Oncogene-Stimulated Congestion at the KEAP1 Stress Signaling Hub Allows Bypass of NRF2 and Induction of NRF2-Target Genes that Promote Tumor Survival

Inhibitor of apoptosis stimulating protein of p53 protects against MPP+-induced neurotoxicity of dopaminergic neurons

Inhibitor of apoptosis stimulating protein of p53 (iASPP) is related to the pathogenesis of several neurological disorders by affecting the oxidative stress and survival of neurons. However, whether iASPP has a role in Parkinson disease (PD) remains to be determined. This work explored the potential regulatory effect of iASPP in an in vitro model of PD based on 1-methyl-4-phenylpyridinium (MPP+)-evoked neurotoxicity of dopaminergic neurons in culture. MN9D neurons were treated with MPP+ at 200 µM in the culture media for 24 h to induce neurotoxicity. Overexpression and silencing of iASPP in neurons were achieved by infecting recombinant adenovirus expressing iASPP and sh-iASPP, respectively. Protein expression was examined by immunoblotting. MPP+-evoked neurotoxicity of dopaminergic neurons was determined by cell viability, TUNEL, and flow cytometric assays. The transcriptional activity of nuclear erythroid factor 2-like 2 (Nrf2) was assessed by luciferase reporter assay. Kelch-like ECH-associated protein 1 (Keap1)-knockout neurons were generated by lentiCRISPR/Cas9-Keap1 constructs. Expression levels of iASPP declined in MPP+-stimulated neurons. Overexpression of iASPP in neurons exhibited inhibitory effects on MPP+-evoked apoptosis, α-synuclein accumulation, and oxidative stress, while iASPP-deficient neurons were more sensitive to MPP+-induced neurotoxicity. Overexpression of iASPP led to an enhancing effect on Nrf2 activation in MPP+-stimulated neurons. Mechanism research revealed that iASPP may contribute to the activation of Nrf2 by competing with Nrf2 in binding with Keap1. Notably, the regulatory effect of iASPP on Nrf2 was diminished in Keap1-knockout neurons. The chemical inhibition of Nrf2 or knockdown of Nrf2 abrogated the protective effects of iASPP on MPP+-induced neurotoxicity. To conclude, iASPP protects dopaminergic neurons against MPP+-induced neurotoxicity through modulation of the Keap1/Nrf2 axis. Therefore, iASPP may play a crucial role in mediating the loss of dopaminergic neurons in PD, and targeting the iASPP-Nrf2 axis could be a promising strategy for treating PD.

A novel crosstalk between Nrf2 and Smad2/3 bridged by two nuanced Keap1 isoforms with their divergent effects on these distinct family transcription factors

The Keap1-Nrf2 signalling to transcriptionally regulate antioxidant response element (ARE)-driven target genes has been accepted as key redox-sensitive pathway governing a vast variety of cellular stresses during healthy survival and disease development. Herein, we identified two nuanced isoforms α and β of Keap1 in HepG2 cells, arising from its first and another in-frame translation starting codons, respectively. In identifying those differential expression genes monitored by Keap1α and/or Keap1β, an unusual interaction of Keap1 with Smad2/3 was discovered by parsing transcriptome sequencing, Keap1-interacting protein profiling and relevant immunoprecipitation data. Further examination validated that Smad2/3 enable physical interaction with Keap1, as well as its isoforms α and β, by both EDGETSD and DLG motifs in the linker regions between their MH1 and MH2 domains, such that the stability of Smad2/3 and transcriptional activity are enhanced with their prolonged half-lives and relevant signalling responses from the cytoplasmic to nuclear compartments. The activation of Smad2/3 by Keap1, Keap1α or Keap1β was much likely contributable to a coordinative or another competitive effect of Nrf2, particularly in distinct Keap1-based cellular responses to its cognate growth factor (i.e. TGF-β1) or redox stress (e.g. stimulated by tBHQ and DTT). Overall, this discovery presents a novel functional bridge crossing the Keap1-Nrf2 redox signalling and the TGF-β1-Smad2/3 pathways so as to coordinately regulate the healthy growth and development.

