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PubMed2005

The p53 pathway: positive and negative feedback loops.

The p53 pathway responds to stresses that can disrupt the fidelity of DNA replication and cell division. A stress signal is transmitted to the p53 protein by post-translational modifications. This results in the activation of the p53 protein as a transcription factor that initiates a program of cell cycle arrest, cellular senescence or apoptosis. The transcriptional network of p53-responsive genes produces proteins that interact with a large number of other signal transduction pathways in the cell and a number of positive and negative autoregulatory feedback loops act upon the p53 response. There are at least seven negative and three positive feedback loops described here, and of these, six act through the MDM-2 protein to regulate p53 activity. The p53 circuit communicates with the Wnt-beta-catenin, IGF-1-AKT, Rb-E2F, p38 MAP kinase, cyclin-cdk, p14/19 ARF pathways and the cyclin G-PP2A, and p73 gene products. There are at least three different ubiquitin ligases that can regulate p53 in an autoregulatory manner: MDM-2, Cop-1 and Pirh-2. The meaning of this redundancy and the relative activity of each of these feedback loops in different cell types or stages of development remains to be elucidated. The interconnections between signal transduction pathways will play a central role in our understanding of cancer.

Amino Acid Sequence↗
PubMed2003

Genomic instability and endoreduplication triggered by RAD17 deletion.

Cell cycle checkpoints are critical for genomic stability. Rad17, a component of the checkpoint clamp loader complex (Rad17/Rfc2-5), is required for the response to DNA damage and replication stress. To explore the role of Rad17 in the maintenance of genomic integrity, we established somatic conditional alleles of RAD17 in human cells. We find that RAD17 is not only important for the Atr-mediated checkpoint but is also essential for cell viability. Cells lacking RAD17 exhibited acute chromosomal aberrations and underwent endoreduplication at a high rate. Therefore, RAD17 links the checkpoint to ploidy control and is essential for the maintenance of chromosomal stability.

Blotting, Southern↗
PubMed2001

A novel copper-regulated promoter system for expression of heterologous proteins in Schizosaccharomyces pombe.

The increasing use of the fission yeast Schizosaccharomyces pombe as a model organism for elucidating the mechanisms of critical biological processes such as cell-cycle control, DNA replication, and stress-mediated signal transduction has fostered the development and utilization of expression systems for gene function analysis. Using the promoter of the ctr4(+) copper transporter gene from S. pombe, we created a series of vectors, named pctr4(+)-X, which regulate the expression of heterologous genes as a function of copper availability. In this system, the addition of copper ions at levels that are non-toxic to yeast cells represses gene expression, while copper deprivation strongly induces gene expression. Conveniently, changes of growth medium or carbon sources are not required to shut down or induce gene expression. The Cu-starvation-mediated inducible expression system is rapid, producing heterologous proteins within 3 h, with sustained expression of proteins that persists for several hours. The pctr4(+)-X expression vectors harbor unique restriction sites constructed in-frame to DNA sequences encoding for epitope tags, which facilitate the detection or purification of the heterologous proteins using commercially available antibodies and affinity columns. Furthermore, the pctr4(+)-X copper-regulatable protein expression vectors have been constructed with three different selectable markers, offering more versatility for studying gene function in fission yeast.

Cation Transport Proteins↗
PubMed2001

p53-dependent induction of p21(Cip1/WAF1/Sdi1) protects against oxygen-induced toxicity.

The beneficial effects of supplemental oxygen delivered to patients suffering from acute respiratory distress is offset by its reduction to genotoxic reactive oxygen species (ROS) that inhibit proliferation and kill pulmonary cells. Cells respond to oxygen-induced damage by expressing the tumor suppressor p53 and the cyclin-dependent kinase inhibitor p21(Cip1/WAF1/Sdi1) (p21), which limits proliferation by blocking entry into S phase. Since preventing DNA synthesis during genotoxic stress may enhance survival, the current study examines whether hyperoxia induces p21 through a p53-dependent pathway and whether p21 protects cells from the toxic effects of oxygen. HCT116 colon carcinoma cells and clonal lines lacking p53 or p21were used in this study because they allow direct cytotoxic comparisons between isogenic cells, without complications arising from unknown genetic differences between nonhomologous cell lines. Hyperoxia (95% O2, 5% CO2) increased p53 abundance, phosphorylation of p53 on serine 15, and p21 mRNA and protein in parental HCT116 cells that ceased proliferation. In contrast, p21 was not detected in either p53- or p21-deficient HCT116 cells, which exited the G1 compartment and were arrested in S and G2/M phases during hyperoxia. Trypan blue-dye exclusion revealed that induction of p21 markedly enhanced survival during exposure and colony survival assays showed that p21 enhanced the ability to resume proliferation during recovery in room air. The observation that p53-dependent induction of p21 prevents exit from G1 and promotes survival during hyperoxia is consistent with the importance of limiting DNA replication during genotoxic stress caused by oxygen exposure.

