Regulates DNA Damage Research Articles

DNAR-12. STEAROYL-COA DESATURASE REGULATES DNA DAMAGE REPAIR IN GBM BY MODULATING PARP1 ACTIVITY

Abstract Glioblastoma (GBM) is the most prevalent malignant brain cancer in adults, notorious for its aggressiveness and resistance to therapy. GBM patients commonly receive radiation therapy combined with temozolomide (TMZ), which engages tumor cells to promote lethal DNA damage and subsequent cytotoxicity. Active DNA repair mechanisms, particularly in a subset population of GBM stem-like cells (GSCs), drive therapeutic resistance, thus largely contributing to the bleak prognosis of GBM. Poly (ADP-ribose) polymerases (PARPs) are essential in various cellular processes, including DNA repair. We have previously reported that fatty acid desaturation mediated by Stearoyl-CoA desaturase 1 (SCD1) plays a cytoprotective role in GSCs. Inhibiting SCD prevents tumor initiation and inhibits DNA damage repair, hence sensitizing to radiation and TMZ. Yet, the mechanistic role of SCD in DNA damage regulation remained unknown. Here, we found that the expression of both human isoforms of SCD, SCD1, and SCD5, directly correlates with PARP protein levels and subcellular localization. Downregulating SCD1/5 in GSCs resulted in significantly lower levels of PARP1, coupled with increased DNA damage, as well as reduced DNA damage repair and chromosome assembly. Conversely, cells overexpressing SCD1/5 exhibited higher PARP1 expression and lower levels of basal DNA damage compared to control GSCs. Notably, SCD1/5 overexpression also led to increased resistance to TMZ. We show that SCD1/5 regulates PARP activity by controlling PARP1 subcellular localization. In addition to decreased total levels of PARP following SCD1/5 downregulation, we also found increased PARP1 self-PARylation. Using confocal microscopy, we show that when SCD1/5 is repressed, PARylated PARP translocates from the nucleus to the cytosol, rendering it unable to bind DNA and recruit DNA-repairing machinery. In conclusion, our study provides a direct link between fatty acid metabolism and PARP1-mediated DNA damage repair.

USP15 regulates radiation-induced DNA damage and intestinal injury through K48-linked deubiquitination and stabilisation of ATM

BackgroundRadiation-induced intestinal injury (RIII) interrupts the scheduled processes of abdominal and pelvic radiotherapy (RT) and compromises the quality of life of cancer survivors. However, the specific regulators and mechanisms underlying the effects of RIII remain unknown. The biological effects of RT are caused primarily by DNA damage, and ataxia telangiectasia mutated (ATM) is a core protein of the DNA damage response (DDR). However, whether ATM is regulated by deubiquitination signaling remains unclear.MethodsWe established animal and cellular models of RIII. The effects of ubiquitin-specific protease 15 (USP15) on DNA damage and radion-induced intestinal injury were evaluated. Mass spectrometry analysis, truncation tests, and immunoprecipitation were used to identify USP15 as a binding partner of ATM and to investigate the ubiquitination of ATM. Finally, the relationship between the USP15/ATM axes was further determined via subsequent experiments.ResultsIn this study, we identified the deubiquitylating enzyme USP15 as a regulator of DNA damage and the pathological progression of RIII. Irradiation upregulates the expression of USP15, whereas pharmacological inhibition of USP15 exacerbates radiation-induced DNA damage and RIII both in vivo and in vitro. Mechanistically, USP15 interacts with, deubiquitinates, and stabilises ATM via K48-linked deubiquitination. Notably, ATM overexpression blocks the effect of USP15 genetic inhibition on DNA damage and RIII progression.ConclusionsThese findings describe ATM as a novel deubiquitination target of USP15 upon radiation-induced DNA damage and intestinal injury, and provides experimental support for USP15/ATM axis as a potential target for developing strategies that mitigate RIII.

MiR-195-5p inhibits cisplatin resistance in lung adenocarcinoma by regulating DNA damage via targeting E2F7.

