Uncoupled cell cycle without mitosis induced by a protein kinase inhibitor, K-252a.
The staurosporine analogues, K-252a and RK-286C, were found to cause DNA re-replication in rat diploid fibroblasts (3Y1) without an intervening mitosis, producing tetraploid cells. Analysis of cells synchronized in early S phase in the presence of K-252a revealed that initiation of the second S phase required a lag period of 8 h after completion of the previous S phase. Reinitiation of DNA synthesis was inhibited by cycloheximide, actinomycin D, and serum deprivation, but not by Colcemid, suggesting that a functional G1 phase dependent on de novo synthesis of protein and RNA is essential for entry into the next S phase. In a src-transformed 3Y1 cell line, as well as other cell lines, giant cells containing polyploid nuclei with DNA contents of 16C to 32C were produced by continuous treatment with K-252a, indicating that the agent induced several rounds of the incomplete cell cycle without mitosis. Although the effective concentration of K-252a did not cause significant inhibition of affinity-purified p34cdc2 protein kinase activity in vitro, in vivo the full activation of p34cdc2 kinase during the G2/M was blocked by K-252a. On the other hand, the cyclic fluctuation of partially activated p34cdc2 kinase activity peaking in S phase still continued. These results suggest that a putative protein kinase(s) sensitive to K-252a plays an important role in the mechanism for preventing over-replication after completion of previous DNA synthesis. They also suggest that a periodic activation of p34cdc2 is required for S phases in the cell cycle without mitosis.
Usui
T
T
Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo, Japan.
Yoshida
M
M
Abe
K
K
Osada
H
H
Isono
K
K
Beppu
T
T
D000818:Animals; D002227:Carbazoles / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D002460:Cell Line; D004171:Diploidy; D005347:Fibroblasts / Q000166:cytology; D005434:Flow Cytometry; D015726:Giant Cells / Q000166:cytology; D026121:Indole Alkaloids; D008938:Mitosis; D047428:Protein Kinase Inhibitors; D051381:Rats; D016196:S Phase / Q000187:drug effects
D002227:Carbazoles; D026121:Indole Alkaloids; D047428:Protein Kinase Inhibitors; C049985:staurosporine aglycone