Blotting, Western↗
PubMed2005

Conditional inactivation of the mouse Hus1 cell cycle checkpoint gene.

The Hus1 cell cycle checkpoint protein plays a central role in genome maintenance by mediating cellular responses to DNA damage and replication stress. Targeted deletion of mouse Hus1 results in spontaneous chromosomal abnormalities and embryonic lethality. To study the physiological impact of Hus1 deficiency in adult mice, we generated a conditional Hus1 allele, Hus1(flox), in which exons two and three are flanked by loxP sites. Cre-mediated excision of the loxP-flanked region produces Hus1(Delta2,3), which is capable of encoding only 19 of 281 Hus1 amino acids. Germline homozygosity for Hus1(Delta2,3) resulted in mid-gestational embryonic lethality that was indistinguishable from that caused by an established null allele, Hus1(Delta1n). Hus1 was inactivated in adult mice using a transgenic strain in which Cre is sporadically expressed in a variety of tissues from the Hsp70-1 promoter. Conditional Hus1 knockout mice were produced at unexpectedly low frequency and, unlike control animals, demonstrated limited inactivation of the conditional allele, suggesting that Hus1-deficient cells were at a strong selective disadvantage in adult animals. However, viable conditional Hus1 knockout mice consistently showed the greatest degree of Hus1 inactivation specifically in lung and mammary gland, highlighting varying requirements for Hus1 in different tissues. The novel tools described here hold promise for elucidating how the Hus1-dependent checkpoint mechanism contributes to chromosomal stability, DNA damage responses, and tumor suppression in adult mice.

Alleles↗
PubMed2004

ATR functions as a gene dosage-dependent tumor suppressor on a mismatch repair-deficient background.

The ataxia-telangiectasia mutated and rad3-related (ATR) kinase orchestrates cellular responses to DNA damage and replication stress. Complete loss of ATR function leads to chromosomal instability and cell death. However, heterozygous ATR mutations are found in human cancers with microsatellite instability, suggesting that ATR haploinsufficiency contributes to tumorigenesis. To test this possibility, we generated human cell line and mouse model systems in which a single ATR allele was inactivated on a mismatch repair (MMR)-deficient background. Monoallelic ATR gene targeting in MLH1-deficient HCT 116 colon carcinoma cells resulted in hypersensitivity to genotoxic stress accompanied by dramatic increases in fragile site instability, and chromosomal amplifications and rearrangements. The ATR(+/-) HCT 116 cells also displayed compromised activation of Chk1, an important downstream target for ATR. In complementary studies, we demonstrated that mice bearing the same Atr(+/-)/Mlh1(-/-) genotype were highly prone to both embryonic lethality and early tumor development. These results demonstrate that MMR proteins and ATR functionally interact during the cellular response to genotoxic stress, and that ATR serves as a haploinsufficient tumor suppressor in MMR-deficient cells.

Adaptor Proteins, Signal Transducing↗
PubMed2006

The gene expression program of prostate fibroblast senescence modulates neoplastic epithelial cell proliferation through paracrine mechanisms.

