, it presents a viable strategy for the efficient repair of bone defects.

Two-stage algorithm for automatic repair of pavement cracks

PurposeTo develop an automated system for identifying and repairing cracks in asphalt pavements, addressing the urgent need for efficient pavement maintenance solutions amidst increasing workloads and decreasing budgets.Design/methodology/approachThe research was conducted in two main stages: Crack identification: Utilizing the U-Net deep learning model for pixel-level segmentation to identify pavement cracks, followed by morphological operations such as thinning and spur removal to refine the crack trajectories. Automated crack repair path planning: Developing an enhanced hybrid ant colony greedy algorithm (EAC-GA), which integrates the ant colony (AC) algorithm, greedy algorithm (GA) and three local enhancement strategies – PointsExchange, Cracks2OPT and Nearby Cracks 2OPT – to plan the most efficient repair paths with minimal redundant distance.FindingsThe EAC-GA demonstrated significant advantages in solution quality compared to the GA, the traditional AC and the AC-GA. Experimental validation on repair areas with varying numbers of cracks (16, 26 and 36) confirmed the effectiveness and scalability of the proposed method.Originality/valueThe originality of this research lies in the application of advanced deep learning and optimization algorithms to the specific problem of pavement crack repair. The value is twofold: Technological innovation in the field of pavement maintenance, offering a more efficient and automated approach to a common and costly issue. The potential for significant economic and operational benefits, particularly in the context of reduced maintenance budgets and increasing maintenance demands.

Tough and anisotropic Janus hydrogel for tendon injury repair with controlled release of bFGF in tendon microenvironment

To address the high complexity and challenging nature of large-scale tendon injury repair, an innovative Janus structured hydrogel patch (JAHP@bFGF) was designed in this study. The patch combines microenvironmental responsiveness with efficient repair function, aiming to optimise and accelerate the tendon healing process. The outer layer is a PVA/SA/Na3Cit hydrogel with excellent mechanical properties, protein resistance, and low friction, which provides firm support to the tendon and reduces adhesions to ensure the recovery of gliding function. The inner layer of TCSB@bFGF microgel responds intelligently to changes in the microenvironment, precisely regulates the release of bFGF, promotes cell proliferation and migration, accelerates tissue regeneration, and has high adhesion strength and antimicrobial properties, which significantly reduces the risk of postoperative infection. Experimental results show that JAHP@bFGF significantly optimises the healing process, accelerates the repair speed and improves the repair quality under simulated large-scale tendon injury conditions. The unique Janus surface design and the intelligent drug release function, in synergy, not only bring new hope to patients with large-scale tendon injuries, but also provide an important reference for the application of biomedical materials in the repair of complex tissues, which heralds the arrival of the era of more efficient and personalised tendon repair.

Prediction of Power Equipment Emergency Repair Based on Adaptive Neural Network Fuzzy Inference Method

If the emergency repair prediction of power equipment is only made from the perspective of historical spare parts inventory data, it cannot reflect the impact of disaster-causing elements and disaster evolution on the demand for emergency repair spare parts in the future. Therefore, this paper aims to propose a reliable power equipment emergency repair prediction method, and constructs a demand prediction method for emergency repair spare parts of power equipment based on scenario analysis. Constructing a power equipment repair system through intelligent reasoning methods to improve the efficiency of power equipment repair. This article comprehensively uses methods such as literature analysis, model inference, and case simulation verification, this paper innovatively combines the adaptive neural network fuzzy inference system with expert experience. This paper validates the superiority of the prediction method constructed in this paper through comparative analysis. The results show that with the increase of the amount of data, the prediction accuracy of the method proposed in this paper will be improved, which can provide a reference for the subsequent emergency repair prediction of power equipment.

Evaluation and maintenance method for general speed railway turnouts based on multi-source data

In recent years, with the increasing passengers' requirements for safety and comfort, as well as the measures of increasing revenue and reducing the expenditure of railway company, more efficient, more scientific and more comprehensive requirements have been put forward for the maintenance of railway turnouts. This paper develops a maintenance strategy based on the Turnout Service State Indicator (TSSI), derived from an analysis of multi-source data concerning turnout conditions. The weights of critical indicators affecting turnout conditions are determined using Analytical Target Cascading (ATC) and Analytic Hierarchy Process (AHP). Subsequently, turnouts are classified into four categories—great, good, general, and poor—based on their TSSI values, guiding specific maintenance strategies. The proposed assessment method was validated using data from four sets of turnouts collected on actual tracks, showing consistency between the assessment results and field technicians' evaluations. A comparative analysis of the ATC and AHP suggests that the latter provides a more scientific and objective assessment of turnout conditions. The established methods for evaluating the service state and deciding on turnout maintenance actions have been proven feasible and practical through field validation. These methods can be broadly applied to maintain general speed railway turnouts to enhance repair efficiency and reduce maintenance costs.

Tetrameric INTS6-SOSS1 complex facilitates DNA:RNA hybrid autoregulation at double-strand breaks.

DNA double-strand breaks (DSBs) represent a lethal form of DNA damage that can trigger cell death or initiate oncogenesis. The activity of RNA polymerase II (RNAPII) at the break site is required for efficient DSB repair. However, the regulatory mechanisms governing the transcription cycle at DSBs are not well understood. Here, we show that Integrator complex subunit 6 (INTS6) associates with the heterotrimeric sensor of ssDNA (SOSS1) complex (comprising INTS3, INIP and hSSB1) to form the tetrameric SOSS1 complex. INTS6 binds to DNA:RNA hybrids and promotes Protein Phosphatase 2A (PP2A) recruitment to DSBs, facilitating the dephosphorylation of RNAPII. Furthermore, INTS6 prevents the accumulation of damage-associated RNA transcripts (DARTs)and the stabilization of DNA:RNA hybrids at DSB sites. INTS6 interacts with and promotes the recruitment of senataxin(SETX) to DSBs, facilitating the resolution of DNA:RNA hybrids/R-loops. Our results underscore the significance of the tetrameric SOSS1 complex in the autoregulation of DNA:RNA hybrids andefficient DNA repair.