DNA damage response

Radio-miRs: a comprehensive view of radioresistance-related microRNAs

Radiotherapy is a key treatment option for a wide variety of human tumors, employed either alone or alongside with other therapeutic interventions. Radiotherapy uses high-energy particles to destroy tumor cells, blocking their ability to divide and proliferate. The effectiveness of radiotherapy is due to genetic and epigenetic factors that determine how tumor cells respond to ionizing radiation. These factors contribute to the establishment of resistance to radiotherapy, which increases the risk of poor clinical prognosis of patients. Although the mechanisms by which tumor cells induce radioresistance are unclear, evidence points out several contributing factors including the overexpression of DNA repair systems, increased levels of reactive oxygen species, alterations in the tumor microenvironment, and enrichment of cancer stem cell populations. In this context, dysregulation of microRNAs or miRNAs, critical regulators of gene expression, may influence how tumors respond to radiation. There is increasing evidence that miRNAs may act as sensitizers or enhancers of radioresistance, regulating key processes such as the DNA damage response and the cell death signaling pathway. Furthermore, expression and activity of miRNAs have shown informative value in overcoming radiotherapy and long-term radiotoxicity, revealing their potential as biomarkers. In this review, we will discuss the molecular mechanisms associated with the response to radiotherapy and highlight the central role of miRNAs in regulating the molecular mechanisms responsible for cellular radioresistance. We will also review radio-miRs, radiotherapy-related miRNAs, either as sensitizers or enhancers of radioresistance that hold promise as biomarkers or pharmacological targets to sensitize radioresistant cells.

Emerging paradigms: unmasking the role of oxidative stress in HPV-induced carcinogenesis

The contribution of the human papillomavirus (HPV) to cancer is significant but not exclusive, as carcinogenesis involves complex mechanisms, notably oxidative stress. Oxidative stress and HPV can independently cause genome instability and DNA damage, contributing to tumorigenesis. Oxidative stress-induced DNA damage, especially double-strand breaks, aids in the integration of HPV into the host genome and promotes the overexpression of two viral proteins, E6 and E7. Lifestyle factors, including diet, smoking, alcohol, and psychological stress, along with genetic and epigenetic modifications, and viral oncoproteins may influence oxidative stress, impacting the progression of HPV-related cancers. This review highlights various mechanisms in oxidative-induced HPV-mediated carcinogenesis, including altered mitochondrial morphology and function leading to elevated ROS levels, modulation of antioxidant enzymes like Superoxide Dismutase (SOD), Glutathione (GSH), and Glutathione Peroxidase (GPx), induction of chronic inflammatory environments, and activation of specific cell signaling pathways like the Phosphoinositide 3-kinase, Protein kinase B, Mammalian target of rapamycin (PI3K/AKT/mTOR) and the Extracellular signal-regulated kinase (ERK) signaling pathway. The study highlights the significance of comprehending and controlling oxidative stress in preventing and treating cancer. We suggested that incorporating dietary antioxidants and targeting cancer cells through mechanisms involving ROS could be potential interventions to mitigate the impact of oxidative stress on HPV-related malignancies.

Human Aging and Age-Related Diseases: From Underlying Mechanisms to Pro-Longevity Interventions

As human life expectancy continues to rise, becoming a pressing global concern, it brings into focus the underlying mechanisms of aging. The increasing lifespan has led to a growing elderly population grappling with age-related diseases (ARDs), which strains healthcare systems and economies worldwide. While human senescence was once regarded as an immutable and inexorable phenomenon, impervious to interventions, the emerging field of geroscience now offers innovative approaches to aging, holding the promise of extending the period of healthspan in humans. Understanding the intricate links between aging and pathologies is essential in addressing the challenges presented by aging populations. A substantial body of evidence indicates shared mechanisms and pathways contributing to the development and progression of various ARDs. Consequently, novel interventions targeting the intrinsic mechanisms of aging have the potential to delay the onset of diverse pathological conditions, thereby extending healthspan. In this narrative review, we discuss the most promising methods and interventions aimed at modulating aging, which harbor the potential to mitigate ARDs in the future. We also outline the complexity of senescence and review recent empirical evidence to identify rational strategies for promoting healthy aging.

DNA Damage Checkpoints Govern Global Gene Transcription and Exhibit Species-Specific Regulation on HOF1 in Candida albicans

DNA damage checkpoints are essential for coordinating cell cycle arrest and gene transcription during DNA damage response. Exploring the targets of checkpoint kinases in Saccharomyces cerevisiae and other fungi has expanded our comprehension of the downstream pathways involved in DNA damage response. While the function of checkpoint kinases, specifically Rad53, is well documented in the fungal pathogen Candida albicans, their targets remain poorly understood. In this study, we explored the impact of deleting RAD53 on the global transcription profiles and observed alterations in genes associated with ribosome biogenesis, DNA replication, and cell cycle. However, the deletion of RAD53 only affected a limited number of known DNA damage-responsive genes, including MRV6 and HMX1. Unlike S. cerevisiae, the downregulation of HOF1 transcription in C. albicans under the influence of Methyl Methanesulfonate (MMS) did not depend on Dun1 but still relied on Rad53 and Rad9. In addition, the transcription factor Mcm1 was identified as a regulator of HOF1 transcription, with evidence of dynamic binding to its promoter region; however, this dynamic binding was interrupted following the deletion of RAD53. Furthermore, Rad53 was observed to directly interact with the promoter region of HOF1, thus suggesting a potential role in governing its transcription. Overall, checkpoints regulate global gene transcription in C. albicans and show species-specific regulation on HOF1; these discoveries improve our understanding of the signaling pathway related to checkpoints in this pathogen.

The Influence of Oxidized Imino-Allantoin in the Presence of OXOG on Double Helix Charge Transfer: A Theoretical Approach

The genome is continuously exposed to a variety of harmful factors that result in a significant amount of DNA damage. This article examines the influence of a multi-damage site containing oxidized imino-allantoin (OXIa) and 7,8-dihydro-8-oxo-2'-deoxyguanosine (OXOdG) on the spatial geometry, electronic properties, and ds-DNA charge transfer. The ground stage of a d[A1OXIa2A3OXOG4A5]*d[T5C4T3C2T1] structure was obtained at the M06-2X/6-D95**//M06-2X/sto-3G level of theory in the condensed phase, with the energies obtained at the M06-2X/6-31++G** level. The non-equilibrated and equilibrated solvent-solute interactions were also considered. Theoretical studies reveal that the radical cation prefers to settle on the OXOG moiety, irrespective of the presence of OXIa in a ds-oligo. The lowest vertical and adiabatic ionization potential values were found for the OXOG:::C base pair (5.94 and 5.52 [eV], respectively). Conversely, the highest vertical and adiabatic electron affinity was assigned for OXIaC as follows: 3.15 and 3.49 [eV]. The charge transfers were analyzed according to Marcus' theory. The highest value of charge transfer rate constant for hole and excess electron migration was found for the process towards the OXOGC moiety. Surprisingly, the values obtained for the driving force and activation energy of electro-transfer towards OXIa2C4 located this process in the Marcus inverted region, which is thermodynamically unfavorable. Therefore, the presence of OXIa can slow down the recognition and removal processes of other DNA lesions. However, with regard to anticancer therapy (radio/chemo), the presence of OXIa in the structure of clustered DNA damage can result in improved cancer treatment outcomes.

