TY - JOUR
T1 - Identification of defective illegitimate recombinational repair of oxidatively-induced DNA double-strand breaks in ataxia-telangiectasia cells
AU - Dar, Mubasher E.
AU - Winters, Thomas A.
AU - Jorgensen, Timothy J.
N1 - Funding Information:
The shuttle vector, pZ189, and the indicator strain, MBM7070, were kindly provided by M. Seidman, and Y. Shiloh generously provided the FT169A cells. We thank H. Yang for assistance with DNA sequencing, and B. Trock for assistance with statistical analysis. We also thank M. Seidman, M. Kohli, P. Russell, and Y. Shiloh for helpful discussions. This work was supported by a grant (#9307-0016) from the National Aeronautics and Space Administration. The DNA sequence analysis was performed on a Perkin-Elmer sequencer 377A by the Lombardi Cancer Center's Macromolecular Synthesis and Sequencing Shared Resource which is supported in part by U.S. Public Health Service Grant P30-CA-51008.
PY - 1997/9
Y1 - 1997/9
N2 - Ataxia-telangiectasia (A-T) is an autosomal-recessive lethal human disease. Homozygotes suffer from a number of neurological disorders, as well as very high cancer incidence. Heterozygotes may also have a higher than normal risk of cancer, particularly for the breast. The gene responsible for the disease (ATM) has been cloned, but its role in mechanisms of the disease remain unknown. Cellular A-T phenotypes, such as radiosensitivity and genomic instability, suggest that a deficiency in the repair of DNA double-strand breaks (DSBs) may be the primary defect; however, overall levels of DSB rejoining appear normal. We used the shuttle vector, pZ189, containing an oxidatively-induced DSB, to compare the integrity of DSB rejoining in one normal and two A-T fibroblast cell lines. Mutation frequencies were two-fold higher in A-T cells, and the mutational spectrum was different. The majority of the mutations found in all three cell lines were deletions (44-63%). The DNA sequence analysis indicated that 17 of the 17 plasmids with deletion mutations in normal cells occurred between short direct-repeat sequences (removing one of the repeats plus the intervening sequences), implicating illegitimate recombination in DSB rejoining. The combined data from both A-T cell lines showed that 21 of 24 deletions did not involve direct-repeats sequences, implicating a defect in the illegitimate recombination pathway. These findings suggest that the A-T gene product may either directly participate in illegitimate recombination or modulate the pathway. Regardless, this defect is likely to be important to a mechanistic understanding of this lethal disease.
AB - Ataxia-telangiectasia (A-T) is an autosomal-recessive lethal human disease. Homozygotes suffer from a number of neurological disorders, as well as very high cancer incidence. Heterozygotes may also have a higher than normal risk of cancer, particularly for the breast. The gene responsible for the disease (ATM) has been cloned, but its role in mechanisms of the disease remain unknown. Cellular A-T phenotypes, such as radiosensitivity and genomic instability, suggest that a deficiency in the repair of DNA double-strand breaks (DSBs) may be the primary defect; however, overall levels of DSB rejoining appear normal. We used the shuttle vector, pZ189, containing an oxidatively-induced DSB, to compare the integrity of DSB rejoining in one normal and two A-T fibroblast cell lines. Mutation frequencies were two-fold higher in A-T cells, and the mutational spectrum was different. The majority of the mutations found in all three cell lines were deletions (44-63%). The DNA sequence analysis indicated that 17 of the 17 plasmids with deletion mutations in normal cells occurred between short direct-repeat sequences (removing one of the repeats plus the intervening sequences), implicating illegitimate recombination in DSB rejoining. The combined data from both A-T cell lines showed that 21 of 24 deletions did not involve direct-repeats sequences, implicating a defect in the illegitimate recombination pathway. These findings suggest that the A-T gene product may either directly participate in illegitimate recombination or modulate the pathway. Regardless, this defect is likely to be important to a mechanistic understanding of this lethal disease.
KW - Ataxia telangiectasia
KW - DNA repair
KW - DNA strand break
KW - Illegitimate recombination
KW - Mutagenesis
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U2 - 10.1016/S0921-8777(97)00021-9
DO - 10.1016/S0921-8777(97)00021-9
M3 - Article
C2 - 9330613
AN - SCOPUS:0030807476
SN - 0921-8777
VL - 384
SP - 169
EP - 179
JO - Mutation Research - DNA Repair
JF - Mutation Research - DNA Repair
IS - 3
ER -