High frequency and error-prone DNA recombination in ataxia telangiectasia cell lines.
The only specific DNA repair defect found in ataxia telangiectasia (A-T) cells is mis-repair of cleaved DNA. In this report we measured DNA recombination, given its role in DNA repair and genetic instability. Using plasmids containing selectable reporter genes, we found a higher frequency of both chromosomal recombination (>100 times) and extra-chromosomal recombination (27 times) in SV40-transformed A-T cell lines compared with in an SV40-transformed normal fibroblast cell line. Southern analysis of single A-T colonies exhibiting post-integration recombination revealed that 24/27 had undergone aberrant rearrangements; recombination in normal fibroblast colonies was achieved by gene conversion in 8/11 clones and 10/11 clones showed unchanged copies of the plasmid. Using co-transfection of two integrating plasmids, each containing a separate deletion in the xgprt reporter gene, the 27 times difference in extra-chromosomal recombination was found when the plasmids were cleaved at a distance from the reporter gene. When the plasmids were cleaved within the reporter gene, the co-transfection frequency was reduced in A-T, but was increased in normal cells. We conclude that A-T cell lines have not only a high frequency chromosomal and extra-chromosomal recombination, but also exhibit error-prone recombination of cleaved DNA.
Luo
C M
CM
Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Tang
W
W
Mekeel
K L
KL
DeFrank
J S
JS
Anné
P R
PR
Powell
S N
SN
D001260:Ataxia Telangiectasia / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002461:Cell Line, Transformed; D002934:Cinnamates; D004247:DNA / Q000096:biosynthesis* / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D006801:Humans; D006921:Hygromycin B / Q000031:analogs & derivatives / Q000494:pharmacology; D010430:Pentosyltransferases / Q000096:biosynthesis / Q000235:genetics; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis; D011995:Recombination, Genetic; D015183:Restriction Mapping; D017384:Sequence Deletion; D013539:Simian virus 40 / Q000235:genetics; D014162:Transfection
D002934:Cinnamates; D011994:Recombinant Proteins; D006921:Hygromycin B; C026273:hygromycin A; D004247:DNA; D010430:Pentosyltransferases; C024827:xanthine phosphoribosyltransferase