Lung adenocarcinoma (LUAD) emerges as one of the most lethal malignant tumors worldwide. Platinum-based combination chemotherapy remains one of the main methods for patients with advanced LUAD. Due to the resistance, the effect of this chemotherapy was not satisfactory. Therefore, studying the mechanism of cisplatin (DDP) resistance is essential for promoting the effect of this therapeutic strategy. Therefore, this work sought to probe the impact of E2F Transcription Factor 7 (E2F7) on LUAD resistance and the molecular regulatory mechanism. The mRNA expression level of the target gene E2F7 in LUAD was predicted by bioinformatics analysis, and regulatory miRNA upstream of the target gene was identified. The mRNA and protein expression of E2F7 in LUAD cells was detected through quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and Western blot, respectively. The expression of miR-195-5p in LUAD cells was measured via qRT-PCR. E2F7 high and low expression groups underwent enrichment analysis by utilizing Gene Set Enrichment Analysis software. The targeting relationship of miR-195-5p and E2F7 was validated by conducting a dual-luciferase reporter assay. The cell viability was tested through cell counting kit-8. The cell cycle was examined by flow cytometry. DNA damage level was determined via Comet assay and Western blot assay. The findings indicated that the mRNA and protein levels of E2F7 were high in LUAD. MiR-195-5p was the regulatory miRNA upstream of E2F7, and lowly expressed in LUAD. The cell experiments suggested that E2F7 advanced the DDP resistance of LUAD cells by repressing DNA damage. Finally, the rescue assay manifested that miR-195-5p overexpression could abate inhibition of E2F7 overexpression on the DNA damage and the DDP sensitivity of LUAD cells. MiR-195-5p raised the DDP sensitivity of LUAD cells by advancing the DNA damage in LUAD cells via inhibition of E2F7.

An integrative systems-biology approach defines mechanisms of Alzheimer's disease neurodegeneration.

Despite years of intense investigation, the mechanisms underlying neuronal death in Alzheimer's disease, the most common neurodegenerative disorder, remain incompletely understood. To define relevant pathways, we integrated the results of an unbiased, genome-scale forward genetic screen for age-associated neurodegeneration in Drosophila with human and Drosophila Alzheimer's disease-associated multi-omics. We measured proteomics, phosphoproteomics, and metabolomics in Drosophila models of Alzheimer's disease and identified Alzheimer's disease human genetic variants that modify expression in disease-vulnerable neurons. We used a network optimization approach to integrate these data with previously published Alzheimer's disease multi-omic data. We computationally predicted and experimentally demonstrated how HNRNPA2B1 and MEPCE enhance tau-mediated neurotoxicity. Furthermore, we demonstrated that the screen hits CSNK2A1 and NOTCH1 regulate DNA damage in Drosophila and human iPSC-derived neural progenitor cells. Our work identifies candidate pathways that could be targeted to ameliorate neurodegeneration in Alzheimer's disease.

Yeast Nat4 regulates DNA damage checkpoint signaling through its N-terminal acetyltransferase activity on histone H4.

The DNA damage response (DDR) constitutes a vital cellular process that safeguards genome integrity. This biological process involves substantial alterations in chromatin structure, commonly orchestrated by epigenetic enzymes. Here, we show that the epigenetic modifier N-terminal acetyltransferase 4 (Nat4), known to acetylate the alpha-amino group of serine 1 on histones H4 and H2A, is implicated in the response to DNA damage in S. cerevisiae. Initially, we demonstrate that yeast cells lacking Nat4 have an increased sensitivity to DNA damage and accumulate more DNA breaks than wild-type cells. Accordingly, upon DNA damage, NAT4 gene expression is elevated, and the enzyme is specifically recruited at double-strand breaks. Delving deeper into its effects on the DNA damage signaling cascade, nat4-deleted cells exhibit lower levels of the damage-induced modification H2AS129ph (γH2A), accompanied by diminished binding of the checkpoint control protein Rad9 surrounding the double-strand break. Consistently, Mec1 kinase recruitment at double-strand breaks, critical for H2AS129ph deposition and Rad9 retention, is significantly impaired in nat4Δ cells. Consequently, Mec1-dependent phosphorylation of downstream effector kinase Rad53, indicative of DNA damage checkpoint activation, is reduced. Importantly, we found that the effects of Nat4 in regulating the checkpoint signaling cascade are mediated by its N-terminal acetyltransferase activity targeted specifically towards histone H4. Overall, this study points towards a novel functional link between histone N-terminal acetyltransferase Nat4 and the DDR, associating a new histone-modifying activity in the maintenance of genome integrity.

