Continued initiation of DNA synthesis in arginine deprived Chinese hamster ovary cells

Abstract

When exponentially growing CHO cells were deprived of arginine (Arg), cell multiplication ceased after 12 h. but initiation of DNA synthesis continued: after 48 h of starvation with continuous [3H]thymidine exposure, 85% of the population had incorporated label, as detected autoradiographically. Consideration of the distribution of exponential cells in the various cell cycle phases leads to a calculation that most cells in G1 at the time that Arg was removed, as well as those in S, engaged in some DNA synthesis during starvation. In contrast, isoleucine (Ile) starved cells did not initiate DNA synthesis, as has been reported by others. Experiments with cells synchronized by mitotic selection confirmed this difference in Arg- and Ile- deprived behavior, but also showed that cells which underwent the mitosis → G1 transition during Arg starvation remained arrested in G1 (G0?). The results suggest that Arg deprived cells continue to maintain some proliferative function(s) while Ile deprived cells do not.