A Prognostic Model for Prostate Cancer Patients Based on Two DNA Damage Response Mutation-Related Immune Genes

Background: DNA damage response (DDR) mutation-related genes and composition of immune cells are core factors affecting the effectiveness of immune checkpoint inhibitor therapy. The aim of this study is to combine DDR with immune-related genes to screen the prognostic signature for prostate cancer (PCa). Methods: Gene expression profile and somatic mutation were downloaded from The Cancer Genome Atlas (TCGA). DDR-related genes were obtained from published study. After identification of prognostic-related DDR genes, samples were divided into mutation and nonmutation groups. Differentially expressed genes between these two groups were screened, followed by selection of immune-related DDR genes. Univariate and multivariate Cox analyses were performed to screen genes for constructing prognostic model. Nomogram model was also developed. The expression level of signature was detected by quantitative real-time PCR (qPCR). Results: Two genes (MYBBP1A and PCDHA9) were screened to construct the prognostic model, and it showed good risk prediction of PCa prognosis. Survival analysis showed that patients in high-risk group had worse overall survival than those in low-risk group. Cox analyses indicated that risk score could be used as an independent prognostic factor for PCa. qPCR results indicated that MYBBP1A was upregulated, whereas PCDHA9 was downregulated in PCa cell lines. Conclusions: A prognostic model based on DDR mutation-related genes for PCa was established, which serves as an effective tool for prognostic differentiation in patients with PCa.

DNA-PK and ATM drive phosphorylation signatures that antagonistically regulate cytokine responses to herpesvirus infection or DNA damage

The DNA-dependent protein kinase, DNA-PK, is an essential regulator of DNA damage repair. DNA-PK-driven phosphorylation events and the activated DNA damage response (DDR) pathways are also components of antiviral intrinsic and innate immune responses. Yet, it is not clear whether and how the DNA-PK response differs between these two forms of nucleic acid stress-DNA damage and DNA virus infection. Here, we define DNA-PK substrates and the signature cellular phosphoproteome response to DNA damage or infection with the nuclear-replicating DNA herpesvirus, HSV-1. We establish that DNA-PK negatively regulates the ataxia-telangiectasia-mutated (ATM) DDR kinase during viral infection. In turn, ATM blocks the binding of DNA-PK and the nuclear DNA sensor IFI16 to viral DNA, thereby inhibiting cytokine responses. However, following DNA damage, DNA-PK enhances ATM activity, which is required for IFN-β expression. These findings demonstrate that the DDR autoregulates cytokine expression through the opposing modulation of DDR kinases.

Neuroglia targeting nano-therapeutic approaches to rescue aging and neurodegenerating brain

Despite intense efforts at the bench, the development of successful brain-targeting therapeutics to relieve malicious neural diseases remains primitive. The brain, being a beautifully intricate organ, consists of heterogeneous arrays of neuronal and glial cells. Primarily acting as the support system for neuronal functioning and maturation, glial cells have been observed to be engaged more apparently in the progression and worsening of various neural pathologies. The diseased state is often related to metabolic alterations in glial cells, thereby modulating their physiological homeostasis in conjunction with neuronal dysfunction. A plethora of data indicates the effect of oxidative stress, protein aggregation, and DNA damage in neuroglia impairments. Still, a deeper insight is needed to gain a conflict-free understanding in this arena. As a consequence, glial cells hold the potential to be identified as promising targets for novel therapeutic approaches aimed at brain protection. In this review, we describe the recent strides taken in the direction of understanding the impact of oxidative stress, protein aggregation, and DNA damage on neuroglia impairment and neuroglia-directed nanotherapeutic approaches to mitigate the burden of various neural disorders.

The role of Transcription Factor IIH complex in nucleotide excision repair

DNA damage occurs throughout life from a variety of sources, and it is imperative to repair damage in a timely manner to maintain genome stability. Thus, DNA repair mechanisms are a fundamental part of life. Nucleotide excision repair (NER) plays an important role in the removal of bulky DNA adducts, such as cyclobutane pyrimidine dimers from ultraviolet light or DNA crosslinking damage from platinum-based chemotherapeutics, such as cisplatin. A main component for the NER pathway is transcription factor IIH (TFIIH), a multifunctional, 10-subunit protein complex with crucial roles in both transcription and NER. In transcription, TFIIH is a component of the pre-initiation complex and is important for promoter opening and the phosphorylation of RNA Polymerase II (RNA Pol II). During repair, TFIIH is important for DNA unwinding, recruitment of downstream repair factors, and verification of the bulky lesion. Several different disease states can arise from mutations within subunits of the TFIIH complex. Most strikingly are xeroderma pigmentosum (XP), XP combined with Cockayne syndrome (CS), and trichothiodystrophy (TTD). Here, we summarize the recruitment and functions of TFIIH in the two NER subpathways, global genomic (GG-NER) and transcription-coupled NER (TC-NER). We will also discuss how TFIIH's roles in the two subpathways lead to different genetic disorders.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

The Link between Autosomal Dominant Polycystic Kidney Disease and Chromosomal Instability: Exploring the Relationship

In autosomal dominant polycystic kidney disease (ADPKD) with germline mutations in a PKD1 or PKD2 gene, innumerable cysts develop from tubules, and renal function deteriorates. Second-hit somatic mutations and renal tubular epithelial (RTE) cell death are crucial features of cyst initiation and disease progression. Here, we use established RTE lines and primary ADPKD cells with disease-associated PKD1 mutations to investigate genomic instability and DNA damage responses. We found that ADPKD cells suffer severe chromosome breakage, aneuploidy, heightened susceptibility to DNA damage, and delayed checkpoint activation. Immunohistochemical analyses of human kidneys corroborated observations in cultured cells. DNA damage sensors (ATM/ATR) were activated but did not localize at nuclear sites of damaged DNA and did not properly activate downstream transducers (CHK1/CHK2). ADPKD cells also had the ability to transform, as they achieved high saturation density and formed colonies in soft agar. Our studies indicate that defective DNA damage repair pathways and the somatic mutagenesis they cause contribute fundamentally to the pathogenesis of ADPKD. Acquired mutations may alternatively confer proliferative advantages to the clonally expanded cell populations or lead to apoptosis. Further understanding of the molecular details of aberrant DNA damage responses in ADPKD is ongoing and holds promise for targeted therapies.

