Edwin Zwart - Academia.edu (original) (raw)
Papers by Edwin Zwart
Molecular and Cellular Biology, Mar 1, 2008
Phosphorylation is important in p53-mediated DNA damage responses. After UV irradiation, p53 is p... more Phosphorylation is important in p53-mediated DNA damage responses. After UV irradiation, p53 is phosphorylated specifically at murine residue Ser389. Phosphorylation mutant p53.S389A cells and mice show reduced apoptosis and compromised tumor suppression after UV irradiation. We investigated the underlying cellular processes by time-series analysis of UV-induced gene expression responses in wild-type, p53.S389A, and p53 ؊/؊ mouse embryonic fibroblasts. The absence of p53.S389 phosphorylation already causes small endogenous gene expression changes for 2,253, mostly p53-dependent, genes. These genes showed basal gene expression levels intermediate to the wild type and p53 ؊/؊ , possibly to readjust the p53 network. Overall, the p53.S389A mutation lifts p53-dependent gene repression to a level similar to that of p53 ؊/؊ but has lesser effect on p53-dependently induced genes. In the wild type, the response of 6,058 genes to UV irradiation was strictly biphasic. The early stress response, from 0 to 3 h, results in the activation of processes to prevent the accumulation of DNA damage in cells, whereas the late response, from 12 to 24 h, relates more to reentering the cell cycle. Although the p53.S389A UV gene response was only subtly changed, many cellular processes were significantly affected. The early response was affected the most, and many cellular processes were phasespecifically lost, gained, or altered, e.g., induction of apoptosis, cell division, and DNA repair, respectively. Altogether, p53.S389 phosphorylation seems essential for many p53 target genes and p53-dependent processes.
Oncogene, Dec 13, 2010
The p53 gene is frequently mutated in cancers and it is vital for cell cycle control, homeostasis... more The p53 gene is frequently mutated in cancers and it is vital for cell cycle control, homeostasis and carcinogenesis. We describe a novel p53 mutational spectrum, different to those generally observed in human and murine tumors. Our study shows a high prevalence of nonsense mutations in the p53 N terminus of 2-acetylaminofluorene (2-AAF)-induced urinary bladder tumors. These nonsense mutations forced downstream translation initiation at codon 41 of Trp53, resulting in the aberrant expression of the p53 isoform DN-p53 (or p44). We propose a novel mechanism for the origination and the selection for this isoform. We show that chemical exposure can act as a novel cause of selection for this truncated protein. In addition, our data suggest that the occurrence of DN-p53 accounts, at least in mice, for a cancer phenotype. We also show that gene expression profiles of embryonic stem (ES) cells carrying the DN-p53 isoform in a p53-null background are divergent from p53 knockout ES cells, and therefore postulate that DN-p53 itself has functional transcriptional properties.
Mutation Research: Fundamental And Molecular Mechanisms Of Mutagenesis, Sep 1, 1997
Toxicological Sciences, Oct 20, 2010
Legends to supplemental Figures Supplemental Figure 3. Histopathological features of carcinogen-i... more Legends to supplemental Figures Supplemental Figure 3. Histopathological features of carcinogen-induced tumors of p53.S389A mice A. 2-AAF-induced transitional cell papilloma showing exophytic pattern of growth, well differentiated epithelium and no invasion. B. 2-AAF-induced carcinoma in situ showing pleomorphic and atypical epithelial cells from basal layer up to surface. Invasion of
Oncogene, Sep 13, 2004
Mdm2 and its homolog Mdm4 inhibit the function of the tumor suppressor p53. Targeted disruption o... more Mdm2 and its homolog Mdm4 inhibit the function of the tumor suppressor p53. Targeted disruption of either mdm2 or mdm4 genes in mice results in embryonic lethality that is completely rescued by concomitant deletion of p53, suggesting that deletion of negative regulators of p53 results in a constitutively active p53. Thus, these mouse models offer a unique in vivo system to assay the functional significance of different p53 modifications. Phosphorylation of serine 389 in murine p53 occurs specifically after ultraviolet-light-induced DNA damage, and phosphorylation of this site enhances p53 activity both in vitro and in vivo. Recently, mice with a serine to alanine substitution at serine 389 (p53 S389A) in the endogenous p53 locus were generated. To examine the in vivo significance of serine 389 phosphorylation during embryogenesis, we crossed these mutant mice to mice lacking mdm2 or mdm4. The p53 S389A allele did not alter the embryonic lethality of mdm2 or mdm4. Additional crosses to assay the effect of one p53 S389A allele with a p53 null allele also did not rescue the lethal phenotypes. In conclusion, the phenotypes due to loss of mdm2 or mdm4 were not even partially rescued by p53 S389A , suggesting that p53 S389A is functionally wild type during embryogenesis.