An Approach to Evaluate the Effective Cytoplasmic Concentration of Bioactive Agents Interacting with a Selected Intracellular Target Protein

To compare the effectiveness of various bioactive agents reversibly acting within a cell on a target intracellular macromolecule, it is necessary to assess effective cytoplasmic concentrations of the delivered bioactive agents. In this work, based on a simple equilibrium model and the cellular thermal shift assay (CETSA), an approach is proposed to assess effective concentrations of both a delivered bioactive agent and a target protein. This approach was tested by evaluating the average concentrations of nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated-protein 1 (Keap1) proteins in the cytoplasm for five different cell lines (Hepa1, MEF, RAW264.7, 3LL, and AML12) and comparing the results with known literature data. The proposed approach makes it possible to analyze both binary interactions and ternary competition systems; thus, it can have a wide application for the analysis of protein-protein or molecule-protein interactions in the cell. The concentrations of Nrf2 and Keap1 in the cell can be useful not only in analyzing the conditions for the activation of the Nrf2 system, but also for comparing the effectiveness of various drug delivery systems, where the delivered molecule is able to interact with Keap1.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

Role of NRF2 in Lung Cancer

The gene expression program induced by NRF2 transcription factor plays a critical role in cell defense responses against a broad variety of cellular stresses, most importantly oxidative stress. NRF2 stability is fine-tuned regulated by KEAP1, which drives its degradation in the absence of oxidative stress. In the context of cancer, NRF2 cytoprotective functions were initially linked to anti-oncogenic properties. However, in the last few decades, growing evidence indicates that NRF2 acts as a tumor driver, inducing metastasis and resistance to chemotherapy. Constitutive activation of NRF2 has been found to be frequent in several tumors, including some lung cancer sub-types and it has been associated to the maintenance of a malignant cell phenotype. This apparently contradictory effect of the NRF2/KEAP1 signaling pathway in cancer (cell protection against cancer versus pro-tumoral properties) has generated a great controversy about its functions in this disease. In this review, we will describe the molecular mechanism regulating this signaling pathway in physiological conditions and summarize the most important findings related to the role of NRF2/KEAP1 in lung cancer. The focus will be placed on NRF2 activation mechanisms, the implication of those in lung cancer progression and current therapeutic strategies directed at blocking NRF2 action.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

The Protective Effect of Polyherbal Formulation, Harak Formula, on UVA-Induced Photoaging of Human Dermal Fibroblasts and Mouse Skin via Promoting Nrf2-Regulated Antioxidant Defense

Polyherbal formulation combining multiple herbs is suggested to achieve enhanced therapeutic effects and reduce toxicity. Harak herbal formula (HRF) extracts were proposed to regulate skin responses to UVR through their ability to suppress UVA-induced matrix metalloproteinase-1 (MMP-1) and pigmentation via promoting antioxidant defenses in in vitro models. Therefore, natural products targeting Nrf2 (nuclear factor erythroid 2-related factor 2)-regulated antioxidant response might represent promising anti-photoaging candidates. Hesperetin (HSP) was suggested as a putative bioactive compound of the HRF, as previously shown by its chemical profiling using the liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). In this study, we explored the anti-photoaging effects of HRF extracts and HSP on normal human dermal fibroblasts (NHDFs) and mouse skin exposed to UVA irradiation. Pretreatment of NHDFs with HRF extracts and HSP protected against UVA (8 J/cm²)-mediated cytotoxicity and reactive oxygen species (ROS) formation. The HRF and HSP pretreatment also attenuated the UVA-induced MMP-1 activity and collagen depletion concomitant with an upregulation of Nrf2 activity and its downstream genes (GST and NQO-1). Moreover, our findings provided the in vivo relevance to the in vitro anti-photoaging effects of HRF as topical application of the extracts (10, 30 and 100 mg/cm²) and HSP (0.3, 1, and 3 mg/cm²) 1 h before UVA exposure 3 times per week for 2 weeks (a total dose of 60 J/cm²) mitigated MMP-1 upregulation, collagen loss in correlation with enhanced Nrf2 nuclear accumulation and its target protein GST and NQO-1 as well as reduced 8-hydroxy-2′-deoxyguanosine (8-OHdG) in irradiated mouse skin. Thus, our findings revealed that HRF extracts and HSP attenuated UVA-induced photoaging via upregulating Nrf2, together with their abilities to reduce ROS formation and oxidative damage. Our study concluded that the HRF and its bioactive ingredient HSP may represent potential candidates for preventing UVA-induced photoaging via restoration of redox balance.