The greatest risk factor for developing carcinoma of the prostate is advanced age. Potential molecular and physiologic contributors to the frequency of cancer occurrence in older individuals include the accumulation of somatic mutations through defects in genome maintenance, epigenetic gene silencing, oxidative stress, loss of immune surveillance, telomere dysfunction, chronic inflammation, and alterations in tissue microenvironment. In this context, the process of prostate carcinogenesis can be influenced through interactions between intrinsic cellular alterations and the extrinsic microenvironment and macroenvironment, both of which change substantially as a consequence of aging. In this study, we sought to characterize the molecular alterations that occur during the process of prostate fibroblast senescence to identify factors in the aged tissue microenvironment capable of promoting the proliferation and potentially the neoplastic progression of prostate epithelium. We evaluated three mechanisms leading to cell senescence: oxidative stress, DNA damage, and replicative exhaustion. We identified a consistent program of gene expression that includes a subset of paracrine factors capable of influencing adjacent prostate epithelial growth. Both direct coculture and conditioned medium from senescent prostate fibroblasts stimulated epithelial cell proliferation, 3-fold and 2-fold, respectively. The paracrine-acting proteins fibroblast growth factor 7, hepatocyte growth factor, and amphiregulin (AREG) were elevated in the extracellular environment of senescent prostate fibroblasts. Exogenous AREG alone stimulated prostate epithelial cell growth, and neutralizing antibodies and small interfering RNA targeting AREG attenuated, but did not completely abrogate the growth-promoting effects of senescent fibroblast conditioned medium. These results support the concept that aging-related changes in the prostate microenvironment may contribute to the progression of prostate neoplasia.

Cell Proliferation↗
PubMed2006

AIB1 promotes DNA replication by JNK repression and AKT activation during cellular stress.

Amplified in breast cancer 1 (AIB1) is a member of the p160 family of nuclear receptor coactivator protein. Recent studies have reported that high-level AIB1 production is involved in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway for progression to malignant carcinoma in a steroid-independent manner. Here we demonstrate that, in AIB1-knockout DT40 chicken B-lymphocytes, loss of AIB1 results in induction of phosphorylation of c-Jun N-terminal kinase (JNK) and c-Jun, in addition to the inhibition of DNA replication. In contrast, high-level AIB1 production prevents proapoptotic activation of the JNK/c-Jun signal transduction pathway and induces DNA replication through phosphorylation of the Akt/p65 NF-kappaB subunit RelA under cellular stresses such as UV irradiation or serum deprivation. Moreover, we have found that AIB1 is essential for the phosphorylation of histone H3 at serine 10, which is associated with the signal transduction to chromatin, leading to the transient expression of immediate-early genes in response to UV stimulation. Our results therefore suggest that AIB1 directly links to cell cycle control mechanisms in concern with the balance between apoptosis and proliferation.

Animals↗
PubMed2005

Human DNA topoisomerase I: relaxation, roles, and damage control.

Human DNA topoisomerase I is an essential enzyme involved in resolving the torsional stress associated with DNA replication, transcription, and chromatin condensation. The catalytic cycle of the enzyme consists of DNA cleavage to form a covalent enzyme-DNA intermediate, DNA relaxation, and finally, re-ligation of the phosphate backbone to restore the continuity of the DNA. Structure/function studies have elucidated a flexible enzyme that relaxes DNA through coordinated, controlled movements of distinct enzyme domains. The cellular roles of topoisomerase I are apparent throughout the nucleus, but the concentration of processes acting on ribosomal DNA results in topoisomerase I accumulation in the nucleolus. Although the activity of topoisomerase I is required in these processes, the enzyme can also have a deleterious effect on cells. In the event that the final re-ligation step of the reaction cycle is prevented, the covalent topoisomerase I-DNA intermediate becomes a toxic DNA lesion that must be repaired. The complexities of the relaxation reaction, the cellular roles, and the pathways that must exist to repair topoisomerase I-mediated DNA damage highlight the importance of continued study of this essential enzyme.

DNA Damage↗
PubMed2005

The DNA damage pathway regulates innate immune system ligands of the NKG2D receptor.

Some stimulatory receptors of the innate immune system, such as the NKG2D receptor (also called KLRK1) expressed by natural killer cells and activated CD8(+)T cells, recognize self-molecules that are upregulated in diseased cells by poorly understood mechanisms. Here we show that mouse and human NKG2D ligands are upregulated in non-tumour cell lines by genotoxic stress and stalled DNA replication, conditions known to activate a major DNA damage checkpoint pathway initiated by ATM (ataxia telangiectasia, mutated) or ATR (ATM- and Rad3-related) protein kinases. Ligand upregulation was prevented by pharmacological or genetic inhibition of ATR, ATM or Chk1 (a downstream transducer kinase in the pathway). Furthermore, constitutive ligand expression by a tumour cell line was inhibited by targeting short interfering RNA to ATM, suggesting that ligand expression in established tumour cells, which often harbour genomic irregularities, may be due to chronic activation of the DNA damage response pathway. Thus, the DNA damage response, previously shown to arrest the cell cycle and enhance DNA repair functions, or to trigger apoptosis, may also participate in alerting the immune system to the presence of potentially dangerous cells.

