Induction of T --> G and T --> A transversions by 5-formyluracil in mammalian cells.
Oxidatively damaged thymine, 5-formyluracil (5-fU), was incorporated into a predetermined site of double-stranded shuttle vectors. The nucleotide sequences in which the modified base was incorporated were 5'-CFTAAG-3' and 5'-CTFAAG-3' (F represents 5-fU), the recognition site for the restriction enzyme AflII (5'-CTTAAG-3'). The 5-fU was incorporated into a template strand of either the leading or lagging strand of DNA replication. The modified DNAs were transfected into simian COS-7 cells, and the DNAs replicated in the cells were recovered and were analyzed after the second transfection into Escherichia coli. The 5-fU did not block DNA replication in mammalian cells. The 5-fU residues were weakly mutagenic, and their mutation frequencies in double-stranded vectors were 0.01-0.04%. The T --> G and T --> A transversions were the mutations found most frequently, suggesting the formation of 5-fU.C and 5-fU.T base pairs, respectively. This is the first report that clearly shows the induction of transversion mutations by an oxidized pyrimidine base in DNA in mammalian cells.
Kamiya
Hiroyuki
H
Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan. hirokam@pharm.hokudai.ac.jp
Murata-Kamiya
Naoko
N
Karino
Naoko
N
Ueno
Yoshihito
Y
Matsuda
Akira
A
Kasai
Hiroshi
H
D000818:Animals; D019556:COS Cells; D008968:Molecular Conformation; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D014498:Uracil / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity*
D009153:Mutagens; C007777:5-formyluracil; D014498:Uracil