The Role of Natural Background Radiation in Maintaining Genomic Stability in the CGL1 Human Hybrid Model System.

Natural background ionizing radiation is present on the earth's surface; however, the biological role of this chronic low-dose-rate exposure remains unknown. The Researching the Effects of the Presence and Absence of Ionizing Radiation (REPAIR) project is examining the impacts of sub-natural background radiation exposure through experiments conducted 2 km underground in SNOLAB. The rock overburden combined with experiment-specific shielding provides a background radiation dose rate 30 times lower than on the surface. We hypothesize that natural background radiation is essential for life and maintains genomic stability and that prolonged exposure to sub-background environments will be detrimental to biological systems. To evaluate this, human hybrid CGL1 cells were continuously cultured in SNOLAB and our surface control laboratory for 16 weeks. Cells were assayed every 4 weeks for growth rate, alkaline phosphatase (ALP) activity (a marker of cellular transformation in the CGL1 system), and the expression of genes related to DNA damage and cell cycle regulation. A subset of cells was also exposed to a challenge radiation dose (0.1 to 8 Gy of X rays) and assayed for clonogenic survival and DNA double-strand break induction to examine if prolonged sub-background exposure alters the cellular response to high-dose irradiation. At each 4-week time point, sub-background radiation exposure did not significantly alter cell growth rates, survival, DNA damage, or gene expression. However, cells cultured in SNOLAB showed significantly higher ALP activity, a marker of carcinogenesis in these cells, which increased with longer exposure to the sub-background environment, indicative of neoplastic progression. Overall, these data suggest that sub-background radiation exposure does not impact growth, survival, or DNA damage in CGL1 cells but may lead to increased rates of neoplastic transformation, highlighting a potentially important role for natural background radiation in maintaining normal cellular function and genomic stability.

Regulation of yeast <i>RAD9</i> gene in energy charge, intracellular ROS, and cell cycle arrest in response to DNA damage

In various environmental conditions, eukaryotic cells are exposed to many kinds of exogenous toxic agents as well as to endogenous agents like reactive oxygen species (ROS) generated from oxidative metabolism that can all result in damage to DNA. To cope with these types of damage, yeast cells have evolved a number of mechanisms and specific response systems regulated by key control genes. One of which is RAD9 gene that regulates DNA damage and repair checkpoints, and cell cycle arrest. Thus, a series of methods, e.g. oxygen consumption monitoring, physicochemical analysis, and flow cytometry, were used in the present study to investigate the role of the RAD9 gene by using the BY4742 (wild type) and specific knock-out yeast strains (∆rad9) and elucidate the function of this gene in cellular defense mechanism and metabolic response to DNA damage triggered by methyl methanesulfonate (MMS) treatment. The results indicated that fully functional DNA damage repair and cell cycle checkpoint (RAD9, wild type) significantly enhanced mitochondrial activity and oxygen consumption, reduced intracellular ROS accumulation. Fully functional mitochondria attenuated ROS accumulation, enabled efficient mitochondrial electron transport chain (mtETC) and ATP synthesis, and stabilized cellular energy status. Also, high mitochondrial activity acted as a protective mechanism against oxidative stress. In contrast, deletion of the RAD9 (∆rad9) resulted in high ROS accumulation and damaged to mitochondrial DNA, leading to strong inhibition of mitochondrial activity and oxygen consumption. Furthermore, low mitochondrial activity in cells lacking RAD9 (∆rad9) led to the development of oxidative stress. Subsequently, high ROS accumulation in ∆rad9 cells caused a block of the mtETC, repression of ATP synthesis, fluctuation of cellular energy status, and induction of cell cycle arrest at S and G2/M phases.

