Role of polyamines in HeLa cell proliferation.

HeLa cells were synchronized for S phase DNA synthesis by the double thymidine block procedure and simultaneously depleted of putrescine and spermidine with the irreversible inhibitor of ornithine decarboxylase, alpha-difluoromethyl ornithine. S phase DNA synthesis was inhibited and cell proliferation was prevented in the cells in which polyamines were depleted by the inhibitor of ornithine decarboxylase. Nuclei prepared from synchronized, polyamine-depleted cells were almost totally inactivated for in vitro DNA synthesis. S phase DNA synthesis was restored and normal cell proliferation occurred if either putrescine, spermidine, or spermine was added to the medium during the synchronization of the cells in the presence of alpha-difluoromethyl ornithine. Nucleic prepared from cells synchronized in media containing the inhibitor but supplemented with a polyamine during the synchronization procedure were also completely active in the synthesis of DNA in vitro. The results indicate that polyamines are required for the replication of DNA in HeLa cells.