Abstract
DNA replication intermediates in human melanoma cells have been investigated by using the drug aphidicolin, which inhibits DNA polymerase alpha. In untreated cells, Okazaki fragments and 10-kilobase (kb) DNA intermediates are formed. In aphidicolin-treated cells, the replication fork is stopped and there is no formation of DNA replication intermediates. However, 10-kb DNA intermediates formed before the drug blockade are ligated to high molecular weight DNA whereas already formed Okazaki fragments accumulate in the cell. Moreover, in cells released from aphidicolin inhibition there is preferential labeling of 10-kb DNA compared to Okazaki fragments. The 10-kb DNA and the Okazaki fragments, therefore, respond differently to aphidicolin.