International Journal of Molecular Sciences, Feb 10, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Supplementary Figure S5 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Ace... more Supplementary Figure S5 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Figure Legends from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop ... more Supplementary Figure Legends from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Table S3 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acet... more Supplementary Table S3 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Figure S4 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Ace... more Supplementary Figure S4 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Environmental Health Perspectives
Background: Humans are exposed to combinations of chemicals. In cumulative risk assessment (CRA),... more Background: Humans are exposed to combinations of chemicals. In cumulative risk assessment (CRA), regulatory bodies such as the European Food Safety Authority consider dose addition as a default and sufficiently conservative approach. The principle of dose addition was confirmed previously for inducing craniofacial malformations in zebrafish embryos in binary mixtures of chemicals with either similar or dissimilar modes of action (MOAs). Objectives: In this study, we explored a workflow to select and experimentally test multiple compounds as a complex mixture with each of the compounds at or below its no observed adverse effect level (NOAEL), in the same zebrafish embryo model. Methods: Selection of candidate compounds that potentially induce craniofacial malformations was done using in silico methods—structural similarity, molecular docking, and quantitative structure–activity relationships—applied to a database of chemicals relevant for oral exposure in humans via food (EuroMix inventory, n=1,598). A final subselection was made manually to represent different regulatory fields (e.g., food additives, industrial chemicals, plant protection products), different chemical families, and different MOAs. Results: A final selection of eight compounds was examined in the zebrafish embryo model, and craniofacial malformations were observed in embryos exposed to each of the compounds, thus confirming the developmental toxicity as predicted by the in silico methods. When exposed to a mixture of the eight compounds, each at its NOAEL, substantial craniofacial malformations were observed; according to a dose–response analysis, even embryos exposed to a 7-fold dilution of this mixture still exhibited a slight abnormal phenotype. The cumulative effect of the compounds in the mixture was in accordance with dose addition (added doses of the individual compounds after adjustment for relative potencies), despite different MOAs of the compounds involved. Discussion: This case study of a complex mixture inducing craniofacial malformations in zebrafish embryos shows that dose addition can adequately predicted the cumulative effect of a mixture of multiple substances at low doses, irrespective of the (expected) MOA. The applied workflow may be useful as an approach for CRA in general. https://doi.org/10.1289/EHP9888
Toxicology and Applied Pharmacology, 2020
Conclusion: Overall, Our findings suggest that catechin hydrate inhibits B(a)P-induced lung tumor... more Conclusion: Overall, Our findings suggest that catechin hydrate inhibits B(a)P-induced lung tumor formation by modulating hyperproliferation, inflammation, apoptosis and ALDH1 expression.
Food and Chemical Toxicology, 2020
A challenge in cumulative risk assessment is to model hazard of mixtures. EFSA proposed to only c... more A challenge in cumulative risk assessment is to model hazard of mixtures. EFSA proposed to only combine chemicals linked to a defined endpoint, in so-called cumulative assessment groups, and use the dose-addition model as a default to predict combined effects. We investigated the effect of binary mixtures of compounds known to cause craniofacial malformations, by assessing the effect in the head skeleton (M-PQ angle) in 120hpf zebrafish embryos. We combined chemicals with similar mode of action (MOA), i.e. the triazoles cyproconazole, triadimefon and flusilazole; next, reference compounds cyproconazole or triadimefon were combined with dissimilar acting compounds, TCDD, thiram, VPA, prochloraz, fenpropimorph, PFOS, or endosulfan. These mixtures were designed as (near) equipotent combinations of the contributing compounds, in a range of cumulative concentrations. Dose-addition was assessed by evaluation of the overlap of responses of each of the 14 tested binary mixtures with those of the single compounds. All 10 test compounds induced an increase of the M-PQ angle, with varying potency and specificity. Mixture responses as predicted by dose-addition did not deviate from the observed responses, supporting dose-addition as a valid assumption for mixture risk assessment. Importantly, dose-addition was found irrespective of MOA of contributing chemicals.