Upregulation of iASPP ameliorates hypoxia/reoxygenation-induced apoptosis and oxidative stress in cardiomyocytes by upregulating Nrf2 signaling

The inhibitor of apoptosis-stimulating protein of p53 (iASPP) acts as a key modulator of cellular protection against oxidative stress. In the present work, we assessed the role of iASPP in the regulation of cardiomyocyte injury induced by hypoxia/reoxygenation (H/R). We found that H/R-exposed cardiomyocytes expressed decreased levels of iASPP. The upregulation of iASPP repressed H/R-induced injury by decreasing levels of apoptosis and reactive oxygen species production. The upregulation of iASPP increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nuclear translocation and enhanced Nrf2 activation. The overexpression of Kelch-like ECH-associated protein 1 reversed iASPP-mediated promotion of Nrf2 activation. Nrf2 inhibition abrogated iASPP-mediated cardioprotective effects in H/R-exposed cardiomyocytes. Our work demonstrates that the upregulation of iASPP ameliorates H/R-induced apoptosis and oxidative stress in cardiomyocytes via potentiating Nrf2 signaling via modulation of Keap1.

NRF2 and the Ambiguous Consequences of Its Activation during Initiation and the Subsequent Stages of Tumourigenesis

NF-E2 p45-related factor 2 (NRF2, encoded in the human by NFE2L2) mediates short-term adaptation to thiol-reactive stressors. In normal cells, activation of NRF2 by a thiol-reactive stressor helps prevent, for a limited period of time, the initiation of cancer by chemical carcinogens through induction of genes encoding drug-metabolising enzymes. However, in many tumour types, NRF2 is permanently upregulated. In such cases, its overexpressed target genes support the promotion and progression of cancer by suppressing oxidative stress, because they constitutively increase the capacity to scavenge reactive oxygen species (ROS), and they support cell proliferation by increasing ribonucleotide synthesis, serine biosynthesis and autophagy. Herein, we describe cancer chemoprevention and the discovery of the essential role played by NRF2 in orchestrating protection against chemical carcinogenesis. We similarly describe the discoveries of somatic mutations in NFE2L2 and the gene encoding the principal NRF2 repressor, Kelch-like ECH-associated protein 1 (KEAP1) along with that encoding a component of the E3 ubiquitin-ligase complex Cullin 3 (CUL3), which result in permanent activation of NRF2, and the recognition that such mutations occur frequently in many types of cancer. Notably, mutations in NFE2L2, KEAP1 and CUL3 that cause persistent upregulation of NRF2 often co-exist with mutations that activate KRAS and the PI3K-PKB/Akt pathway, suggesting NRF2 supports growth of tumours in which KRAS or PKB/Akt are hyperactive. Besides somatic mutations, NRF2 activation in human tumours can occur by other means, such as alternative splicing that results in a NRF2 protein which lacks the KEAP1-binding domain or overexpression of other KEAP1-binding partners that compete with NRF2. Lastly, as NRF2 upregulation is associated with resistance to cancer chemotherapy and radiotherapy, we describe strategies that might be employed to suppress growth and overcome drug resistance in tumours with overactive NRF2.

iASPP-Mediated ROS Inhibition Drives 5-Fu Resistance Dependent on Nrf2 Antioxidative Signaling Pathway in Gastric Adenocarcinoma

AIMS

Inhibitor for the apoptosis-stimulating protein of p53 (iASPP) has been reported to be correlated with 5-fluorouracil (5-Fu) resistance in renal cell carcinoma. Here, we uncover mechanisms of iASPP-Nrf2-ROS regulation of 5-Fu resistance which are important for the development of alternative treatment strategies for gastric adenocarcinoma treatment.

METHODS

We analyzed iASPP and Nrf2 through TCGA RNA-seq data, UALCAN analysis, and cBioPortal datasets. Intracellular ROS generation was determined by 2',7'-dichloro-fluorescin diacetate staining. Transwell was used to evaluate the invasion. The expression of iASPP, Nrf2, HO-1, and GSTP1 was tested using western blot.

