Mechanisms of excision of 5-fluorouracil by uracil DNA glycosylase in normal human cells.
Recent evidence indicates that 5-fluorouracil (5-FlUra) is incorporated into DNA and is removed by the DNA repair enzyme uracil DNA glycosylase. Synthetic oligonucleotides containing either a single uracil or 5-FlUra residue were constructed to examine the mechanisms by which human cells remove 5-FlUra from DNA. The human uracil DNA glycosylase excised uracil in a manner similar to that observed for the bacterial enzyme. In contrast, a significant difference was observed in their abilities to remove 5-FlUra. In particular, both the bacterial and normal human enzymes displayed 13-17-fold increases in their apparent Km values but the apparent Vmax values remained virtually constant. These results demonstrate that normal human cells possess a defined capacity to remove 5-FlUra incorporated into DNA. However, specific kinetic differences may exist that affect their capacity to remove 5-FlUra formed in DNA after treatment with this cancer chemotherapeutic agent.
Mauro
D J
DJ
Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
De Riel
J K
JK
Tallarida
R J
RJ
Sirover
M A
MA
D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D045647:DNA Glycosylases; D004260:DNA Repair; D004926:Escherichia coli / Q000201:enzymology; D005472:Fluorouracil / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D051981:Uracil-DNA Glycosidase
D009838:Oligodeoxyribonucleotides; D004247:DNA; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D005472:Fluorouracil