UV-induced base substitution mutations in a shuttle vector plasmid propagated in group C xeroderma pigmentosum cells.
To assess the contribution to mutagenesis of human DNA repair defects, the UV-irradiated shuttle vector plasmid pZ189 was propagated in fibroblasts derived from a xeroderma pigmentosum (XP) patient in DNA repair complementation group C. In comparison to results with DNA repair-proficient human cells (WI-38 VA13), UV-irradiated pZ189 propagated in the XP-C (XP4PA(SV)) cells showed fewer surviving plasmids and a higher frequency of mutated plasmids. Base sequence analysis of 67 mutated plasmids recovered from the XP-C cells revealed similar classes of point mutations and mutation spectrum, and a higher frequency of G:C to A:T transitions along with a lower frequency of transversions among plasmids with single or tandem mutations compared to plasmids recovered from the normal line. Most single-base substitution mutations (83%) occurred at G:C base pairs in which the 5'-adjacent base of the cytosine was thymine or cytosine. These results indicate that the DNA repair defects in XP-C, in comparison to data previously reported for XP-A, XP-D and XP-F, result in different UV survival and mutation frequency but in similar types of base substitution mutations.
Department of Experimental Radiology, Faculty of Medicine, Kyoto University, Japan.
T
T
Yagi
M
M
Sato
J
J
Tatsumi-Miyajima
H
H
Takebe
D001483:Base Sequence; D002460:Cell Line; D002461:Cell Line, Transformed; D004247:DNA; D004260:DNA Repair / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010957:Plasmids / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
D004247:DNA