Investigation of the mutagenic specificity of X-rays using a retroviral shuttle vector in CHO cells.
In some biological systems ionizing radiation appears to induce large deletions and rearrangements, while in others point mutations predominate the mutational spectrum. Moreover, while the point mutations are often randomly distributed, some systems exhibit "hot spots." Retroviral shuttle vectors are particularly useful for investigating the basis of these differences since the genetic target can be conveniently analyzed in a variety of host backgrounds and genomic locations. We have studied the mutational specificity of X-rays in a Chinese hamster ovary cell line (CHO) containing a stably integrated retroviral shuttle vector, carrying the CHO aprt cDNA as the genetic target. Cells were irradiated with 7 Gy using a 180 kVp X-ray source. The predominant mutation (87% of all APRT mutants), as determined by Southern analysis, was the complete deletion of the shuttle vector construct. In addition, 23 APRT mutants, carrying an apparently intact shuttle vector, were characterized at the sequence level: 5 were transitions, 9 were transversions, 3 were small deletions or insertions, 4 were frameshifts, and 2 were small rearrangements. Although the type and the location of the point mutations characterized appeared largely random, small deletions, insertions, and frameshifts were frequently associated with direct sequence repeats.
Skandalis
A
A
York University, Department of Biology, Toronto, Ontario, Canada.
Grosovsky
A J
AJ
Drobetsky
E A
EA
Glickman
B W
BW
D000228:Adenine Phosphoribosyltransferase / Q000235:genetics*; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D016466:CHO Cells / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000528:radiation effects*; D004252:DNA Mutational Analysis / Q000379:methods*; D004251:DNA Transposable Elements / Q000528:radiation effects; D016368:Frameshift Mutation; D017353:Gene Deletion; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017354:Point Mutation; D012044:Regression Analysis; D012190:Retroviridae / Q000235:genetics*
D004251:DNA Transposable Elements; D004247:DNA; D000228:Adenine Phosphoribosyltransferase