Molecular and Cellular Biology, Mar 1, 2008
Phosphorylation is important in p53-mediated DNA damage responses. After UV irradiation, p53 is p... more Phosphorylation is important in p53-mediated DNA damage responses. After UV irradiation, p53 is phosphorylated specifically at murine residue Ser389. Phosphorylation mutant p53.S389A cells and mice show reduced apoptosis and compromised tumor suppression after UV irradiation. We investigated the underlying cellular processes by time-series analysis of UV-induced gene expression responses in wild-type, p53.S389A, and p53 ؊/؊ mouse embryonic fibroblasts. The absence of p53.S389 phosphorylation already causes small endogenous gene expression changes for 2,253, mostly p53-dependent, genes. These genes showed basal gene expression levels intermediate to the wild type and p53 ؊/؊ , possibly to readjust the p53 network. Overall, the p53.S389A mutation lifts p53-dependent gene repression to a level similar to that of p53 ؊/؊ but has lesser effect on p53-dependently induced genes. In the wild type, the response of 6,058 genes to UV irradiation was strictly biphasic. The early stress response, from 0 to 3 h, results in the activation of processes to prevent the accumulation of DNA damage in cells, whereas the late response, from 12 to 24 h, relates more to reentering the cell cycle. Although the p53.S389A UV gene response was only subtly changed, many cellular processes were significantly affected. The early response was affected the most, and many cellular processes were phasespecifically lost, gained, or altered, e.g., induction of apoptosis, cell division, and DNA repair, respectively. Altogether, p53.S389 phosphorylation seems essential for many p53 target genes and p53-dependent processes.
Oncogene, Dec 13, 2010
The p53 gene is frequently mutated in cancers and it is vital for cell cycle control, homeostasis... more The p53 gene is frequently mutated in cancers and it is vital for cell cycle control, homeostasis and carcinogenesis. We describe a novel p53 mutational spectrum, different to those generally observed in human and murine tumors. Our study shows a high prevalence of nonsense mutations in the p53 N terminus of 2-acetylaminofluorene (2-AAF)-induced urinary bladder tumors. These nonsense mutations forced downstream translation initiation at codon 41 of Trp53, resulting in the aberrant expression of the p53 isoform DN-p53 (or p44). We propose a novel mechanism for the origination and the selection for this isoform. We show that chemical exposure can act as a novel cause of selection for this truncated protein. In addition, our data suggest that the occurrence of DN-p53 accounts, at least in mice, for a cancer phenotype. We also show that gene expression profiles of embryonic stem (ES) cells carrying the DN-p53 isoform in a p53-null background are divergent from p53 knockout ES cells, and therefore postulate that DN-p53 itself has functional transcriptional properties.
Mutation Research: Fundamental And Molecular Mechanisms Of Mutagenesis, Sep 1, 1997
Toxicological Sciences, Oct 20, 2010
Legends to supplemental Figures Supplemental Figure 3. Histopathological features of carcinogen-i... more Legends to supplemental Figures Supplemental Figure 3. Histopathological features of carcinogen-induced tumors of p53.S389A mice A. 2-AAF-induced transitional cell papilloma showing exophytic pattern of growth, well differentiated epithelium and no invasion. B. 2-AAF-induced carcinoma in situ showing pleomorphic and atypical epithelial cells from basal layer up to surface. Invasion of
Oncogene, Sep 13, 2004
Mdm2 and its homolog Mdm4 inhibit the function of the tumor suppressor p53. Targeted disruption o... more Mdm2 and its homolog Mdm4 inhibit the function of the tumor suppressor p53. Targeted disruption of either mdm2 or mdm4 genes in mice results in embryonic lethality that is completely rescued by concomitant deletion of p53, suggesting that deletion of negative regulators of p53 results in a constitutively active p53. Thus, these mouse models offer a unique in vivo system to assay the functional significance of different p53 modifications. Phosphorylation of serine 389 in murine p53 occurs specifically after ultraviolet-light-induced DNA damage, and phosphorylation of this site enhances p53 activity both in vitro and in vivo. Recently, mice with a serine to alanine substitution at serine 389 (p53 S389A) in the endogenous p53 locus were generated. To examine the in vivo significance of serine 389 phosphorylation during embryogenesis, we crossed these mutant mice to mice lacking mdm2 or mdm4. The p53 S389A allele did not alter the embryonic lethality of mdm2 or mdm4. Additional crosses to assay the effect of one p53 S389A allele with a p53 null allele also did not rescue the lethal phenotypes. In conclusion, the phenotypes due to loss of mdm2 or mdm4 were not even partially rescued by p53 S389A , suggesting that p53 S389A is functionally wild type during embryogenesis.