Animals↗
PubMed2004

Role of peroxisome proliferator-activated receptor-alpha (PPARalpha) in bezafibrate-induced hepatocarcinogenesis and cholestasis.

Prolonged administration of peroxisome proliferators to rodents typically leads to hepatocarcinogenesis. Peroxisome proliferator-activated receptor-alpha (PPARalpha) is required to mediate alterations in PPARalpha target gene expression, repress apoptosis, enhance replicative DNA synthesis, oxidative stress to DNA and hepatocarcinogenesis induced by the relatively specific PPARalpha agonist, Wy-14,643. Interestingly, administration of the less specific PPARalpha agonist, bezafibrate, leads to a modest induction of PPARalpha target genes in the absence of PPARalpha expression. In these studies, the role of PPARalpha in modulating hepatocarcinogenesis induced by long-term feeding of 0.5% bezafibrate was examined in wild-type (+/+) and PPARalpha-null (-/-) mice. The average liver weight was significantly higher in (+/+) and (-/-) mice fed bezafibrate than controls, but this effect was considerably less in (-/-) mice as compared with similarly treated (+/+) mice. Increased levels of mRNA encoding cell cycle regulatory proteins and DNA repair enzymes were found in (+/+) mice fed bezafibrate, and this effect was not found in (-/-) mice. In mice fed bezafibrate for 1 year, preneoplastic foci, adenomas and a hepatocellular carcinoma were found in (+/+) mice, while only a single microscopic adenoma was found in one (-/-) mouse. This effect was observed in both Sv/129 and C57BL/6N strains of mice, although only preneoplastic foci were observed in the latter strain. Interestingly, hepatic cholestasis was observed in 100% of the bezafibrate-fed (-/-) mice, and this was accompanied by significantly elevated hepatic expression of mRNA encoding bile salt export pump and lower expression of mRNA encoding cytochrome P450 7A1, consistent with enhanced activation of the bile acid receptor, farnesoid X receptor. Results from these studies demonstrate that the PPARalpha is required to mediate hepatocarcinogenesis induced by bezafibrate, and that PPARalpha protects against potential cholestasis.

Acyl-CoA Oxidase↗
PubMed2005

Genomic instability in radial growth phase melanoma cell lines after ultraviolet irradiation.

BACKGROUND/AIMS: Although ultraviolet (UV) irradiation, apoptosis, and genomic instability are all potentially involved in the pathogenesis of melanoma, in vitro studies investigating these changes in the radial growth phase of this neoplasm are still lacking; therefore, this study was designed to investigate these changes. METHOD: An in vitro system consisting of three radial growth phase Wistar melanoma cell lines (WM35, WM3211, and WM1650) was established. Cells were UV irradiated (10 mJ/cm2 for UVB and 6 J/cm2 for UVA), harvested after UV exposure, and evaluated for viability and apoptosis using Trypan blue and terminal deoxynucleotidyl transferase mediated dUTP digoxigenin nick end labelling assays, respectively. Polymerase chain reaction based microsatellite assays were used to examine the cell lines for the presence of microsatellite instability (MSI) using 21 markers at the 1p, 2p, 3p, 4q, 9p, and 17p regions. RESULTS: Exposure to UV initiated progressive cell death associated with pronounced apoptosis, with UVA having a greater effect than UVB. MSI was found in UVB (WM35 and WM3211) and UVA (WM35) irradiated cell lines at 1p, 9p, and 17p, but not in non-irradiated cells. The prevalence of MSI was higher after UVB irradiation (14%) than UVA irradiation (4.7%), and was most frequently found at D1S233. CONCLUSIONS: The ability of erythemogenic UV irradiation to induce both apoptosis and MSI in radial growth phase melanoma cells is suggestive of its role in melanoma pathogenesis. This instability may reflect a hypermutability state, oxidative stress induced DNA damage, replication infidelity, or a combination of these factors.

Apoptosis↗
PubMed2006

The DNA damage response arouses the immune system.

Although there is considerable knowledge of how DNA damage triggers cell cycle arrest, DNA repair, and apoptosis, little was known about its potential role in immune responses. Recently, we showed that genotoxic stress and stalled DNA replication forks induce the expression of ligands for the NKG2D receptor found in natural killer cells and certain T cells, cell types that are able to attack tumor cells. Chronic activation of this response in tumor cells may contribute to immune recognition, but it also imposes a selection mechanism for immune escape and malignant progression. This unique arm of the DNA damage response may have implications for understanding therapeutic responses, many of which induce the DNA damage response, and for designing more effective regimens to treat cancer.