RESULTS

We found that iASPP KD led to an apparent 5-Fu-induced ROS accumulation in MGC803 and SCG790 cells. Accompanied by iASPP KD, Nrf2 was markedly decreased. iASPP-induced ROS inhibition relies on Nrf2, and due to both knocked down iASPP and Nrf2, the level of ROS did not show an obvious difference with Nrf2 KD solely. Similarly, iASPP KD failed to enhance the Nrf2 KD-mediated ROS accumulation after 5-Fu treatment, suggesting that iASPP-induced antioxidative effects related to 5-Fu resistance are partially dependent on Nrf2. Also, the combination of iASPP KD and Nrf2 KD did not show any synergistic effect on apoptosis after 5-Fu treatment in MGC803 and SCG790 cells. Further studies revealed that iASPP KD or Nrf2 KD could decrease the expression of HO-1 and GSTP1.

CONCLUSIONS

Our data highlight that iASPP plays a crucial role in the inhibition of 5-Fu-induced apoptosis resistance by removing ROS accumulation in gastric adenocarcinoma, and that the removal of ROS induced by iASPP is Nrf2 signaling dependent.

High NRF2 Levels Correlate with Poor Prognosis in Colorectal Cancer Patients and with Sensitivity to the Kinase Inhibitor AT9283 In Vitro

Aberrant hyperactivation of nuclear factor erythroid 2 (NF-E2) p45-related factor 2 (NRF2) is a common event in many tumour types and associates with resistance to therapy and poor patient prognosis; however, its relevance in colorectal tumours is not well-established. Measuring the expression of surrogate genes for NRF2 activity in silico, in combination with validation in patients' samples, we show that the NRF2 pathway is upregulated in colorectal tumours and that high levels of nuclear NRF2 correlate with a poor patient prognosis. These results highlight the need to overcome the protection provided by NRF2 and present an opportunity to selectively kill cancer cells with hyperactive NRF2. Exploiting the CRISPR/Cas9 technology, we generated colorectal cancer cell lines with hyperactive NRF2 and used them to perform a drug screen. We identified AT9283, an Aurora kinase inhibitor, for its selectivity towards killing cancer cells with hyperactive NRF2 as a consequence to either genetic or pharmacological activation. Our results show that hyperactivation of NRF2 in colorectal cancer cells might present a vulnerability that could potentially be therapeutically exploited by using the Aurora kinase inhibitor AT9283.

The Pleiotropic Role of the KEAP1/NRF2 Pathway in Cancer

The unregulated proliferative capacity of many tumors is dependent on dysfunctional nutrient utilization and ROS (reactive oxygen species) signaling to sustain a deranged metabolic state. Although it is clear that cancers broadly rely on these survival and signaling pathways, how they achieve these aims varies dramatically. Mutations in the KEAP1/NRF2 pathway represent a potent cancer adaptation to exploit native cytoprotective pathways that involve both nutrient metabolism and ROS regulation. Despite activating these advantageous processes, mutations within KEAP1/ NRF2 are not universally selected for across cancers and instead appear to interact with particular tumor driver mutations and tissues of origin. Here, we highlight the relationship between the KEAP1/NRF2 signaling axis and tumor biology with a focus on genetic mutation, metabolism, immune regulation, and treatment implications and opportunities. Understanding the dysregulation of KEAP1 and NRF2 provides not only insight into a commonly mutated tumor suppressor pathway but also a window into the factors dictating the development and evolution of many cancers.

p62 promotes proliferation, apoptosis‑resistance and invasion of prostate cancer cells through the Keap1/Nrf2/ARE axis

Prostate cancer poses a public health threat to hundreds of people around the world. p62 has been identified as a tumor suppressor, however, the mechanism by which p62 promotes prostate cancer remains poorly understood. The present study aimed to investigate whether p62 promotes proliferation, apoptosis resistance and invasion of prostate cancer cells via the Kelch-like ECH-associated protein 1/nuclear factor erytheroid-derived 2-like 2/antioxidant response element (Keap1/Nrf2/ARE) axis. Immunohistochemical staining and immunoblotting were performed to determine the protein levels. Rates of proliferation, invasion and apoptosis of prostate cancer cells were assessed using an RTCA system and flow cytometric assays. Levels of reactive oxygen species (ROS) were assessed using Cell ROX Orange reagent and mRNA levels of Nrf2 target genes were detected by qRT-PCR. It was revealed that p62 increased the levels and activities of Nrf2 by suppressing Keap1-mediated proteasomal degradation in prostate cancer cells and tissues, and high levels of p62 promoted growth of prostate cancer through the Keap1/Nrf2/ARE system. Silencing of Nrf2 in DU145 cells overexpressing p62 led to decreases in the rate of cell proliferation and invasion and an increase in the rate of cell apoptosis. p62 activated the Nrf2 pathway, promoted the transcription of Nrf2-mediated target genes and suppressed ROS in prostate cancer. Therefore, p62 promoted the development of prostate cancer by activating the Keap1/Nrf2/ARE pathway and decreasing p62 may provide a new strategy to ameliorate tumor aggressiveness and suppress tumorigenesis to improve clinical outcomes.