For better or worse: crosstalk of parvovirus and host DNA damage response

Parvoviruses are a group of non-enveloped DNA viruses that have a broad spectrum of natural infections, making them important in public health. NS1 is the largest and most complex non-structural protein in the parvovirus genome, which is indispensable in the life cycle of parvovirus and is closely related to viral replication, induction of host cell apoptosis, cycle arrest, DNA damage response (DDR), and other processes. Parvovirus activates and utilizes the DDR pathway to promote viral replication through NS1, thereby increasing pathogenicity to the host cells. Here, we review the latest progress of parvovirus in regulating host cell DDR during the parvovirus lifecycle and discuss the potential of cellular consequences of regulating the DDR pathway, targeting to provide the theoretical basis for further elucidation of the pathogenesis of parvovirus and development of new antiviral drugs.

Decline of DNA damage response along with myogenic differentiation

DNA integrity is incessantly confronted to agents inducing DNA lesions. All organisms are equipped with a network of DNA damage response mechanisms that will repair DNA lesions and restore proper cellular activities. Despite DNA repair mechanisms have been revealed in replicating cells, still little is known about how DNA lesions are repaired in postmitotic cells. Muscle fibers are highly specialized postmitotic cells organized in syncytia and they are vulnerable to age-related degeneration and atrophy after radiotherapy treatment. We have studied the DNA repair capacity of muscle fiber nuclei and compared it with the one measured in proliferative myoblasts here. We focused on the DNA repair mechanisms that correct ionizing radiation (IR)-induced lesions, namely the base excision repair, the nonhomologous end joining, and the homologous recombination (HR). We found that in the most differentiated myogenic cells, myotubes, these DNA repair mechanisms present weakened kinetics of recruitment of DNA repair proteins to IR-damaged DNA. For base excision repair and HR, this decline can be linked to reduced steady-state levels of key proteins involved in these processes.

The molecular mechanism of aging and the role in neurodegenerative diseases

Aging is a complex and inevitable biological process affected by a combination of external environmental and genetic factors. Humans are currently living longer than ever before, accompanied with aging-related alterations such as diminished autophagy, decreased immunological function, mitochondrial malfunction, stem cell failure, accumulation of somatic and mitochondrial DNA mutations, loss of telomere, and altered nutrient metabolism. Aging leads to a decline in body functions and age-related diseases, for example, Alzheimer's disease, which adversely affects human health and longevity. The quality of life of the elderly is greatly diminished by the increase in their life expectancy rather than healthy life expectancy. With the rise in the age of the global population, aging and related diseases have become the focus of attention worldwide. In this review, we discuss several major mechanisms of aging, including DNA damage and repair, free radical oxidation, telomeres and telomerase, mitochondrial damage, inflammation, and their role in neurodegenerative diseases to provide a reference for the prevention of aging and its related diseases.

Whole-Genome Sequencing Analyses Reveal the Whip-like Tail Formation, Innate Immune Evolution, and DNA Repair Mechanisms of Eupleurogrammus muticus

Smallhead hairtail (Eupleurogrammus muticus) is an important marine economic fish distributed along the northern Indian Ocean and the northwest Pacific coast; however, little is known about the mechanism of its genetic evolution. This study generated the first genome assembly of E. muticus at the chromosomal level using a combination of PacBio SMRT, Illumina Nova-Seq, and Hi-C technologies. The final assembled genome size was 709.27 Mb, with a contig N50 of 25.07 Mb, GC content of 40.81%, heterozygosity rate of 1.18%, and repetitive sequence rate of 35.43%. E. muticus genome contained 21,949 protein-coding genes (97.92% of the genes were functionally annotated) and 24 chromosomes. There were 143 expansion gene families, 708 contraction gene families, and 4888 positively selected genes in the genome. Based on the comparative genomic analyses, we screened several candidate genes and pathways related to whip-like tail formation, innate immunity, and DNA repair in E. muticus. These findings preliminarily reveal some molecular evolutionary mechanisms of E. muticus at the genomic level and provide important reference genomic data for the genetic studies of other trichiurids.

Notch-3 affects chemoresistance in colorectal cancer via DNA base excision repair enzymes

Colon cancer is the second leading cause of cancer death. With over 153,000 new CRC cases predicted, it is the third most commonly diagnosed cancer. Early detection can lead to curative surgical intervention, but recurrent and late metastatic disease is frequently treated with chemotherapeutic options based on induction of DNA damage. Understanding mechanism(s) that regulate DNA damage repair within colon tumor cells is essential to developing effective therapeutic strategies. The Notch signaling pathway is known to participate in normal colon development and we have recently described a pathway by which Notch-1, Notch-3 and Smad may regulated EMT and stem-like properties in colon tumor cells, promoting tumorigenesis. Little is known about how Notch may regulate drug resistance. In this study, we used shRNA to generate colon tumor cells with loss of Notch-3 expression. These cells exhibited reduced expression of the base-excision repair proteins PARP1 and APE1, along with increased sensitivity to ara-c and cisplatin. These data point to a pathway in which Notch-3 signaling can regulate DNA repair within colon tumor cells and suggests that targeting Notch-3 may be an effective approach to rendering colon tumors sensitive to chemotherapeutic drugs.

Molecular Dynamics Investigations of Human DNA-Topoisomerase I Interacting with Novel Dewar Valence Photo-Adducts: Insights into Inhibitory Activity

Chronic exposure to ultraviolet (UV) radiation is known to induce the formation of DNA photo-adducts, including cyclobutane pyrimidine dimers (CPDs) and Dewar valence derivatives (DVs). While CPDs usually occur at higher frequency than DVs, recent studies have shown that the latter display superior selectivity and significant stability in interaction with the human DNA/topoisomerase 1 complex (TOP1). With the aim to deeply investigate the mechanism of interaction of DVs with TOP1, we report here four all-atom molecular dynamic simulations spanning one microsecond. These simulations are focused on the stability and conformational changes of two DNA/TOP1-DV complexes in solution, the data being compared with the biomimetic thymine dimer counterparts. Results from root-mean-square deviation (RMSD) and root-mean-square fluctuation (RMSF) analyses unequivocally confirmed increased stability of the DNA/TOP1-DV complexes throughout the simulation duration. Detailed interaction analyses, uncovering the presence of salt bridges, hydrogen bonds, water-mediated interactions, and hydrophobic interactions, as well as pinpointing the non-covalent interactions within the complexes, enabled the identification of specific TOP1 residues involved in the interactions over time and suggested a potential TOP1 inhibition mechanism in action.

Detection of oxaliplatin- and cisplatin-DNA lesions requires different global genome repair mechanisms that affect their clinical efficacy

The therapeutic efficacy of cisplatin and oxaliplatin depends on the balance between the DNA damage induction and the DNA damage response of tumor cells. Based on clinical evidence, oxaliplatin is administered to cisplatin-unresponsive cancers, but the underlying molecular causes for this tumor specificity are not clear. Hence, stratification of patients based on DNA repair profiling is not sufficiently utilized for treatment selection. Using a combination of genetic, transcriptomics and imaging approaches, we identified factors that promote global genome nucleotide excision repair (GG-NER) of DNA-platinum adducts induced by oxaliplatin, but not by cisplatin. We show that oxaliplatin-DNA lesions are a poor substrate for GG-NER initiating factor XPC and that DDB2 and HMGA2 are required for efficient binding of XPC to oxaliplatin lesions and subsequent GG-NER initiation. Loss of DDB2 and HMGA2 therefore leads to hypersensitivity to oxaliplatin but not to cisplatin. As a result, low DDB2 levels in different colon cancer cells are associated with GG-NER deficiency and oxaliplatin hypersensitivity. Finally, we show that colon cancer patients with low DDB2 levels have a better prognosis after oxaliplatin treatment than patients with high DDB2 expression. We therefore propose that DDB2 is a promising predictive marker of oxaliplatin treatment efficiency in colon cancer.

Targeting mitotic regulators in cancer as a strategy to enhance immune recognition

Eukaryotic DNA has evolved to be enclosed within the nucleus to protect the cellular genome from autoinflammatory responses driven by the immunogenic nature of cytoplasmic DNA. Cyclic GMP-AMP Synthase (cGAS) is the cytoplasmic dsDNA sensor, which upon activation of Stimulator of Interferon Genes (STING), mediates production of pro-inflammatory interferons (IFNs) and interferon stimulated genes (ISGs). However, although this pathway is crucial in detection of viral and microbial genetic material, cytoplasmic DNA is not always of foreign origin. It is now recognised that specifically in genomic instability, a hallmark of cancer, extranuclear material in the form of micronuclei (MN) can be generated as a result of unresolved DNA lesions during mitosis. Activation of cGAS-STING in cancer has been shown to regulate numerous tumour-immune interactions such as acquisition of 'immunologically hot' phenotype which stimulates immune-mediated elimination of transformed cells. Nonetheless, a significant percentage of poorly prognostic cancers is 'immunologically cold'. As this state has been linked with low proportion of tumour-infiltrating lymphocytes (TILs), improving immunogenicity of cold tumours could be clinically relevant by exhibiting synergy with immunotherapy. This review aims to present how inhibition of vital mitotic regulators could provoke cGAS-STING response in cancer and improve the efficacy of current immunotherapy regimens.

Nucleolar reorganization after cellular stress is orchestrated by SMN shuttling between nuclear compartments

Spinal muscular atrophy is an autosomal recessive neuromuscular disease caused by mutations in the multifunctional protein Survival of Motor Neuron, or SMN. Within the nucleus, SMN localizes to Cajal bodies, which are associated with nucleoli, nuclear organelles dedicated to the first steps of ribosome biogenesis. The highly organized structure of the nucleolus can be dynamically altered by genotoxic agents. RNAP1, Fibrillarin, and nucleolar DNA are exported to the periphery of the nucleolus after genotoxic stress and, once DNA repair is fully completed, the organization of the nucleolus is restored. We find that SMN is required for the restoration of the nucleolar structure after genotoxic stress. During DNA repair, SMN shuttles from the Cajal bodies to the nucleolus. This shuttling is important for nucleolar homeostasis and relies on the presence of Coilin and the activity of PRMT1.

DNA Damage Responses, the Trump Card of Stem Cells in the Survival Game

Stem cells, as a group of undifferentiated cells, are enriched with self-renewal and high proliferative capacity, which have attracted the attention of many researchers as a promising approach in the treatment of many diseases over the past years. However, from the cellular and molecular point of view, the DNA repair system is one of the biggest challenges in achieving therapeutic goals through stem cell technology. DNA repair mechanisms are an advantage for stem cells that are constantly multiplying to deal with various types of DNA damage. However, this mechanism can be considered a trump card in the game of cell survival and treatment resistance in cancer stem cells, which can hinder the curability of various types of cancer. Therefore, getting a deep insight into the DNA repair system can bring researchers one step closer to achieving major therapeutic goals. The remarkable thing about the DNA repair system is that this system is not only under the control of genetic factors, but also under the control of epigenetic factors. Therefore, it is necessary to investigate the role of the DNA repair system in maintaining the survival of cancer stem cells from both aspects.

DNA damage and repair: underlying mechanisms leading to microcephaly

DNA-damaging agents and endogenous DNA damage constantly harm genome integrity. Under genotoxic stress conditions, the DNA damage response (DDR) machinery is crucial in repairing lesions and preventing mutations in the basic structure of the DNA. Different repair pathways are implicated in the resolution of such lesions. For instance, the non-homologous DNA end joining and homologous recombination pathways are central cellular mechanisms by which eukaryotic cells maintain genome integrity. However, defects in these pathways are often associated with neurological disorders, indicating the pivotal role of DDR in normal brain development. Moreover, the brain is the most sensitive organ affected by DNA-damaging agents compared to other tissues during the prenatal period. The accumulation of lesions is believed to induce cell death, reduce proliferation and premature differentiation of neural stem and progenitor cells, and reduce brain size (microcephaly). Microcephaly is mainly caused by genetic mutations, especially genes encoding proteins involved in centrosomes and DNA repair pathways. However, it can also be induced by exposure to ionizing radiation and intrauterine infections such as the Zika virus. This review explains mammalian cortical development and the major DNA repair pathways that may lead to microcephaly when impaired. Next, we discuss the mechanisms and possible exposures leading to DNA damage and p53 hyperactivation culminating in microcephaly.

The mechanistic role of cardiac glycosides in DNA damage response and repair signaling

Cardiac glycosides (CGs) are a class of bioactive organic compounds well-known for their application in treating heart disease despite a narrow therapeutic window. Considerable evidence has demonstrated the potential to repurpose CGs for cancer treatment. Chemical modification of these CGs has been utilized in attempts to increase their anti-cancer properties; however, this has met limited success as their mechanism of action is still speculative. Recent studies have identified the DNA damage response (DDR) pathway as a target of CGs. DDR serves to coordinate numerous cellular pathways to initiate cell cycle arrest, promote DNA repair, regulate replication fork firing and protection, or induce apoptosis to avoid the survival of cells with DNA damage or cells carrying mutations. Understanding the modus operandi of cardiac glycosides will provide critical information to better address improvements in potency, reduced toxicity, and the potential to overcome drug resistance. This review summarizes recent scientific findings of the molecular mechanisms of cardiac glycosides affecting the DDR signaling pathway in cancer therapeutics from 2010 to 2022. We focus on the structural and functional differences of CGs toward identifying the critical features for DDR targeting of these agents.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

MNX1 facilitates the malignant progress of lung adenocarcinoma through transcriptionally upregulating CCDC34

Lung adenocarcinoma (LUAD) represents the most prevalent subtype of lung cancer and typically has high incidence and fatality rates. Motor neuron and pancreas homeobox 1 (MNX1) and coiled-coil domain-containing 34 (CCDC34) serve as oncogenes in multiple types of cancer. However, their role in LUAD remains to be elucidated. In the present study, bioinformatics analysis and LUAD cell lines were adopted to examine the expression of MNX1 and CCDC34. The proliferation, migration and invasion abilities of A549 cells were determined using Cell Counting Kit-8, colony formation, wound-healing and Transwell assay, and flow cytometry was conducted to assess cell cycle distribution and apoptosis. The interaction between MNX1 and CCDC34 was verified by luciferase reporter and chromatin immunoprecipitation assays. In addition, an in vivo animal model of LUAD was established for validation. The results demonstrated that both MNX1 and CCDC34 were upregulated in LUAD cell lines. MNX1 knockdown significantly suppressed cell proliferation, migration and invasion, hindered cell cycle progression and promoted cell apoptosis in vitro and inhibited tumor growth in vivo. However, the antitumor effect of MNX1 knockdown was weakened by simultaneous CCDC34 overexpression in vitro. In terms of mechanism, MNX1 was demonstrated to directly bind to the CCDC34 promoter and transcriptionally activate CCDC34 expression. In conclusion, the present study highlighted a critical role of the MNX1/CCDC34 axis in regulating LUAD progression, providing novel therapeutic targets for LUAD treatment.