The Impact of Lifestyle and Environmental Factors on Cancer Risk and Prevention

Cancer remains a leading cause of mortality globally, with a multifaceted etiology involving genetic, lifestyle, and environmental factors. This review article examines the impact of lifestyle and environmental factors on cancer risk and prevention, focusing on dietary habits, physical activity, tobacco use, alcohol consumption, and environmental exposures such as pollution, occupational hazards, and radiation. Lifestyle factors such as a balanced diet, regular exercise, and smoking cessation are shown to significantly influence cancer risk, while environmental factors like pollution and radiation exposure also play critical roles in cancer development. The review details the mechanisms through which these factors contribute to cancer, including DNA damage, inflammation, and hormonal regulation. Public health initiatives, policy regulations, and screening strategies are discussed as essential components of effective cancer prevention. Methodologically, this review synthesizes recent research findings and current evidence to provide a comprehensive overview of how lifestyle and environmental modifications can be leveraged to reduce cancer risk. Through this analysis, the article aims to offer valuable insights into enhancing cancer prevention strategies and improving public health outcomes. Keywords: Cancer Prevention, Lifestyle Factors, Environmental Exposure, Public Health, Risk Reduction

MANCR lncRNA Modulates Cell-Cycle Progression and Metastasis by Cis-Regulation of Nuclear Rho-GEF.

A significant number of the genetic alterations observed in cancer patients lie within nonprotein-coding segments of the genome, including regions coding for long noncoding RNAs (lncRNAs). LncRNAs display aberrant expression in breast cancer (BrCa), but the functional implications of this altered expression remain to be elucidated. By performing transcriptome screen in a triple negative BrCa (TNBC) isogenic 2D and 3D spheroid model, we observed aberrant expression of >1000 lncRNAs during BrCa progression. The chromatin-associated lncRNA MANCR shows elevated expression in metastatic TNBC. MANCR is upregulated in response to cellular stress and modulates DNA repair and cell proliferation. MANCR promotes metastasis as MANCR-depleted cells show reduced cell migration, invasion, and wound healing invitro, and reduced metastatic lung colonization in xenograft experiments invivo. Transcriptome analyses reveal that MANCR modulates expression and pre-mRNA splicing of genes, controlling DNA repair and checkpoint response. MANCR promotes the transcription of NET1A, a Rho-GEF that regulates DNA damage checkpoint and metastatic processes in cis, by differential promoter usage. Experiments suggest that MANCR regulates the expression of cancer-associated genes by modulating the association of various transcription factors and RNA-binding proteins. Our results identified the metastasis-promoting activities of MANCR in TNBC by cis-regulation of gene expression.

Abstract We019: YAP Overcomes Mechanical Barriers to Induce Adult Cardiomyocyte Division

Adult mammalian cardiomyocytes (CMs) are among the least able to renew of all cell types. CMs exit the cell cycle soon after birth and remain cell cycle arrested by unknown mechanisms. We previously found that in adult CMs, the active form of the Hippo signaling pathway effector YAP, YAP5SA, induces cell division in vivo . Here, we analyze the mechanism by which YAP5SA regulates the cell cycle in adult CMs. YAP5SA-expressing adult CMs reenter the cell cycle at the G1/S transition and have a prolonged S-phase lasting approximately 48 hours. Molecular and functional analysis revealed that progression from S to G2 phase, and the induction of mitotic rounding, requires sarcomere disassembly. Transition from G2 to M phase requires overcoming DNA damage checkpoint facilitated by the activation of the P21 degradation pathway. Clonal analysis showed that approximately 20% of CMs progress through cytokinesis. Our results show that multiple barriers are involved in suppressing the adult CM cell cycle. These include the structural block caused by the highly structured CM cytoskeleton and the P21 regulated DNA damage checkpoint.

The impact of SOX4-activated CTHRC1 transcriptional activity regulating DNA damage repair on cisplatin resistance in lung adenocarcinoma.

