Fanconi anemia cells have a normal gene structure for topoisomerase I.
Cells from Fanconi anemia (FA) patients have defective DNA repair and are hypersensitive to DNA crosslinking agents such as mitomycin C (MMC). We examined the possibility that topoisomerase I is involved in the DNA crosslink repair system and is deficient in FA group A cells. FA cells and control cells were exposed to MMC with or without camptothecin (CPT), a topoisomerase I inhibitor. The cells did not show any increased sensitivity to killing by MMC with CPT, suggesting that the topoisomerase I is not involved in MMC-damaged DNA repair. However, FA cells showed increased sensitivity to CPT in comparison to control cells, raising the possibility of altered topoisomerase I in FA cells. Therefore, a mutation analysis was performed on topoisomerase I cDNA from FA cells by using chemical cleavage mismatch scanning and nucleotide sequencing. No mutation was detected from GM1309, a group A FA cell line. A base transition (C to T) at position 241, causing an amino acid change (His to Tyr), was found in GM2061, a FA cell line of unknown complementation group. However, allele-specific oligonucleotide hybridization analysis showed that this is a gene polymorphism. We conclude that FA cells have normal gene structure for topoisomerase I.
Saito
H
H
Department of Molecular and Medical Genetics, Oregon Health Sciences University, Portland 97201.
Grompe
M
M
Neeley
T L
TL
Jakobs
P M
PM
Moses
R E
RE
D001483:Base Sequence; D002166:Camptothecin / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004252:DNA Mutational Analysis; D017931:DNA Primers; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D005199:Fanconi Anemia / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction
D017931:DNA Primers; D016685:Mitomycin; D004247:DNA; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin