Mutagenic effects of 5-formyluracil on a plasmid vector during replication in Escherichia coli.
OBJECTIVE
5-Formyluracil (5-foU) is a major derivative of thymine produced in DNA by ionizing radiation and various chemical oxidants. It has been previously shown that 5-foU in template DNA directs misincorporation of nucleotides by DNA polymerases during in vitro DNA synthesis. The present experiments were designed to understand the biological effects of5-foU in vivo.


METHODS
The modified base was incorporated site-specifically into the recognition site of restriction endonuclease SalI (5'-GTCGAC) or AflII (5'-CTTAAG) in vector plasmid pSVK3 and introduced the plasmid into Escherichia coli.


RESULTS
When the plasmids were replicated in E. coli, 5-foU caused mutations at the target sites. The induced mutation frequencies were 0.038-0.049%. Sequence analysis revealed that 5-foU preferentially caused T:A-->C:G and T:A-->A:T base substitutions and -1 deletions at the 5-foU site. 5-FoU also caused mutations at sites near the 5-foU. The alkA mutation did not affect the frequency of mutations in 5-foU-containing plasmids.


CONCLUSIONS
The present experiments demonstrated that 5-formyluracil in DNA caused mutations in E. coli.
Miyabe
I
I
Laboratory of Radiation Biology, Graduate School of Science, Kyoto University, Japan.
Zhang
Q M
QM
Sugiyama
H
H
Kino
K
K
Yonei
S
S
D004247:DNA / Q000187:drug effects*; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics; D010957:Plasmids / Q000378:metabolism*; D014498:Uracil / Q000009:adverse effects* / Q000031:analogs & derivatives* / Q000378:metabolism
C007777:5-formyluracil; D014498:Uracil; D004247:DNA; C023091:rubredoxin-NAD+ reductase; D009247:NADH, NADPH Oxidoreductases