Early dihydrofolate reductase gene amplification events in CHO cells usually occur on the same chromosome arm as the original locus.
Barbara J. Trask,Joyce L. Hamlin +1 more
TLDR
These results are not consistent with models in which initial amplification events occur by over-replication of the parental locus followed by recombination in loco, but are most compatible with either sister chromatid exchange between widely separated sites or with a form of conservative intrachromosomal duplication analogous to transposition in bacteria.Abstract:
We used fluorescence in situ hybridization to examine the products of early DNA sequence amplification events in CHO cells. Nine independent populations of cells were selected for resistance to 0.4 |XM methotrexate (MTX), and mitotic chromosome spreads were hybridized to a mixture of cloned cosmids representing —273 kb of contiguous DNA sequence from the dihydrofolate reductase (DHFR) locus. Of the nine populations, eight contain cells that have amplified the DHFR domain. Cells in the remaining population displayed only the two single-copy loci on chromosomes 2 and Z2. Of the eight amplificants, one carries amplified DHFR genes on chromosome 1, six on chromosome Z2, and one on an unidentified chromosome. Some cultures carry additional amplified genes on other chromosomes, probably resulting from bridge/breakage/fusion cycles or translocations. In six of the eight amplificants, both single-copy parental loci are detected at their original positions, and amplicon clusters are situated at least 50 megabases (Mb) away on the same chromosome arm, often at the termini. Amplification occurred at or close to the original site of the DHFR gene in only one population. Our results are not consistent with models in which initial amplification events occur by over-replication of the parental locus followed by recombination in loco. Because amplified DHFR sequences occur most often on the same chromosome arm as the parental DHFR gene but at a considerable distance from it, our results are most compatible with either sister chromatid exchange between widely separated sites or with a form of conservative intrachromosomal duplication analogous to transposition in bacteria.read more
Citations
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Altered cell cycle arrest and gene amplification potential accompany loss of wild-type p53.
Laura R. Livingstone,Alicia White,Alicia White,Jason Sprouse,Jason Sprouse,Elizabeth Livanos,Elizabeth Livanos,Tyler Jacks,Thea D. Tlsty,Thea D. Tlsty +9 more
TL;DR: Loss of wild-type p53 may lead to amplification, possibly caused by changes in cell cycle progression, since tumor cells with wild- type p53 have the ability to amplify genes.
Journal ArticleDOI
Defects in a cell cycle checkpoint may be responsible for the genomic instability of cancer cells.
Journal ArticleDOI
ERBB2 amplification in breast cancer analyzed by fluorescence in situ hybridization.
Olli-P. Kallioniemi,Anne Kallioniemi,Wayne Kurisu,Ann Thor,Ling-Chun Chen,Helene S. Smith,Frederic M. Waldman,Daniel Pinkel,Joe W. Gray +8 more
TL;DR: Quantitative analysis of ERBB2 amplification by FISH may improve prognostic assessments based on the pattern of amplification and detection of heavily amplified tumor cell subpopulations.
Journal ArticleDOI
Genomic Instability Induced by Ionizing Radiation
TL;DR: This review summarizes the current status of knowledge about radiation-induced genomic instability and discusses events and processes likely to be involved in the initiation and perpetuation of the unstable phenotype, the potential role of epigenetic factors in influencing the onset of genomic instability, and the delayed effects of cellular exposure to ionizing radiation.
PatentDOI
Comparative genomic hybridization
TL;DR: In this paper, the authors used in situ hybridization to detect abnormal nucleic acid sequence copy numbers in one or more genomes wherein repetitive sequences that bind to multiple loci in a reference chromosome spread are either substantially removed and/or their hybridization signals suppressed.
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