Animals↗
PubMed2026

Dynamic and Ongoing De Novo L1 Retrotransposition Contributes to Genome Plasticity and Intrapatient Heterogeneity in Ovarian Cancer.

UNLABELLED: Long interspersed element-1 (L1) retrotransposons are the only protein-coding active transposable elements in the human genome. Although typically silenced in normal cells, they are highly expressed in many human epithelial cancers, including high-grade serous ovarian cancer (HGSC), and can integrate into the genome through retrotransposition. De novo L1 insertions are known to contribute to genomic instability and cancer evolution in epithelial malignancies, including HGSC, suggesting that they might also play a role in intrapatient tumor heterogeneity. In this study, we quantified de novo L1 insertions in clinical HGSC specimens and uncovered high heterogeneity in total L1 insertion events (L1 burden) between patients. HGSC tumors with high L1 burden were highly proliferative, whereas tumors with low or no L1 insertions showed enrichment of immune response and cell death pathways. Although the overall L1 burden was similar across different tumor sites within the same patient, the specific L1 insertions (L1 profiles) diverged significantly more than their single-nucleotide variants profiles. Taken together, these findings demonstrate that L1 activity and retrotransposition are highly dynamic in vivo and can contribute substantially to tumor genome plasticity, especially at late stages of cancer progression. The patient-specific propensity of acquiring L1 insertions (L1 burden) could be driven by molecular properties of the progenitor tumor. Retrotransposition-associated DNA damage and/or replication stress could be a potential molecular vulnerability for precision cancer medicine approaches. SIGNIFICANCE: L1 retrotransposition is a dynamic process that continues at late stages of high-grade serous ovarian cancer and can substantially contribute to intrapatient tumor heterogeneity.

Humans↗
PubMed2026

Ribonucleotide Reductase Inhibition Triggers Ferroptosis in Genetically Defined Subsets of Non-Small Cell Lung Cancer.

UNLABELLED: Non-small cell lung cancer (NSCLC) is responsible for the majority of cancer-related mortality worldwide. Lung adenocarcinoma is the most common NSCLC subtype. Despite advances in targeted therapies, treatment resistance remains a critical challenge. Ribonucleotide reductase (RNR), a crucial enzyme in deoxyribonucleotide triphosphate biosynthesis, is frequently upregulated in cancer, contributing to genomic instability and poor prognosis in multiple malignancies. However, the role of the RNR complex in driving tumorigenesis is not fully understood in oncogene-driven lung adenocarcinoma. Transcriptomic analysis of more than 27,000 real-world samples of patients with NSCLC revealed that RNR subunits (RRM1 and RRM2) are significantly upregulated in TP53-mutated NSCLC and are correlated with significantly poor prognosis in multiple oncogene-driven lung adenocarcinoma. Using pharmacologic and genetic approaches to inhibit RNR in lung adenocarcinoma models, we assessed functional consequences through molecular, biochemical, and imaging techniques. RNR inhibition induced appreciable replication stress and triggered DNA damage, leading to cell death in lung adenocarcinoma cells. Notably, we uncovered that RNR suppression preferentially induced ferroptosis, an iron-dependent cell death driven by lipid peroxidation. This represents a previously unrecognized mechanism of RNR-mediated cell death by which mutant lung adenocarcinoma cells can be selectively targeted. Our study establishes RNR inhibition as a potent strategy to selectively induce ferroptosis in oncogene-addicted lung adenocarcinoma, offering a new therapeutic avenue for genetically defined patient subgroups. Targeting nucleotide metabolism could serve as an effective approach to overcome treatment resistance and improve clinical outcomes for patients with high-risk lung adenocarcinoma. SIGNIFICANCE: Our findings highlight RNR as a promising therapeutic target in oncogene-driven lung adenocarcinoma. By demonstrating that RNR inhibition induces ferroptosis, our study opens up new possibilities for developing targeted therapies that selectively eliminate cancer cells in lung adenocarcinoma, paving the way for personalized treatment strategies and potentially overcoming resistance to current therapies.