Lung adenocarcinoma (LUAD) is the predominant subtype within the spectrum of lung malignancies. CTHRC1 has a pro-oncogenic role in various cancers. Here, we observed the upregulation of CTHRC1 in LUAD, but its role in cisplatin resistance in LUAD remains unclear. Bioinformatics analysis was employed to detect CTHRC1 and SRY-related HMG-box 4 (SOX4) expression in LUAD. Gene Set Enrichment Analysis predicted the enriched pathways related to CTHRC1. JASPAR and MotifMap databases predicted upstream transcription factors of CTHRC1. Pearson analysis was conducted to analyze the correlation between genes of interest. The interaction and binding relationship between CTHRC1 and SOX4 were validated through dual-luciferase and chromatin immunoprecipitation assays. Quantitative real-time polymerase chain reaction determined the expression of CTHRC1 and SOX4 genes. CCK-8 was performed to assess cell viability and calculate IC50 value. Flow cytometry examined the cell cycle. Comet assay and western blot assessed DNA damage. CTHRC1 and SOX4 were upregulated in LUAD. CTHRC1 exhibited higher expression in cisplatin-resistant A549 cells compared to cisplatin-sensitive A549 cells. Knockdown of CTHRC1 enhanced DNA damage during cisplatin treatment and increased the sensitivity of LUAD cells to cisplatin. Additionally, SOX4 modulated DNA damage repair (DDR) by activating CTHRC1 transcriptional activity, promoting cisplatin resistance in LUAD cells. SOX4 regulated DDR by activating CTHRC1, thereby enhancing cisplatin resistance in LUAD cells. The finding provides a novel approach to address clinical cisplatin resistance in LUAD, with CTHRC1 possibly serving as a candidate for targeted therapies in addressing cisplatin resistance within LUAD.

191 USP15 regulates DNA damage repair by modulating ATM stability in intestinal epithelial cells

191 USP15 regulates DNA damage repair by modulating ATM stability in intestinal epithelial cells

192 p53 oscillatory activation regulates DNA damage repair in intestinal stem cells after radiation

192 p53 oscillatory activation regulates DNA damage repair in intestinal stem cells after radiation

How does orthodontic tooth movement influence the dental pulp? RNA-sequencing on human premolars.

The objective of this study is to analyse the gene expression profile of the dental pulp (DP) of human premolars subjected to 7 and 28 days of orthodontic force (OF) in vivo by using RNA sequencing. The maxillary and mandibular DP were additionally compared. Healthy patients requiring orthodontic premolar extractions were randomly assigned to one of the three groups: control (CG) where no OF was applied, 7 and 28 days, where premolars were extracted either 7 or 28 days after the application of a 50-100 g OF. Total RNA was extracted from the DP and analysed via RNA-seq. Differentially expressed genes (DEGs) were identified using a false discovery rate and fold change threshold of <0.05 and ≥1.5, respectively. Functional analysis was performed. After 7 days of OF, pulp reaction indicates immune response, hypoxia, DNA damage and epigenetic regulation. After 28 days, cell adhesion, migration, organization and tissue repair are evident. The maxillary and mandibular pulp tissues react differently to OF. The maxilla exhibits minimal alterations, mostly related to immune response at 7 days and tissue repair at 28 days, whereas the mandible shows mostly DNA damage and epigenetic regulation at 7 days and return to the original state at 28 days. This study demonstrates that the early reaction of the DP to OF is marked by immune response, hypoxia and DNA damage. In contrast, after 28 days, cell adhesion, migration, organization, tissue repair and dentine formation are observed. Maxillary and mandibular premolars react differently to OF: although the maxilla exhibits minimal alterations at both time points, the mandible mostly shows DNA damage, epigenetic regulation, and immune response at 7 days. These disparities could stem from different blood supplies or the lower maxillary bone density, potentially triggering faster biological changes. Our findings provide insights into the gene regulatory networks modulating DP response to OF.

