An ionizing radiation-sensitive CHO mutant cell line: irs-20. IV. Genetic complementation, V(D)J recombination and the scid phenotype.
The genetic defect responsible for hypersensitivity of Chinese hamster ovary (CHO) irs-20 cells to ionizing radiation was found to be recessive in nature and could be complemented to produce wild-type radiosensitivity in irs-20/human hybrids. The radiosensitivities of six hybrid clones were determined based on their colony-forming ability under continuous irradiation at 6 cGy/h. A parallel cytogenetic analysis revealed a concordance between the presence or absence of human chromosome 8 and the resistant or sensitive phenotype. Confirming evidence was obtained using human chromosome 8-specific PCR primers. Positive amplification was obtained in hybrids with wild-type radiosensitivity, while no amplification was obtained in sensitive hybrids. Complementation analysis between radiosensitive CHO irs-20 and murine scid cell lines was carried out to determine whether the defects leading to their ionizing radiation hypersensitivity could be corrected by genetic complementation in the hybrids. Complementation did not occur. A transient V(D)J recombination assay after the introduction of the RAG1 and RAG2 genes indicated that the V(D)J recombination ability of the CHO irs-20 cells was about 10% of that for the CHO wild-type cells for signal join formation with an 80% joining fidelity and only 3% of the parental level for coding join formation. These data show that murine scid and irs-20 mutant hamster cells fall into the same complementation group and show similar defects in V(D)J recombination.
Lin
J Y
JY
Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523, USA.
Mühlmann-Diaz
M C
MC
Stackhouse
M A
MA
Robinson
J F
JF
Taccioli
G E
GE
Chen
D J
DJ
Bedford
J S
JS
D000818:Animals; D016466:CHO Cells / Q000528:radiation effects*; D002874:Chromosome Mapping; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics*; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics*; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins; D015321:Gene Rearrangement; D005808:Genes, Recessive; D005816:Genetic Complementation Test; D018398:Homeodomain Proteins; D006801:Humans; D006822:Hybrid Cells / Q000201:enzymology / Q000528:radiation effects*; D051379:Mice; D016513:Mice, SCID / Q000235:genetics*; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics / Q000502:physiology; D011836:Radiation Tolerance / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011995:Recombination, Genetic; D016511:Severe Combined Immunodeficiency / Q000201:enzymology / Q000235:genetics*; D014162:Transfection; D045567:VDJ Recombinases
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D011506:Proteins; C499311:RAG2 protein, human; C499308:Rag2 protein, mouse; D011993:Recombinant Fusion Proteins; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D004254:DNA Nucleotidyltransferases; D045567:VDJ Recombinases