EHRLICH ASCITES TUMOR (EAT) CHALONE EFFECTS ON NASCENT DNA SYNTHESIS AND DNA POLYMERASE ALPHA AND BETA

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Abstract
EAT chalone effects on nascent DNA synthesis and DNA polymerase were examined. Concentration related inhibition of 3H-thymidine (3H-TdR) incorporation into EAT cell DNA was noted over a chalone range of 50-200 .mu.g/ml. RNA synthesis was not affected, but protein synthesis decreased an average of 82% during 3 h. Nascent DNA pulse labeled for 2 min was normally incorporated into bulk DNA in the presence of chalone, but crude .alpha.- and .beta.-polymerase activities were inhibited. Crude DNA polymerase from C3H mouse kidney and spleen was also partially inhibited by EAT chalone, suggesting nonspecific inhibition of DNA polymerase. Preincubation studies of chalone with crude EAT DNA polymerase or gapped DNA primer had no effect on chalone activity. Chalone may control mitotic activity by inhibiting .alpha.- and .beta.-polymerase activity, thereby decreasing nascent DNA synthesis. Nascent DNA is incorporated normally into bulk DNA in the presence of chalone, indicating that DNA ligase is not inhibited.

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