Isolation of Mutagen-Sensitive Chinese Hamster Cell Lines by Replica Plating

Cell lines with an increased sensitivity to mutagens, such as ultraviolet (UV) light, X-rays, alkylating compounds, and crosslinking agents, are defective in a cellular response to these agents. These responses include mechanisms that process DNA lesions, scavenge free radicals, or regulate cell-cycle progression. The molecular defects in cell lines derived from patients with inherited recessive disorders that combine cancer proneness with an abnormal response to DNA-damaging agents, such as xeroderma pigmentosum, ataxia telangiectasia, and Fanconi anemia, have been extensively studied (see , for example, Chapters 7 , 9 , 29 , and 44 ). However, such human diseases may not identify all possible cellular responses to mutagenic treatments, since only those defects that are manifested at the clinical level, and not lethal in vivo, can be detected. Therefore, in addition, many mutagen-sensitive mutants have been obtained in rodent cell lines. The availability of such mutants is essential to identify the genes involved, their products and functions, as well as to assess the biological consequences of their impact. It has also become evident that rodent cell mutants defective in DNA repair provide an important tool for the isolation of human genes complementing the defect in these mutants (see Chapter 7 ). Therefore, to dissect the cellular response to a specific mutagen, it is essential to have a comprehensive set of mutants with an increased sensitivity to the agent.