Structures of 9-1-1 DNA checkpoint clamp loading at gaps from start to finish and ramification on biology

Rad24-RFC (replication factor C) loads the 9-1-1 checkpoint clamp onto the recessed 5' ends by binding a 5' DNA at an external surface site and threading the 3' single-stranded DNA (ssDNA) into 9-1-1. We find here that Rad24-RFC loads 9-1-1 onto DNA gaps in preference to a recessed 5' end, thus presumably leaving 9-1-1 on duplex 3' ss/double-stranded DNA (dsDNA) after Rad24-RFC ejects from DNA. We captured five Rad24-RFC-9-1-1 loading intermediates using a 10-nt gap DNA. We also determined the structure of Rad24-RFC-9-1-1 using a 5-nt gap DNA. The structures reveal that Rad24-RFC is unable to melt DNA ends and that a Rad24 loop limits the dsDNA length in the chamber. These observations explain Rad24-RFC's preference for a preexisting gap of over 5-nt ssDNA and suggest a direct role of the 9-1-1 in gap repair with various TLS (trans-lesion synthesis) polymerases in addition to signaling the ATR kinase.

The bridge between cell survival and cell death: reactive oxygen species-mediated cellular stress

As a requirement of aerobic metabolism, regulation of redox homeostasis is indispensable for the continuity of living homeostasis and life. Since the stability of the redox state is necessary for the maintenance of the biological functions of the cells, the balance between the pro-oxidants, especially ROS and the antioxidant capacity is kept in balance in the cells through antioxidant defense systems. The pleiotropic transcription factor, Nrf2, is the master regulator of the antioxidant defense system. Disruption of redox homeostasis leads to oxidative and reductive stress, bringing about multiple pathophysiological conditions. Oxidative stress characterized by high ROS levels causes oxidative damage to biomolecules and cell death, while reductive stress characterized by low ROS levels disrupt physiological cell functions. The fact that ROS, which were initially attributed as harmful products of aerobic metabolism, at the same time function as signal molecules at non-toxic levels and play a role in the adaptive response called mithormesis points out that ROS have a dose-dependent effect on cell fate determination. See also Figure 1(Fig. 1).

C11orf54 promotes DNA repair via blocking CMA-mediated degradation of HIF1A

C11orf54 is an ester hydrolase highly conserved across different species. C11orf54 has been identified as a biomarker protein of renal cancers, but its exact function remains poorly understood. Here we demonstrate that C11orf54 knockdown decreases cell proliferation and enhances cisplatin-induced DNA damage and apoptosis. On the one hand, loss of C11orf54 reduces Rad51 expression and nuclear accumulation, which results in suppression of homologous recombination repair. On the other hand, C11orf54 and HIF1A competitively interact with HSC70, knockdown of C11orf54 promotes HSC70 binding to HIF1A to target it for degradation via chaperone-mediated autophagy (CMA). C11orf54 knockdown-mediated HIF1A degradation reduces the transcription of ribonucleotide reductase regulatory subunit M2 (RRM2), which is a rate-limiting RNR enzyme for DNA synthesis and DNA repair by producing dNTPs. Supplement of dNTPs can partially rescue C11orf54 knockdown-mediated DNA damage and cell death. Furthermore, we find that Bafilomycin A1, an inhibitor of both macroautophagy and chaperone-mediated autophagy, shows similar rescue effects as dNTP treatment. In summary, we uncover a role of C11orf54 in regulating DNA damage and repair through CMA-mediated decreasing of HIF1A/RRM2 axis.

Identification of new modulator of DNA repairing pathways based on natural product (±)-peharmaline A

The complex heterogenic environment of tumour mass often leads to drug resistance and facilitate chemo insensitivity triggering more malignant phenotypes among cancer patients. Major DNA-damaging cancer drugs have been consistently proven unsuccessful in terms of elevating chemo-resistance. (±)-peharmaline A, a hybrid natural product isolated from seeds of Peganum harmala L. possesses significant cytotoxic activities. Herein, we have described the design, and synthesis of a novel library of close and simplified analogues around the anticancer natural product (±)-peharmaline A and investigated their cytotoxic activities, which led to the identification of three structurally simplified lead compounds exhibiting better potency than parent natural product. Among them, demethoxy analogue of peharmaline A was further investigated for its anticancer potential eliciting demethoxy analogue as potent DNA-damage inducing agent attenuating the expression of the proteins responsible for the DNA damage repair. Therefore, this demethoxy analogue warrants detailed investigations for the confirmations of the molecular mechanism-based studies responsible for its anticancer activity. ______________________________________________________________________________.

Structures of 9-1-1 DNA checkpoint clamp loading at gaps from start to finish and ramification to biology

Recent structural studies show the Rad24-RFC loads the 9-1-1 checkpoint clamp onto a recessed 5' end by binding the 5' DNA on Rad24 at an external surface site and threading the 3' ssDNA into the well-established internal chamber and into 9-1-1. We find here that Rad24-RFC loads 9-1-1 onto DNA gaps in preference to a recessed 5' DNA end, thus presumably leaving 9-1-1 on a 3' ss/ds DNA after Rad24-RFC ejects from the 5' gap end and may explain reports of 9-1-1 directly functioning in DNA repair with various TLS polymerases, in addition to signaling the ATR kinase. To gain a deeper understanding of 9-1-1 loading at gaps we report high-resolution structures of Rad24-RFC during loading of 9-1-1 onto 10-nt and 5-nt gapped DNAs. At a 10-nt gap we captured five Rad24-RFC-9-1-1 loading intermediates in which the 9-1-1 DNA entry gate varies from fully open to fully closed around DNA using ATPγS, supporting the emerging view that ATP hydrolysis is not needed for clamp opening/closing, but instead for dissociation of the loader from the clamp encircling DNA. The structure of Rad24-RFC-9-1-1 at a 5-nt gap shows a 180° axially rotated 3'-dsDNA which orients the template strand to bridge the 3'- and 5'- junctions with a minimum 5-nt ssDNA. The structures reveal a unique loop on Rad24 that limits the length of dsDNA in the inner chamber, and inability to melt DNA ends unlike RFC, thereby explaining Rad24-RFC's preference for a preexisting ssDNA gap and suggesting a direct role in gap repair in addition to its checkpoint role.

