Title: N-hydroxy-4-aminobiphenyl-DNA binding in human p53 gene: sequence preference and the effect of C5 cytosine methylation.
Authors: Feng, Zhaohui; Hu, Wenwei; Rom, William N; Beland, Frederick A; Tang, Moon-shong
Published In Biochemistry, (2002 May 21)
Abstract: 4-Aminobiphenyl (4-ABP) is a major etiological agent for human bladder cancer. Metabolically activated 4-ABP is able to interact with DNA to form adducts that may induce mutations and initiate carcinogenesis. Thirty to sixty percent of bladder cancer has a mutation in the tumor suppressor p53 gene, and the mutational spectrum bears unique features. To date the DNA binding spectrum of 4-ABP in the p53 gene is not known due to the lack of methodology to detect 4-ABP-DNA adducts at nucleotide sequence level. We have found that UvrABC nuclease, a nucleotide excision repair complex isolated from Escherichia coli, is able to incise specifically and quantitatively DNA fragments modified with N-hydroxy-4-aminobiphenyl (N-OH-4-ABP), an activated intermediate of 4-ABP. Using the UvrABC nuclease incision method, we mapped the binding spectrum of N-OH-4-ABP in DNA fragments containing exons 5, 7, and 8 of the human p53 gene and also determined the effect of C5 cytosine methylation on N-OH-4-ABP-DNA binding. We found that codon 285, a mutational hotspot at a non-CpG site in bladder cancer, is the preferential binding site for N-OH-4-ABP. We also found that C5 cytosine methylation greatly enhanced N-OH-4-ABP binding at CpG sites, and that two mutational hotspots at CpG sites, codons 175 and 248, became preferential binding sites for N-OH-4-ABP only after being methylated. These results suggest that both the unique DNA binding specificity of 4-ABP and cytosine methylation contribute to the mutational spectrum of the p53 gene in human bladder cancer.
PubMed ID: 12009904
MeSH Terms: Aminobiphenyl Compounds/chemistry; Aminobiphenyl Compounds/metabolism*; Base Sequence; Binding Sites/genetics; Carcinogens/chemistry; Carcinogens/metabolism*; CpG Islands; Cytosine/metabolism*; DNA Adducts/chemistry; DNA Adducts/metabolism*; DNA Damage; DNA Methylation*; Endodeoxyribonucleases/chemistry; Escherichia coli Proteins*; Exons/genetics; Genes, p53*/drug effects; Humans; Molecular Sequence Data; Mutagens/chemistry; Mutagens/metabolism*; Nucleic Acid Denaturation/drug effects; Urinary Bladder Neoplasms/etiology; Urinary Bladder Neoplasms/metabolism