DNA-repair mechanisms : symposium, Schloss Reinhartshausen/Rhein, Oct. 4th/5th, 1971 / chairman H. Altmann.

Date:
[1972]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: DNA-repair mechanisms : symposium, Schloss Reinhartshausen/Rhein, Oct. 4th/5th, 1971 / chairman H. Altmann. Source: Wellcome Collection.

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    ing treatment of cells with mustard gas. At the D 0 dose of mustard gas for HeLa cells less than 1 molecule of protein (mol. wt. 1 X 10 5 ) in 2000 but every molecule of DNA of mol. wt. 3 X 10 8 daltons was alkylated. Hence protein enzymes involved in the replication of DNA are not likely to have been inhib ited by these concentrations of mustard gas. Indeed no inhibition of thymidine kinase could be achieved even with appreciably higher concentrations of mustard gas than were required to inhibit DNA synthesis. Chemical, biochemical and biological observations indicate that cells recover from the otherwise lethal effect of DNA alkylations thus implying the existence Effect of mustard q as on DNA synthesis in HeLa cells Time after harvest (hrs) Fig. 1. The effect of treatment with mustard gas during the Gi phase of the cell cycle (ar rowed A) on subsequent DNA synthesis in a synchronous population of HeLa cells. The cells were treated with mustard gas (0.075 //g/ml in ether 0.05%) and the extent of DNA synthesis in treated and untreated cells measured at various times thereafter by the up take of [ 3 H]TdR into cold TCA-insoluble material in a 1 ml aliquot of cells. #—# Control; O—O 0.075 //g/ml mustard gas. of a mechanism(s) for repairing lesions in DNA. As can be seen in Fig. 1 (and also in Fig. 5, which shows the effects of half mustard gas on DNA synthesis) those cells which do divide after the initially extended S phase and subsequent mitotic delay do not exhibit any extension of the S phase or mitotic delay in the following cell cycle but divide thereafter with a normal