Synthetic lethality prediction in DNA damage repair, chromatin remodeling and the cell cycle using multi-omics data from cell lines and patients

Discovering synthetic lethal (SL) gene partners of cancer genes is an important step in developing cancer therapies. However, identification of SL interactions is challenging, due to a large number of possible gene pairs, inherent noise and confounding factors in the observed signal. To discover robust SL interactions, we devised SLIDE-VIP, a novel framework combining eight statistical tests, including a new patient data-based test iSurvLRT. SLIDE-VIP leverages multi-omics data from four different sources: gene inactivation cell line screens, cancer patient data, drug screens and gene pathways. We applied SLIDE-VIP to discover SL interactions between genes involved in DNA damage repair, chromatin remodeling and cell cycle, and their potentially druggable partners. The top 883 ranking SL candidates had strong evidence in cell line and patient data, 250-fold reducing the initial space of 200K pairs. Drug screen and pathway tests provided additional corroboration and insights into these interactions. We rediscovered well-known SL pairs such as RB1 and E2F3 or PRKDC and ATM, and in addition, proposed strong novel SL candidates such as PTEN and PIK3CB. In summary, SLIDE-VIP opens the door to the discovery of SL interactions with clinical potential. All analysis and visualizations are available via the online SLIDE-VIP WebApp.

Redox dysregulation as a driver for DNA damage and its relationship to neurodegenerative diseases

Redox homeostasis refers to the balance between the production of reactive oxygen species (ROS) as well as reactive nitrogen species (RNS), and their elimination by antioxidants. It is linked to all important cellular activities and oxidative stress is a result of imbalance between pro-oxidants and antioxidant species. Oxidative stress perturbs many cellular activities, including processes that maintain the integrity of DNA. Nucleic acids are highly reactive and therefore particularly susceptible to damage. The DNA damage response detects and repairs these DNA lesions. Efficient DNA repair processes are therefore essential for maintaining cellular viability, but they decline considerably during aging. DNA damage and deficiencies in DNA repair are increasingly described in age-related neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. Furthermore, oxidative stress has long been associated with these conditions. Moreover, both redox dysregulation and DNA damage increase significantly during aging, which is the biggest risk factor for neurodegenerative diseases. However, the links between redox dysfunction and DNA damage, and their joint contributions to pathophysiology in these conditions, are only just emerging. This review will discuss these associations and address the increasing evidence for redox dysregulation as an important and major source of DNA damage in neurodegenerative disorders. Understanding these connections may facilitate a better understanding of disease mechanisms, and ultimately lead to the design of better therapeutic strategies based on preventing both redox dysregulation and DNA damage.

BRD4: New Hope in the Battle Against Glioblastoma

The BET family proteins, comprising BRD2, BRD3 and BRD4, represent epigenetic readers of acetylated histone marks that play pleiotropic roles in the tumorigenesis and growth of multiple human malignancies, including glioblastoma (GBM). A growing body of investigation has proven BET proteins as valuable therapeutic targets for cancer treatment. Recently, several BRD4 inhibitors and degraders have been reported to successfully suppress GBM in preclinical and clinical studies. However, the precise role and mechanism of BRD4 in the pathogenesis of GBM have not been fully elucidated or summarized. This review focuses on summarizing the roles and mechanisms of BRD4 in the context of the initiation and development of GBM. In addition, several BRD4 inhibitors have been evaluated for therapeutic purposes as monotherapy or in combination with chemotherapy, radiotherapy, and immune therapies. Here, we provide a critical appraisal of studies evaluating various BRD4 inhibitors and degraders as novel treatment strategies against GBM.

Cytosolic DNA sensors and glial responses to endogenous DNA

Genomic instability is a key driving force for the development and progression of many neurodegenerative diseases and central nervous system (CNS) cancers. The initiation of DNA damage responses is a critical step in maintaining genomic integrity and preventing such diseases. However, the absence of these responses or their inability to repair genomic or mitochondrial DNA damage resulting from insults, including ionizing radiation or oxidative stress, can lead to an accumulation of self-DNA in the cytoplasm. Resident CNS cells, such as astrocytes and microglia, are known to produce critical immune mediators following CNS infection due to the recognition of pathogen and damage-associated molecular patterns by specialized pattern recognition receptors (PRRs). Recently, multiple intracellular PRRs, including cyclic GMP-AMP synthase, interferon gamma-inducible 16, absent in melanoma 2, and Z-DNA binding protein, have been identified as cytosolic DNA sensors and to play critical roles in glial immune responses to infectious agents. Intriguingly, these nucleic acid sensors have recently been shown to recognize endogenous DNA and trigger immune responses in peripheral cell types. In the present review, we discuss the available evidence that cytosolic DNA sensors are expressed by resident CNS cells and can mediate their responses to the presence of self-DNA. Furthermore, we discuss the potential for glial DNA sensor-mediated responses to provide protection against tumorigenesis versus the initiation of potentially detrimental neuroinflammation that could initiate or foster the development of neurodegenerative disorders. Determining the mechanisms that underlie the detection of cytosolic DNA by glia and the relative role of each pathway in the context of specific CNS disorders and their stages may prove pivotal in our understanding of the pathogenesis of such conditions and might be leveraged to develop new treatment modalities.

Exploring SPK98 for the Selective Sensitization of ATM- or P53-Deficient Cancer Cells

Frequent mutation in the ATM/P53 signaling pathway has been documented in many human cancers. Reportedly, cancer cells with deficient P53/ATM pathways depend on functional Ataxia-telangiectasia and Rad3-related (ATR) protein for survival. This has prompted research in developing ATR inhibitors for the selective sensitization of cancer cells that are P53/ATM-deficient, but no clinical success has been attained thus far. This study explores the therapeutic potential of SPK98, an analogue of Torin2 in P53- and ATM-deficient cancer cells. Furthermore, the prospect of improving the therapeutic outcome of the genotoxic agent was also explored. SPK98 was shown to inhibit full-length human ATR protein purified from HEK293T cells. Cellular investigation using SPK98 demonstrated that it selectively sensitizes P53- and ATM-deficient cells at low concentrations compared to P53-/ATM-proficient cells. Furthermore, SPK98 drives the cancer cells toward cell death by promoting the formation of DNA double-strand breaks. Taken together, our findings suggest that SPK98 is a promising therapeutic molecule for P53- or ATM-deficient malignancy that merits additional preclinical investigation.

