Gene rearrangements induced by the DNA double-strand cleaving agent neocarzinostatin: conservative non-homologous reciprocal exchanges in an otherwise stable genome.
Among a collection of 74 aprt mutations induced by treatment of plateau phase Chinese hamster ovary CHO cells with the radiomimetic DNA double-strand cleaving agent neocarzinostatin, nine were large-scale rearrangements. Molecular analysis indicated that all nine were highly conservative, non-homologous reciprocal exchanges, most of which were intrachromosomal as determined by fluorescence in situ hybridization. All but one of the parental sequences contained potential double-strand cleavage sites positioned such that the observed rearrangements could be explained by drug-induced double-strand breakage followed by trimming, templated patching and ligation of the exchanged ends. Predicted non-complementary 3' overhangs were often preserved in the newly formed junctions, suggesting alignment-based fill-in of the overhangs. Banding of metaphase spreads of these mutants, and of a number of mutants induced by the functionally similar compound bleomycin, revealed that bleomycin-induced reciprocal exchange mutants had multiple additional chromosome alterations and considerable chromosomal heterogeneity within each mutant line. In contrast, neocarzinostatin-induced reciprocal exchange mutants, as well as bleomycin-induced base substitution and single base deletion mutants, retained stable pseudodiploid karyotypes similar to that of the parent line. Thus, some reciprocal exchanges arising from misjoining of double-strand breaks were associated with global chromosomal instability, while other ostensibly similar events were not.
Wang
Peng
P
Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298-0230, USA.
Lee
Jae Wan
JW
Yu
Yin
Y
Turner
Kristi
K
Zou
Ying
Y
Jackson-Cook
Colleen K
CK
Povirk
Lawrence F
LF
D000228:Adenine Phosphoribosyltransferase / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage; D016678:Genome; D008969:Molecular Sequence Data; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D011995:Recombination, Genetic; D009353:Zinostatin / Q000633:toxicity*
D009153:Mutagens; D009353:Zinostatin; D000228:Adenine Phosphoribosyltransferase