Mutagenesis of codon 248 of the human p53 tumor suppressor gene by N-ethyl-N-nitrosourea.
Base pair mutations in the p53 tumor suppressor gene are among the most frequently observed genetic changes in human malignancies. Several mutational hotspots have been identified and tumor- and tissue-specific differences have been observed. We studied the mutability of hotspot codon 248, CGG, in human fibroblasts in response to the alkylating agent N-ethyl-N-nitrosourea (ENU) by MspI RFLP/PCR analysis. Alkylating agents are implicated as etiological agents in carcinogenesis in the gut and other tissues in the human. ENU induced preferentially G to A transitions in the non-transcribed strand. The predominant mutation involving the G-residue of the CpG dinucleotide was observed with an absolute frequency of 4 x 10(-7). The corresponding C to T transition in the first position of codon 248 was observed at several fold lower frequency suggesting more efficient excision repair of the transcribed strand. The G to A transition in the third position of codon 248 occurred at low frequency. Our results are compatible with a role for aliphatic alkylating agents in human tumors with codon 248 mutations since almost all mutations reported in this codon are transitions in the CpG-dinucleotide.
Hussain
S P
SP
Department of Carcinogenesis, Swiss Institute for Experimental Cancer Research, Epalinges, Lausanne.
Aguilar
F
F
Cerutti
P
P
D001483:Base Sequence; D002478:Cells, Cultured; D003062:Codon; D005038:Ethylnitrosourea / Q000633:toxicity*; D016158:Genes, p53 / Q000187:drug effects*; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
D003062:Codon; D005038:Ethylnitrosourea