DNA Damage Response-Associated Cell Cycle Re-Entry and Neuronal Senescence in Brain Aging and Alzheimer's Disease

Chronological aging is by far the strongest risk factor for age-related dementia and Alzheimer's disease. Senescent cells accumulated in the aging and Alzheimer's disease brains are now recognized as the keys to describing such an association. Cellular senescence is a classic phenomenon characterized by stable cell arrest, which is thought to be applicable only to dividing cells. Emerging evidence indicates that fully differentiated post-mitotic neurons are also capable of becoming senescent, with roles in contributing to both brain aging and disease pathogenesis. The key question that arises is the identity of the upstream triggers and the molecular mechanisms that underly such changes. Here, we highlight the potential role of persistent DNA damage response as the major driver of senescent phenotypes and discuss the current evidence and molecular mechanisms that connect DNA repair infidelity, cell cycle re-entry and terminal fate decision in committing neuronal cell senescence.

DNA Damage Response in Cancer Therapy and Resistance: Challenges and Opportunities

Resistance to chemo- and radiotherapy is a common event among cancer patients and a reason why new cancer therapies and therapeutic strategies need to be in continuous investigation and development. DNA damage response (DDR) comprises several pathways that eliminate DNA damage to maintain genomic stability and integrity, but different types of cancers are associated with DDR machinery defects. Many improvements have been made in recent years, providing several drugs and therapeutic strategies for cancer patients, including those targeting the DDR pathways. Currently, poly (ADP-ribose) polymerase inhibitors (PARP inhibitors) are the DDR inhibitors (DDRi) approved for several cancers, including breast, ovarian, pancreatic, and prostate cancer. However, PARPi resistance is a growing issue in clinical settings that increases disease relapse and aggravate patients' prognosis. Additionally, resistance to other DDRi is also being found and investigated. The resistance mechanisms to DDRi include reversion mutations, epigenetic modification, stabilization of the replication fork, and increased drug efflux. This review highlights the DDR pathways in cancer therapy, its role in the resistance to conventional treatments, and its exploitation for anticancer treatment. Biomarkers of treatment response, combination strategies with other anticancer agents, resistance mechanisms, and liabilities of treatment with DDR inhibitors are also discussed.

Genotoxic Effect of Cadmium and Zinc in the Peripheral Erythrocytes of Prussian Carp (Carassius Gibelio B.)

Introduction

Cadmium and zinc are often found in aquatic environment and may accumulate in living organisms. The aim of this study was to evaluate the genotoxic effect of Cd, Zn, and their binary mixture on the peripheral blood erythrocytes of Prussian carp (Carassius gibelio B.).

Material and Methods

The fish were exposed to 4.0 mg/L Cd, 4.0 mg/L Zn or a mixture of 4.0 mg/L Cd and 4.0 mg/L Zn for a period of 14, 21 or 28 days. Genotoxic effects were investigated in peripheral blood cells using the comet assay and the erythrocyte micronucleus assay.

Results

The results demonstrated that the frequencies of micronuclei (MN) and both nuclear and cellular abnormalities in erythrocytes were significantly higher in all exposure groups as compared to the control group. The fish exposed to the mixture of Cd and Zn presented the highest frequency of MN. Furthermore, there was a decrease in the frequency of MN and an increase in the occurrence of DNA integrity defects (DNA damage) with longer time of exposure to the metals studied.

Conclusion

Erythrocyte micronucleus and comet assays confirmed the genotoxicity of Cd and Zn. The results of the tests applied (which showed considerable variability) suggest the involvement of various toxicity mechanisms. Therefore, an integrative and comprehensive approach, using a set of assays for toxicity profile determination, should be adopted during ecotoxicological studies and environmental risk assessment pertaining to these elements.

Nuclear antiviral innate responses at the intersection of DNA sensing and DNA repair

The coevolution of vertebrate and mammalian hosts with DNA viruses has driven the ability of host cells to distinguish viral from cellular DNA in the nucleus to induce intrinsic immune responses. Concomitant viral mechanisms have arisen to inhibit DNA sensing. At this virus-host interface, emerging evidence links cytokine responses and cellular homeostasis pathways, particularly the DNA damage response (DDR). Nuclear DNA sensors, such as the interferon (IFN)-γ inducible protein 16 (IFI16), functionally intersect with the DDR regulators ataxia telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNA-PK). Here, we discuss accumulating knowledge for the DDR-innate immunity signaling axis. Through the lens of this infection-driven signaling axis, we present host and viral molecular strategies acquired to regulate autoinflammation and antiviral responses.

Chalcone-Acridine Hybrid Suppresses Melanoma Cell Progression via G2/M Cell Cycle Arrest, DNA Damage, Apoptosis, and Modulation of MAP Kinases Activity

This study was focused on investigating the antiproliferative effects of chalcone hybrids in melanoma cancer cells. Among seven chalcone hybrids, the chalcone-acridine hybrid 1C was the most potent and was selected for further antiproliferative mechanism studies. This in vitro study revealed the potent antiproliferative effect of 1C via cell cycle arrest and apoptosis induction. Cell cycle arrest at the G2/M phase was associated with modulation of expression or phosphorylation of specific cell cycle-associated proteins (cyclin B1, p21, and ChK1), tubulins, as well as with the activation of the DNA damage response pathway. Chalcone 1C also induced apoptosis accompanied by mitochondrial dysfunction evidenced by a decrease in mitochondrial membrane potential, increase in Bax/Bcl-xL ratio and cytochrome c release followed by caspase 3/7 activation. In addition, increased phosphorylation of MAP kinases (Erk1/2, p38 and JNK) was observed in chalcone 1C-treated melanoma cells. The strong antiproliferative activities of this chalcone-acridine hybrid suggest that it may be useful as an antimelanoma agent in humans.

DNA damage checkpoint execution and the rules of its disengagement

Chromosomes are susceptible to damage during their duplication and segregation or when exposed to genotoxic stresses. Left uncorrected, these lesions can result in genomic instability, leading to cells’ diminished fitness, unbridled proliferation or death. To prevent such fates, checkpoint controls transiently halt cell cycle progression to allow time for the implementation of corrective measures. Prominent among these is the DNA damage checkpoint which operates at G2/M transition to ensure that cells with damaged chromosomes do not enter the mitotic phase. The execution and maintenance of cell cycle arrest are essential aspects of G2/M checkpoint and have been studied in detail. Equally critical is cells’ ability to switch-off the checkpoint controls after a successful completion of corrective actions and to recommence cell cycle progression. Interestingly, when corrective measures fail, cells can mount an unusual cellular response, termed adaptation, where they escape checkpoint arrest and resume cell cycle progression with damaged chromosomes at the cost of genome instability or even death. Here, we discuss the DNA damage checkpoint, the mitotic networks it inhibits to prevent segregation of damaged chromosomes and the strategies cells employ to quench the checkpoint controls to override the G2/M arrest.

ITGB4 deficiency induces DNA damage by downregulating HDAC1 in airway epithelial cells under stress stimulation

BACKGROUND

DNA damage in airway epithelia under exogenous disruptors can trigger various pulmonary diseases. Integrin beta 4 (ITGB4) is a structural adhesion molecule, which is indicated to regulate the process of DNA damage in airway epithelia for its unique long cytoplasmic domain subunit.

