Showing papers by "Ahmad Besaratinia published in 2010"
TL;DR: It is demonstrated that transcription-coupled nucleotide excision repair (TC-NER) provides protection against both classes of transcription-associated mutagenesis, and the existence of two mutagenic pathways operating specifically at the transcribed DNA strand of active genes is unveiled.
43 citations
TL;DR: Applications of the Hupki mouse model system for investigating mutagenesis induced by a variety of environmental carcinogens, including sunlight ultraviolet radiation, benzo [a] pyrene (a tobacco smoke‐derived carcinogen), 3‐nitrobenzanthrone (an urban air pollutant), aristolochic acid (a component of Chinese herbal medicine), and aflatoxin B1 (a food contaminant) are highlighted.
Abstract: Tumor-driving mutations in the TP53 gene occur frequently in human cancers. These inactivating mutations arise predominantly from a single-point mutation in the DNA-binding domain of this tumor suppressor gene (i.e., exons 4–9). The human p53 knock-in (Hupki) mouse model was constructed using gene-targeting technology to create a mouse strain that harbors human wild-type TP53 DNA sequences in both copies of the mouse TP53 gene. Replacement of exons 4–9 of the endogenous mouse TP53 alleles in the Hupki mouse with the homologous normal human TP53 gene sequences has offered a humanized replica of the TP53 gene in a murine genetic environment. The Hupki mouse model system has proven to be an invaluable research tool for studying the underlying mechanisms of human TP53 mutagenesis. The utility of the Hupki mouse model system for exploring carcinogen-induced TP53 mutagenesis has been demonstrated in both in vivo animal experiments and in vitro cell culture experiments. Here, we highlight applications of the Hupki mouse model system for investigating mutagenesis induced by a variety of environmental carcinogens, including sunlight ultraviolet radiation, benzo[a]pyrene (a tobacco smoke-derived carcinogen), 3-nitrobenzanthrone (an urban air pollutant), aristolochic acid (a component of Chinese herbal medicine), and aflatoxin B1 (a food contaminant). We summarize the salient findings of the respective studies and discuss their relevance to human cancer etiology.—Besaratinia, A., Pfeifer, G. P. Applications of the human p53 knock-in (Hupki) mouse model for human carcinogen testing.
29 citations
TL;DR: The absence of aberrant DNA methylation in the model system within a timeframe that precedes cellular transformation suggests that following carcinogen exposure, other as yet unknown factors may help initiate global loss of DNA methylisation and region-specific gain of DNAmethylation, which can, in turn, contribute to lung cancer development.
Abstract: Global loss of DNA methylation and locus/gene-specific gain of DNA methylation are two distinct hallmarks of carcinogenesis. Aberrant DNA methylation is implicated in smoking-related lung cancer. In this study, we have comprehensively investigated the modulation of DNA methylation consequent to chronic exposure to a prototype smoke-derived carcinogen, benzo[a]pyrene diol epoxide (B[a]PDE), in genomic regions of significance in lung cancer, in normal human cells. We have used a pulldown assay for enrichment of the CpG methylated fraction of cellular DNA combined with microarray platforms, followed by extensive validation through conventional bisulfite-based analysis. Here, we demonstrate strikingly similar patterns of DNA methylation in non-transformed B[a]PDE-treated cells vs control using high-throughput microarray-based DNA methylation profiling confirmed by conventional bisulfite-based DNA methylation analysis. The absence of aberrant DNA methylation in our model system within a timeframe that precedes cellular transformation suggests that following carcinogen exposure, other as yet unknown factors (secondary to carcinogen treatment) may help initiate global loss of DNA methylation and region-specific gain of DNA methylation, which can, in turn, contribute to lung cancer development. Unveiling the initiating events that cause aberrant DNA methylation in lung cancer has tremendous public health relevance, as it can help define future strategies for early detection and prevention of this highly lethal disease.
17 citations
TL;DR: Investigating the status of CpG methylation in the substituted segment of the Hupki mouse genome and comparing it to the methylation profile of the corresponding segment in the human genome found that all cytosines within CpGs of the TP53 DNA‐binding domain, on both the coding and noncoding strands, were heavily methylated in H upki fibroblasts, as they were in human fibro Blasts.
Abstract: Methylated cytosines within CpG dinucleotides (mCpGs) along the DNA-binding domain of the TP53 tumor suppressor gene (exons ∼5–8) are the single most significant mutational target in human cancers. The human p53 knock-in (Hupki) mouse model was constructed using gene-targeting technology to create a mouse strain that harbors human wild-type TP53 DNA sequences spanning exons 4–9 in both copies of the mouse p53 gene. To date, however, the methylation status of cytosines within CpGs in the substituted segment of the Hupki mouse genome has not been determined. This lack of information deserves special attention because DNA methylation in mammals, which occurs almost exclusively within CpG dinucleotides, is a dynamic process throughout developmental stages and may vary among different species. Here, we have investigated the status of CpG methylation in the substituted segment of the Hupki mouse genome, and compared it to the methylation profile of the corresponding segment in the human genome using the combined bisulfite-restriction analysis and sodium bisulfite genomic sequencing. We found that all cytosines within CpGs of the TP53 DNA-binding domain, on both the coding and noncoding strands, were heavily methylated in Hupki fibroblasts, as they were in human fibroblasts. This is in keeping with the fully methylated status of TP53 CpGs that is known to prevail in adult human tissues. The remarkably similar patterns of cytosine methylation within CpG dinucleotides in Hupki cells and human cells further validates the suitability of mutagenesis assays in Hupki cells for experimental induction of TP53 mutations that have been observed in human tumors. © 2010 Wiley-Liss, Inc.
5 citations