Mutation induced by deoxyxanthosine in codon 12 of a synthetic c-Ha-ras gene.

To evaluate the base-pairing properties and mutagenicity of deoxyxanthosine in DNA, the modified base was incorporated into a synthetic c-Ha-ras gene and a DNA transfection experiment was done. The ras gene containing deoxyxanthosine showed very high focus-forming activity. Analysis of the genes from transformants showed almost exclusively a transition of G to A. These results indicate that dTMP was preferentially incorporated at the site opposite to deoxyxanthosine, and deoxyxanthosine can induce G to A transitions in mammalian cells.