Nano-enabled regulation of DNA damage in tumor cells to enhance neoantigen-based pancreatic cancer immunotherapy

Low-expression antigens, especially neoantigens, pose a significant challenge in immunotherapy for low immunogenicity pancreatic cancer. Increasing the tumor mutation burden is crucial to enhance the expression of tumor antigens and improve tumor immunogenicity. However, the incomplete intervention in DNA stability hampers effective elevation of the tumor mutation burden, thus reducing the probability of neoantigen. To address this issue, we have developed a novel nano-regulator that intervenes in the DNA stability of tumor cells, thereby enhancing tumor mutations. This nano-regulator comprises metal-organic frameworks (MOFs) encapsulating DNA damage agent doxorubicin and DNA damage repair inhibitor siRNA-ATR, enabling simultaneous induction of DNA mutations and inhibition of their repair. Importantly, this regulator, named as MOFDOX&siATR, can modulate the tumor gene expression profile, induce the production of neoantigens of Atp8b1, and enhance the immunogenicity of pancreatic cancer. The characteristics of DNA stability intervention by MOFDOX&siATR hold promise for augmenting the immune response in low immunogenic tumors, making it a potential nanomedicine for the treatment of pancreatic cancer.

CircPCMTD1 : A protein-coding circular RNA that regulates DNA damage response in BCR/ABL -positive leukemias.

Circular RNAs are a novel class of RNA transcripts, which regulate important cellular functions in health and disease. Herein, we report on the functional relevance of the circPCMTD1 transcript in acute leukemias. In screening experiments, we found that circPCMTD1 depletion strongly inhibited the proliferative capacity of leukemic cells with BCR-ABL translocations. Mass cytometry experiments identified the aberrant activation of the DNA damage response as an early downstream event of circPCMTD1 depletion. In in vivo experiments, circPCMTD1 targeting prolonged the survival of mice engrafted with leukemic blasts harboring the Philadelphia chromosome. Mechanistically, we found that circPCMTD1 was enriched in the cytoplasm and associated with the ribosomes of the leukemic cells. We detected a cryptic open reading frame within the circPCMTD1 sequence and found that circPCMTD1 could generate a peptide product. The circPCMTD 1-derived peptide interacted with proteins of the BTR complex and enhanced BTR complex formation, thereby increasing tolerance to genotoxic stress.

YTHDC1 m6A-dependent and m6A-independent functions converge to preserve the DNA damage response

Cells have evolved a robust and highly regulated DNA damage response to preserve their genomic integrity. Although increasing evidence highlights the relevance of RNA regulation, our understanding of its impact on a fully efficient DNA damage response remains limited. Here, through a targeted CRISPR-knockout screen, we identify RNA-binding proteins and modifiers that participate in the p53 response. Among the top hits, we find the m6A reader YTHDC1 as a master regulator of p53 expression. YTHDC1 binds to the transcription start sites of TP53 and other genes involved in the DNA damage response, promoting their transcriptional elongation. YTHDC1 deficiency also causes the retention of introns and therefore aberrant protein production of key DNA damage factors. While YTHDC1-mediated intron retention requires m6A, TP53 transcriptional pause-release is promoted by YTHDC1 independently of m6A. Depletion of YTHDC1 causes genomic instability and aberrant cancer cell proliferation mediated by genes regulated by YTHDC1. Our results uncover YTHDC1 as an orchestrator of the DNA damage response through distinct mechanisms of co-transcriptional mRNA regulation.

5-aminolevulinic acid photodynamic therapy protects against UVB-induced skin photoaging: A DNA-repairing mechanism involving the BER signalling pathway.