Nestin regulates cellular redox homeostasis in lung cancer through the Keap1-Nrf2 feedback loop

Abnormal cancer antioxidant capacity is considered as a potential mechanism of tumor malignancy. Modulation of oxidative stress status is emerging as an anti-cancer treatment. Our previous studies have found that Nestin-knockdown cells were more sensitive to oxidative stress in non-small cell lung cancer (NSCLC). However, the molecular mechanism by which Nestin protects cells from oxidative damage remains unclear. Here, we identify a feedback loop between Nestin and Nrf2 maintaining the redox homeostasis. Mechanistically, the ESGE motif of Nestin interacts with the Kelch domain of Keap1 and competes with Nrf2 for Keap1 binding, leading to Nrf2 escaping from Keap1-mediated degradation, subsequently promoting antioxidant enzyme generation. Interestingly, we also map that the antioxidant response elements (AREs) in the Nestin promoter are responsible for its induction via Nrf2. Taken together, our results indicate that the Nestin-Keap1-Nrf2 axis regulates cellular redox homeostasis and confers oxidative stress resistance in NSCLC.

Therapeutic targeting of the NRF2 and KEAP1 partnership in chronic diseases

The transcription factor NF-E2 p45-related factor 2 (NRF2; encoded by NFE2L2) and its principal negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (KEAP1), are critical in the maintenance of redox, metabolic and protein homeostasis, as well as the regulation of inflammation. Thus, NRF2 activation provides cytoprotection against numerous pathologies including chronic diseases of the lung and liver; autoimmune, neurodegenerative and metabolic disorders; and cancer initiation. One NRF2 activator has received clinical approval and several electrophilic modifiers of the cysteine-based sensor KEAP1 and inhibitors of its interaction with NRF2 are now in clinical development. However, challenges regarding target specificity, pharmacodynamic properties, efficacy and safety remain.

Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) Inhibition: An Emerging Strategy in Cancer Therapy

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a pleiotropic transcription factor, especially for its complex and dual effects in cancer. With the continuous growing research, new regulatory modes and new functions of Nrf2 and tumor-promoting effects of Nrf2 in malignant transformed tumors have become increasingly clear. Accumulating evidence has established that Nrf2 contributes to the whole process of pathogenesis, progression, metastasis, and prognosis of cancer, and Nrf2 could be a promising target in cancer therapy. However, the development of Nrf2 inhibitor is still limited. In this perspective, we will briefly describe the biological function and modulating network of Nrf2, stress its oncogenic role, and point out possible ways to inhibit Nrf2, as well as summarize the reported Nrf2 inhibitors.

Keap1-MCM3 interaction is a potential coordinator of molecular machineries of antioxidant response and genomic DNA replication in metazoa

Coordination of DNA replication and cellular redox homeostasis mechanisms is essential for the sustained genome stability due to the sensitivity of replicating DNA to oxidation. However, substantial gaps remain in our knowledge of underlying molecular pathways. In this study, we characterise the interaction of Keap1, a central antioxidant response regulator in Metazoa, with the replicative helicase subunit protein MCM3. Our analysis suggests that structural determinants of the interaction of Keap1 with its critical downstream target - Nrf2 master transactivator of oxidative stress response genes – may have evolved in evolution to mimic the conserved helix-2-insert motif of MCM3. We show that this has led to a competition between MCM3 and Nrf2 proteins for Keap1 binding, and likely recruited MCM3 for the competitive binding dependent modulation of Keap1 controlled Nrf2 activities. We hypothesise that such mechanism could help to adjust the Keap1-Nrf2 antioxidant response pathway according to the proliferative and replicative status of the cell, with possible reciprocal implications also for the regulation of cellular functions of MCM3. Altogether this suggests about important role of Keap1-MCM3 interaction in the cross-talk between replisome and redox homeostasis machineries in metazoan cells.