METHODS

The expression level of ITGB4 and the degree of DNA damage were observed in the house dust mite (HDM)-stressed model and ozone-challenged model, respectively. Besides, ITGB4 conditional knockout mice and ITGB4-deficient airway epithelial cells were constructed to observe the influence of ITGB4 deficiency on DNA damage. Furthermore, the influence of ITGB4 deficiency on HDAC1 expression in airway epithelia was determined under stress stimulation. Finally, corresponding intervention strategies were carried out to verify the involvement of the ITGB4-mediated HDAC1 pathway in DNA damage of airway epithelial cells.

RESULTS

HDM stress and ozone challenge reduced the expression of ITGB4, which is accompanied by the increased expression of 8-oxoG and γ-H2AX both in vivo and in vitro. Moreover, ITGB4 deficiency in airway epithelia aggravates the degree of DNA damage under HDM stimulation and ozone stress, respectively. Furthermore, ITGB4 deficiency downregulated the expression of HDAC1 during DNA damage, and restoring HDAC1 can reverse the enhanced DNA damage in airway epithelial cells after exogenous stress.

CONCLUSIONS

This study confirmed the involvement of ITGB4 in the regulation of DNA damage through mediating HDAC1 in airway epithelial cells under exogenous stress. These results supply some useful insights into the mechanism of DNA damage in airway epithelial cells, which would provide possible targets for early prediction and intervention of pulmonary diseases.

Prognostic Impact of TP53 Mutations and Tumor Mutational Load in Colorectal Cancer

The DNA damage response (DDR) is critical for maintaining genome stability, and abnormal DDR—resulting from mutations in DNA damage-sensing and repair proteins—is a hallmark of cancer. Here, we aimed to investigate the predictive power of DDR gene mutations and the tumor mutational load (TML) for survival outcomes in a cohort of 22 rectal cancer patients who received pre-operative neoadjuvant therapy. Univariate analysis revealed that TML-high and TP53 mutations were significantly associated with worse overall survival (OS) with TML-high retaining significance in multivariate analyses. Kaplan–Meier survival analyses further showed TML-high was associated with worse disease-free (p = 0.036) and OS (p = 0.024) results in our patient cohort. A total of 53 somatic mutations were identified in 22 samples with eight (36%) containing mutations in DDR genes, including ATM, ATR, CHEK2, MRE11A, RAD50, NBN, ERCC2 and TP53. TP53 was the most frequently mutated gene, and TP53 mutations were significantly associated with worse OS (p = 0.023) in Kaplan–Meier survival analyses. Thus, our data indicate that TML and TP53 mutations have prognostic value for rectal cancer patients and may be important independent biomarkers for patient management. This suggests that prognostic determination for rectal cancer patients receiving pre-operative neoadjuvant therapy should include consideration of the initial TML and tumor genetic status.

XAB2 dynamics during DNA damage-dependent transcription inhibition

Xeroderma Pigmentosum group A-binding protein 2 (XAB2) is a multifunctional protein playing a critical role in distinct cellular processes including transcription, splicing, DNA repair, and messenger RNA export. In this study, we demonstrate that XAB2 is involved specifically and exclusively in Transcription-Coupled Nucleotide Excision Repair (TC-NER) reactions and solely for RNA polymerase 2 (RNAP2)-transcribed genes. Surprisingly, contrary to all the other NER proteins studied so far, XAB2 does not accumulate on the local UV-C damage; on the contrary, it becomes more mobile after damage induction. XAB2 mobility is restored when DNA repair reactions are completed. By scrutinizing from which cellular complex/partner/structure XAB2 is released, we have identified that XAB2 is detached after DNA damage induction from DNA:RNA hybrids, commonly known as R-loops, and from the CSA and XPG proteins. This release contributes to the DNA damage recognition step during TC-NER, as in the absence of XAB2, RNAP2 is blocked longer on UV lesions. Moreover, we also demonstrate that XAB2 has a role in retaining RNAP2 on its substrate without any DNA damage.

The role of USP51 in attenuating chemosensitivity of lung cancer cells to cisplatin by regulating DNA damage response

Lung cancer is the most frequent type of cancer affecting both men and women globally, and it is associated with a high mortality rate. It is clinically treated with cisplatin, a platinum-based drug that works by generating DNA lesions, which activates DNA damage response and induces cell death. However, chemoresistance by cancer cells limits the clinical usefulness of cisplatin as an anticancer drug. Here, we uncovered a role of ubiquitin-specific protease USP51 in the chemosensitivity of lung cancer cells to cisplatin by regulating DNA damage response. USP51 was more upregulated in lung cancer tissues of chemotherapy-resistant patients than those of chemotherapy-sensitive patients with adjacent, non-tumor tissues. USP51 overexpression in lung cancer cells in vitro reduced γ-H2AX formation and promoted CHK1 phosphorylation, whereas USP51 knockdown showed opposite effects, indicating that USP51 played an important role in promoting DNA damage repair. Finally, USP51 knockdown weakened cisplatin resistance in A549/DDP cells and significantly suppressed tumor growth in vivo, suggesting that a USP51 inhibitor combined with cisplatin may be considered as an effective treatment strategy to eliminate drug-resistant lung cancer cells. This article is protected by copyright. All rights reserved.

Myristicin and Elemicin: Potentially Toxic Alkenylbenzenes in Food

Alkenylbenzenes represent a group of naturally occurring substances that are synthesized as secondary metabolites in various plants, including nutmeg and basil. Many of the alkenylbenzene-containing plants are common spice plants and preparations thereof are used for flavoring purposes. However, many alkenylbenzenes are known toxicants. For example, safrole and methyleugenol were classified as genotoxic carcinogens based on extensive toxicological evidence. In contrast, reliable toxicological data, in particular regarding genotoxicity, carcinogenicity, and reproductive toxicity is missing for several other structurally closely related alkenylbenzenes, such as myristicin and elemicin. Moreover, existing data on the occurrence of these substances in various foods suffer from several limitations. Together, the existing data gaps regarding exposure and toxicity cause difficulty in evaluating health risks for humans. This review gives an overview on available occurrence data of myristicin, elemicin, and other selected alkenylbenzenes in certain foods. Moreover, the current knowledge on the toxicity of myristicin and elemicin in comparison to their structurally related and well-characterized derivatives safrole and methyleugenol, especially with respect to their genotoxic and carcinogenic potential, is discussed. Finally, this article focuses on existing data gaps regarding exposure and toxicity currently impeding the evaluation of adverse health effects potentially caused by myristicin and elemicin.

DNA double-strand break repair and nucleic acid-related immunity

DNA damage repair and innate immunity are two conserved mechanisms that both function in cellular stress responses. Recently, an increasing amount of evidence has uncovered the close relationship between these two ancient biological processes. Here, we review the classical function of factors involved in DNA repair, and especially double-strand break repair, in innate immunity; more importantly, we discuss the novel roles of DNA repair factors in regulating innate immunity and vice versa. In addition, we also review the roles of DNA repair, innate immunity and their crosstalk in human diseases, which suggest that these two pathways may be compelling targets for disease prevention and treatment.