Low-dose 5-aminolevulinic acid photodynamic therapy (ALA-PDT) has been used to cope with skin photoaging, and is thought to involve DNA damage repair responses. However, it is still unknown how low-dose ALA-PDT regulates DNA damage repair to curb skin photoaging. We established a photoaging model using human dermal fibroblasts (HDFs) and rat skin. RNA-sequencing (RNA-seq) analysis was conducted to identify differentially expressed genes (DEGs) in HDFs before and after low-dose ALA-PDT treatment, followed by bioinformatics analysis. Senescence-associated β-galactosidase (SA-β-gal) staining was employed to assess skin aging-related manifestations and Western blotting to evaluate the expression of associated proteins. A comet assay was used to detect cellular DNA damage, while immunofluorescence to examine the expression of 8-hydroxy-2'-deoxyguanosine (8-oxo-dG) in cells and skin tissues. In both invivo and invitro models, low-dose ALA-PDT alleviated the manifestations of ultraviolet B (UVB)-induced skin photoaging. Low-dose ALA-PDT significantly reduced DNA damage in photoaged HDFs. Furthermore, low-dose ALA-PDT accelerated the clearance of the photoproduct 8-oxo-dG in photoaged HDFs and superficial dermis of photoaged rat skin. RNA-seq analysis suggested that low-dose ALA-PDT upregulated the expression of key genes in the base excision repair (BER) pathway. Further functional validation showed that inhibition on BER expression by using UPF1069 significantly suppressed SA-β-gal activity, G2/M phase ratio, expression of aging-associated proteins P16, P21, P53, and MUTYH proteins, as well as clearance of the photoproduct 8-oxo-dG in photoaged HDFs. Low-dose ALA-PDT exerts anti-photoaging effects by activating the BER signalling pathway.

Harmine inhibits pulmonary fibrosis through regulating DNA damage repair-related genes and activation of TP53-Gadd45α pathway

BackgroundHarmine has many pharmacological activities and has been found to significantly inhibit the fibrosis of keloid fibroblasts. DNA damage repair (DDR) is essential to prevent fibrosis. This study aimed to investigate the effects of harmine on pulmonary fibrosis and its underlying mechanisms. MethodsBleomycin and TGF-β1 were used to construct pulmonary fibrosis models in vivo and in vitro, then treated with harmine to explore harmine’s effects in treating experimental pulmonary fibrosis and its related mechanisms. Then, RNA sequencing was applied to investigate further the crucial DDR-related genes and drug targets of harmine against pulmonary fibrosis. Finally, the expression levels of DDR-related genes were verified by real-time quantitative PCR (RT-qPCR) and western blot. ResultsOur in vivo experiments showed that harmine treatment could improve weight loss and lung function and reduce tissue fibrosis in mice with pulmonary fibrosis. The results confirmed that harmine could inhibit the viability and migration of TGF-β1-induced MRC-5 cells, induce their apoptosis, and suppress the F-actin expression, suggesting that harmine could suppress the phenotypic transition from lung fibroblasts to lung myoblasts. In addition, RNA sequencing identified 1692 differential expressed genes (DEGs), and 10 DDR-related genes were screened as critical DDR-related genes. RT-qPCR and western blotting showed that harmine could down-regulate the expression of CHEK1, ERCC1, ERCC4, POLD1, RAD51, RPA1, TOP1, and TP53, while up-regulate FEN1, H2AX and GADD45α expression. ConclusionsHarmine may inhibit pulmonary fibrosis by regulating DDR-related genes and activating the TP53-Gadd45α pathway.

PARticular MARks: Histone ADP-ribosylation and the DNA damage response

Cellular and molecular responses to DNA damage are highly orchestrated and dynamic, acting to preserve the maintenance and integrity of the genome. Histone proteins bind DNA and organize the genome into chromatin. Post-translational modifications of histones have been shown to play an essential role in orchestrating the chromatin response to DNA damage by regulating the DNA damage response pathway. Among the histone modifications that contribute to this intricate network, histone ADP-ribosylation (ADPr) is emerging as a pivotal component of chromatin-based DNA damage response (DDR) pathways. In this review, we survey how histone ADPr is regulated to promote the DDR and how it impacts chromatin and other histone marks. Recent advancements have revealed histone ADPr effects on chromatin structure and the regulation of DNA repair factor recruitment to DNA lesions. Additionally, we highlight advancements in technology that have enabled the identification and functional validation of histone ADPr in cells and in response to DNA damage. Given the involvement of DNA damage and epigenetic regulation in human diseases including cancer, these findings have clinical implications for histone ADPr, which are also discussed. Overall, this review covers the involvement of histone ADPr in the DDR and highlights potential future investigations aimed at identifying mechanisms governed by histone ADPr that participate in the DDR, human diseases, and their treatments.