Induction of DNA synthesis by microtubule depolymerization is mediated by actin filaments.

Colcemid (0.4 microgram/ml) induced DNA synthesis in quiescent chick embryo fibroblasts, and increased the amount of F-actin. Cytochalasin D, which disorganized actin filaments, inhibited the stimulation of DNA synthesis by colcemid. These results suggest that actin filaments are involved in the sequence of events leading from the depolymerization of microtubules to the initiation of DNA synthesis. They also demonstrate that depolymerization of microtubules can influence the amount of F-actin in the cell.