Uncoupled cell cycle without mitosis induced by a protein kinase inhibitor, K-252a.

Abstract

Abstract. The staurosporine analogues, K-252a and RK286C, 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 conwo major events in the normal cell cycle, nuclear DNA replication in S phase and nuclear division in M phase, are tightly coupled with each other. Comple tion of one is an essential requirement for initiation of the other (Hartwell et al., 1974;Hartwell, 1978). For example, mitosis is dependent on the completion of S phase; blocking DNA replication prevents the initiation ofmitosis in somatic cells. The molecular mechanism of this coupling has been studied using early embryos (Dasso and Newport, 1990), several mutant cell lines (Nishimoto et al., 1978;Osmani et al., 1988 ;Weinert and Hartwell, 1988 ;Enoch and Nurse, 1990), and drugs which cause premature mitosis in the absenceofchromosome replication (Schlegel and Pardee,1986 ;Schlegel et al ., 1990).DNA replication is reciprocally dependent on previous mitosis and is controlled so as to occur precisely once in each cell cycle. An important clue to understanding the mechanism underlying this regulation was provided by Rao and Johnson (1970), who fused G2-phase cells with S-phase cells and demonstrated that a nondiffusible factor is responsible for blocking DNA re-replication in the G2 nucleus . Recently, Blow and Laskey (1988) proposed a model based on observations of chromosome replication in Xenopus egg extracts. They assumed that an essential factor for DNA rereplication is supplied from the cytoplasm to the chromosomes through breakdown of the nuclear envelope in mito- tinuous treatment with K252a, indicating that the agent induced several rounds of the incompl cycle without mitosis . Although the effectiv tration of K-252a did not cause significant i of affinity-purified p34cdc2 protein kinase activity in vitro, in vivo the full activation of p34cdc2 kinase during the G2/M was blocked by K252a . 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 .to cell concenibition sis . However, very little is kno...

Interaction of Xenopus Cdc2·Cyclin A1 with the Origin Recognition Complex

“…Conditional mutations of cdc2 and deletion of cdc13, the B-type cyclin in Schizosaccharomyces pombe, promote over-replication (51,52). Similarly, inhibition of protein kinases in G 2 in mammalian cells makes them competent to replicate again (53,54) and causes MCM proteins to rebind to replicating chromatin (29). In Xenopus egg extracts, the rebinding of MCM proteins to chromatin is actively prevented by the accumulation of cyclin A or E in sperm nuclei (30).…”

K252a is highly effective in suppressing the growth of human endometrial cancer cells, but has little effect on normal human endometrial epithelial cells

“…K252a was found to inhibit protein kinase C (3,4), the cAMP-(3) and cGMP-dependent protein kinase (3), myosine light chain kinase (5), Ca 2+ /calmodulin-dependent protein kinases (CaMKs) (6) and cell cycle regulatory kinases such as Cdc2 (7). Specifically, K252a blocks the nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) activity in rat pheochromocytoma PC-12 and neuroblastoma cell lines by inhibiting TrkA and -B tyrosine kinase activity (8)(9)(10).…”

Effects of thrombopoietin, interleukin-3 and the kinase inhibitor K-252a on growth and polyploidization of the megakaryocytic cell line M-07e

“…In contrast, K-252a effectively stimulated polykaryon formation ( Figure 5), thus confirming previous results using other cells. 20,21 In contrast to the leukemia cell lines Nalm-6 (B-precursor cell line), TOM-1 (B-precursor cell line) and Mono-Mac-6 (monocytic cell line) (data not shown), M-07e and K-562 cells were responsive to K-252a showing an increase from less than 3% to 17% and 48% polynuclear cells, respectively, after stimulation with this reagent (Figure 5a, b). The flow cytometry data were confirmed by May-Grü nwald-Giemsa preparations (data not shown).…”

“…To mimic this event, we applied K-252a, a well-known inducer of endomitosis. 20,21 After 3 days, 17% of the originally mononuclear M-07e cells had two or more nuclei. This effect was even stronger in HL-60 and K-562 cells with up to half of the cells containing two, three or more nuclei.…”