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XB-ART-22953
EMBO J January 1, 1993; 12 (1): 53-63.
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Phosphorylation and activation of human cdc25-C by cdc2--cyclin B and its involvement in the self-amplification of MPF at mitosis.

Hoffmann I , Clarke PR , Marcote MJ , Karsenti E , Draetta G .


Abstract
We have investigated the mechanisms responsible for the sudden activation of the cdc2-cyclin B protein kinase before mitosis. It has been found previously that cdc25 is the tyrosine phosphatase responsible for dephosphorylating and activating cdc2-cyclin B. In Xenopus eggs and early embryos a cdc25 homologue undergoes periodic phosphorylation and activation. Here we show that the catalytic activity of human cdc25-C phosphatase is also activated directly by phosphorylation in mitotic cells. Phosphorylation of cdc25-C in mitotic HeLa extracts or by cdc2-cyclin B increases its catalytic activity. cdc25-C is not a substrate of the cyclin A-associated kinases. cdc25-C is able to activate cdc2-cyclin B1 in Xenopus egg extracts and to induce Xenopus oocyte maturation, but only after stable thiophosphorylation. This demonstrates that phosphorylation of cdc25-C is required for the activation of cdc2-cyclin B and entry into M-phase. Together, these studies offer a plausible explanation for the rapid activation of cdc2-cyclin B at the onset of mitosis and the self-amplification of MPF observed in vivo.

PubMed ID: 8428594
PMC ID: PMC413175
Article link:


Species referenced: Xenopus
Genes referenced: ccnb1.2 cdc25c cdk1 pold1 rasgrf1

References [+] :
Amon, Regulation of p34CDC28 tyrosine phosphorylation is not required for entry into mitosis in S. cerevisiae. 1992, Pubmed, Xenbase