Control of DNA synthesis in tissue culture cells

Summary Eukaryotic DNA is functionally divided into thousands of replicons, each of which may be duplicated at a characteristic time within the DNA synthetic (S) period. Our approach toward an understanding of the molecular mechanisms which control orderly eukaryotic DNA synthesis has been: (a) to devise a method of cell synchrony in a suitable tissue culture system wherein all cells in the population enter and traverse the S period with a high degree of synchrony; (b) to determine, utilizing this system, precisely when during the S period critical events and macromolecular syntheses occur; and (c) to examine, by polyacrylamide-gel electrophoresis, the spectrum of proteins which become associated with chromatin during the S period in such a way as to suggest their involvement with DNA synthesis. Possible mechanisms for control are discussed based on the results presented here. Presented in the formal symposium on Mechanisms of Cellular Control at the 28th Annual Meeting of the Tissue Culture Association, New Orleans, Louisiana, June 6–9, 1977. The work reported in this communication was supported by NCI Grant CA 18612 to A.B.P.