Genetic evidence that aphidicolin inhibits in vivo DNA synthesis in Chinese hamster ovary cells

Abstract

Using a genetic approach, Chinese hamster ovary (CHO) cells sensitive (aphS) and resistant (aphR) to aphidicolin were grown in the presence or absence of various DNA polymerase inhibitors, and the newly synthesized DNA isolated from [32P]dNMP-labelled, detergent-permeabilized cells, was characterized after fractionation by gel electrophoresis. The particular aphR mutant CHO cell line used was one selected for resistance to aphidicolin and found to possess an altered DNA polymerase of the alpha-family. The synthesis of a 24 kb replication intermediate was inhibited in wild-type CHO cells grown in the presence of aphidicolin, whereas the synthesis of this replication intermediate was not inhibited by this drug in the mutant CHO cells or in the aphidicolin-resistant somatic cell hybrid progeny constructed by fusion of wild-type and mutant cell lines. Arabinofuranosylcytosine (ara-C), like aphidicolin, inhibited the synthesis of this 24 kb DNA replication intermediate in the wild-type CHO cells but not in the aphR mutant cells. However, carbonyldiphosphonate (COMDP) inhibited the synthesis of the 24 kb replication intermediate in both wild-type and mutant cells. N2-(p-n-Butylphenyl)-2' deoxyguanisine-5'-triphosphate (BuPdGTP) was found to inhibit the formation of Okazaki fragments equally well in the wild-type and mutant cell lines and thus led to inhibition of synthesis of DNA intermediates in both cases. It appears that aphidicolin and ara-C both affect a common target on the DNA polymerase, which is different from that affected by COMDP in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)