Humans↗
PubMed2026

STN1 upregulation promotes PARPi resistance in BRCA2-deficient cancer cells via replication fork protection and suppression of ssDNA gap formation.

PARPi are effective therapy for BRCA1/2 mutant cancers, yet recurrent PARPi resistance frequently develops. The underlying mechanism of PARPi resistance remains largely unresolved. Here, we identify STN1, a component of the CTC1/STN1/TEN1 (CST) complex, as a modulator of PARPi resistance in BRCA2-deficient cells. RNA-seq analysis of PARPi-resistant cancer cells from BRCA2-mutated backgrounds shows largely distinct transcriptomic profiles with limited overlap, suggesting multiple routes to resistance. Notably, STN1 is consistently upregulated in resistant cells. We observe that overexpression of STN1 enhances Olaparib resistance in multiple BRCA2-deficient cell lines and alleviates DNA damage under replication stress. Mechanistically, we find that STN1 overexpression increases RAD51 loading to stalled replication forks while restricting MRE11 recruitment in BRCA2-deficient cells, thereby protecting stalled forks from nascent-strand degradation. Furthermore, STN1 overexpression rescues the accumulation of ssDNA gaps, a major determinant of PARPi sensitivity in BRCA2-deficient cells. Taken together, these findings suggest that elevated STN1 levels can partially compensate for BRCA2 loss by stabilizing stalled replication forks and limiting ssDNA gap accumulation. Our study uncovers a STN1-dependent pathway of replication stress tolerance that promotes PARPi resistance independently of homologous recombination restoration, highlighting STN1 as a potential biomarker and mechanistic contributor to therapeutic resistance in BRCA2-mutated cancers.

PARPi resistance↗
PubMed2026

The role of CHAMP1 in chromatin-mediated DNA damage repair.

Defects in the replication stress response are major drivers of cancer development and present key targetable vulnerabilities that can be exploited for anti-cancer therapy. Recent studies have identified CHAMP1 as a novel DNA damage repair factor with roles in double-strand break repair and the replication stress response. Mutations in CHAMP1 are associated with the neurodevelopmental disorder CHAMP1 Syndrome. More recently, children with CHAMP1 Syndrome have developed leukemia, suggesting that CHAMP1 mutations are a potential cancer risk factor. CHAMP1 is part of two DNA damage repair complexes: CHAMP1-POGZ-REV7 (Complex I) and CHAMP1-POGZ-HP1α (Complex II). Complex I promotes homologous recombination by removing the Shieldin complex from the ends of double strand breaks and allowing DSB end resection to occur. Complex II enriches heterochromatin content through the recruitment of the methyltransferase SETDB1 to DNA damage sites. Increased heterochromatin at stalled forks is associated with proper fork stability and restart, demonstrating the importance of CHAMP1 in maintaining genomic integrity. Loss of CHAMP1 leads to increased sensitivity to DNA damaging agents and increased dependence on other DNA damage repair pathways, such as the DNA damage checkpoint and the Fanconi Anemia pathway. CHAMP1 is overexpressed in breast and ovarian cancer cells with high levels of replication stress, providing a molecular mechanism for the tolerance of replication stress. These new findings on the relationship of CHAMP1 with well-established DNA damage repair pathways, suggest that targeting CHAMP1 could present a new synthetic lethality opportunity for cancer cells with high levels of replication stress.

CHAMP1↗
PubMed2024

Transient Zn2+ deficiency induces replication stress and compromises daughter cell proliferation.

Cells must replicate their genome quickly and accurately, and they require metabolites and cofactors to do so. Ionic zinc (Zn2+) is an essential micronutrient that is required for hundreds of cellular processes, including DNA synthesis and adequate proliferation. Deficiency in this micronutrient impairs DNA synthesis and inhibits proliferation, but the mechanism is unknown. Using fluorescent reporters to track single cells via long-term live-cell imaging, we find that Zn2+ is required at the G1/S transition and during S phase for timely completion of S phase. A short pulse of Zn2+ deficiency impairs DNA synthesis and increases markers of replication stress. These markers of replication stress are reversed upon resupply of Zn2+. Finally, we find that if Zn2+ is chelated during the mother cell's S phase, daughter cells enter a transient quiescent state, maintained by sustained expression of p21, which disappears upon reentry into the cell cycle. In summary, short pulses of mild Zn2+ deficiency in S phase specifically induce replication stress, which causes downstream proliferation impairments in daughter cells.

Zinc↗