The relationship between 3-hydroxy-3-methylglutaryl (HMG) CoA reductase activity mevalonate:NADP(+) oxidoreductase (CoA-acylating), EC 1.1.1.34 and DNA synthesis was studied in synchronized cultures of BHK-21 cells. During a 24-hr period of cell replication, two phases of accelerated thymidine incorporation into DNA corresponding to two S phases of the cell cycle occurred. A marked increase in activity of HMG CoA reductase was consistently observed at or just prior to each of these peaks of DNA synthesis. Moreover, when HMG CoA reductase activity was suppressed by the competitive inhibitor compactin, the normal S-phase burst of DNA synthesis was specifically and totally prevented. Finally, the compactin-induced inhibition of DNA synthesis could be completely reversed within minutes by the addition of mevalonate, the product of the HMG CoA reductase reaction. By contrast, addition of cholesterol-rich lipoproteins had no effect upon DNA synthesis in compactin-treated cells. These data demonstrate that HMG CoA reductase activity, and therefore the production of mevalonate, plays an essential role in the synthesis of DNA specifically during the S phase of the cell cycle. Moreover, the results indicate that this function of mevalonate in regulating DNA replication is independent of its conversion to cholesterol.
Quesney-Huneeus et al. (Mon,) studied this question.