International Journal of Molecular Sciences, Feb 10, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Supplementary Figure S5 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Ace... more Supplementary Figure S5 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Figure Legends from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop ... more Supplementary Figure Legends from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Table S3 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acet... more Supplementary Table S3 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Supplementary Figure S4 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Ace... more Supplementary Figure S4 from Lack of p53 Ser389 Phosphorylation Predisposes Mice to Develop 2-Acetylaminofluorene–Induced Bladder Tumors but not Ionizing Radiation–Induced Lymphomas
Environmental Health Perspectives
Background: Humans are exposed to combinations of chemicals. In cumulative risk assessment (CRA),... more Background: Humans are exposed to combinations of chemicals. In cumulative risk assessment (CRA), regulatory bodies such as the European Food Safety Authority consider dose addition as a default and sufficiently conservative approach. The principle of dose addition was confirmed previously for inducing craniofacial malformations in zebrafish embryos in binary mixtures of chemicals with either similar or dissimilar modes of action (MOAs). Objectives: In this study, we explored a workflow to select and experimentally test multiple compounds as a complex mixture with each of the compounds at or below its no observed adverse effect level (NOAEL), in the same zebrafish embryo model. Methods: Selection of candidate compounds that potentially induce craniofacial malformations was done using in silico methods—structural similarity, molecular docking, and quantitative structure–activity relationships—applied to a database of chemicals relevant for oral exposure in humans via food (EuroMix inventory, n=1,598). A final subselection was made manually to represent different regulatory fields (e.g., food additives, industrial chemicals, plant protection products), different chemical families, and different MOAs. Results: A final selection of eight compounds was examined in the zebrafish embryo model, and craniofacial malformations were observed in embryos exposed to each of the compounds, thus confirming the developmental toxicity as predicted by the in silico methods. When exposed to a mixture of the eight compounds, each at its NOAEL, substantial craniofacial malformations were observed; according to a dose–response analysis, even embryos exposed to a 7-fold dilution of this mixture still exhibited a slight abnormal phenotype. The cumulative effect of the compounds in the mixture was in accordance with dose addition (added doses of the individual compounds after adjustment for relative potencies), despite different MOAs of the compounds involved. Discussion: This case study of a complex mixture inducing craniofacial malformations in zebrafish embryos shows that dose addition can adequately predicted the cumulative effect of a mixture of multiple substances at low doses, irrespective of the (expected) MOA. The applied workflow may be useful as an approach for CRA in general. https://doi.org/10.1289/EHP9888
Toxicology and Applied Pharmacology, 2020
Conclusion: Overall, Our findings suggest that catechin hydrate inhibits B(a)P-induced lung tumor... more Conclusion: Overall, Our findings suggest that catechin hydrate inhibits B(a)P-induced lung tumor formation by modulating hyperproliferation, inflammation, apoptosis and ALDH1 expression.
Food and Chemical Toxicology, 2020
A challenge in cumulative risk assessment is to model hazard of mixtures. EFSA proposed to only c... more A challenge in cumulative risk assessment is to model hazard of mixtures. EFSA proposed to only combine chemicals linked to a defined endpoint, in so-called cumulative assessment groups, and use the dose-addition model as a default to predict combined effects. We investigated the effect of binary mixtures of compounds known to cause craniofacial malformations, by assessing the effect in the head skeleton (M-PQ angle) in 120hpf zebrafish embryos. We combined chemicals with similar mode of action (MOA), i.e. the triazoles cyproconazole, triadimefon and flusilazole; next, reference compounds cyproconazole or triadimefon were combined with dissimilar acting compounds, TCDD, thiram, VPA, prochloraz, fenpropimorph, PFOS, or endosulfan. These mixtures were designed as (near) equipotent combinations of the contributing compounds, in a range of cumulative concentrations. Dose-addition was assessed by evaluation of the overlap of responses of each of the 14 tested binary mixtures with those of the single compounds. All 10 test compounds induced an increase of the M-PQ angle, with varying potency and specificity. Mixture responses as predicted by dose-addition did not deviate from the observed responses, supporting dose-addition as a valid assumption for mixture risk assessment. Importantly, dose-addition was found irrespective of MOA of contributing chemicals.