Coupling of mitosis to the completion of S phase in Xenopus occurs via modulation of the tyrosine kinase that phosphorylates p34cdc2.

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摘要：

In cell-free extracts derived from Xenopus eggs which oscillate between S phase and mitosis, incompletely replicated DNA blocks the activation of p34 cdc2 -cyclin by maintaining p34 cdc2 in a tyrosine-phosphorylated form. We used a recombinant cyclin fusion protein to generate a substrate to measure the ability of the tyrosine kinase(s) to phosphorylate and inactivate p34 cdc2 in the absence of tyrosine phosphatase activity. p34 cdc2 tyrosine phosphorylation is highly regulated during the cell cycle, being elevated in S phase and attenuated in mitosis. The elevation in p34 cdc2 tyrosine phosphorylation rate occurs in response to the presence of incompletely replicated DNA. Moreover, okadaic acid and caffeine, which uncouple the dependence of mitosis on the completion of S phase, increase unphosphorylated p34 cdc2 by attenuating tyrosine kinase function. These data indicate that the control system, which monitors the state of DNA replication, modulates the function of the tyrosine kinase by a phosphorylation/dephosphorylation mechanism, ensuring that mitosis occurs only when S phase is complete.

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关键词：

CULTURED CARDIOMYOCYTE ANOXIA PHOSPHOLIPID DEGRADATION PHOSPHOLIPASE-C

DOI：

10.1016/0092-8674(92)90153-4

被引量：

513

年份：

1992