Cytogenetical characterisation of Chinese hamster 43-3B transferants with the amplified or non-amplified human DNA repair gene ERCC-1.
A comparative study on the biological responses to different mutagens (UV, 4NQO, MMC, MMS and EMS) was made on CHO wild-type cells (CHO-9), its UV-hypersensitive mutant 43-3B, and 2 types of its transferants, i.e., one containing a few copies of the human repair gene ERCC-1 and the other having more than 100 copies of ERCC-1 (due to gene amplification). Cell survival, chromosomal aberrations and SCEs were used as biological end-points. The spontaneous frequency of chromosomal aberrations in the transferants was less than found in 43-3B mutant cells, but still 2-3 times higher than in wild-type CHO cells. The spontaneous frequency of SCEs in the transferants was less than in 43-3B and similar to that of wild-type cells. The induction of SCEs by all tested agents in transferants was similar to that found in CHO-9 cells, while the mutant is known to respond with higher frequencies. ERCC-1 also bestowed resistance to MMS and EMS on the mutant to induction of chromosomal aberrations and cell killing to levels comparable with those of the wild-type strain. On the other hand ERCC-1 could not completely regain the repair proficiency against cell killing and induction of chromosomal aberrations by UV or MMC to the wild-type level. These results suggest that the ERCC-1 corrects the repair defect in CHO mutant cells, but it is unable to rectify fully the defect; probable reasons for this are discussed. However, amplified transferants (having more than 100 copies of the ERCC-1 gene) restored the impaired repair function in 43-3B to UV-, MMC- or 4NQO-induced DNA damage better than non-amplified transferants with a few copies of the ERCC-1. This difference may be due to the high amount of gene product involved in the excision repair process in the amplified cells.
Darroudi
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F
Department of Radiation Genetics and Chemical Mutagenesis, State University of Leiden, The Netherlands.
Westerveld
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A
Natarajan
A T
AT
D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity*; D000477:Alkylating Agents / Q000633:toxicity*; D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002869:Chromosome Aberrations; D006224:Cricetinae; D004260:DNA Repair; D005816:Genetic Complementation Test; D009154:Mutation; D009600:Nitroquinolines / Q000633:toxicity*; D012854:Sister Chromatid Exchange / Q000187:drug effects; D014162:Transfection; D014466:Ultraviolet Rays
D000477:Alkylating Agents; D009600:Nitroquinolines; D015112:4-Nitroquinoline-1-oxide