Actinomycin D and [formula omitted], inhibitors of nuclear replication in HeLa cells

Abstract

The effects of actinomycin D and p- fluorophenylalanine on DNA synthesis and cell division in synchronized cultures of HeLa cells were examined. If added early in the period of DNA synthesis, actinomycin D prevented replication of a portion of the DNA and blocked division of the cells. If added 2 h or more after initiation of DNA synthesis actinomycin D prevented cell division but had little effect on DNA synthesis. p- Fluorophenylalanine did not affect DNA synthesis but prevented cell division if added during the period of replication of DNA. These processes were characterized by the time of their occurrence in the cell cycle and by their relative sensitivity to the drugs. The findings support the concept that cell replication requires the synthesis of specific RNA's and protein at definite times in the cell cycle, and increases our understanding of the function of these sequential phenomena in nuclear replication.