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Mol Biol Cell 1994 Mar 01;53:323-38.
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Inhibition of cdc2 activation by INH/PP2A.

Lee TH , Turck C , Kirschner MW .

INH, a type 2A protein phosphatase (PP2A), negatively regulates entry into M phase and the cyclin B-dependent activation of cdc2 in Xenopus extracts. INH appears to be central to the mechanism of the trigger for mitotic initiation, as it prevents the premature activation of cdc2. We first show that INH is a conventional form of PP2A with a B alpha regulatory subunit. We next explore the mechanism by which it inhibits cdc2 activation by examining the effect of purified PP2A on the reaction pathways controlling cdc2 activity. Our results suggest that although PP2A inhibits the switch in tyrosine kinase and tyrosine phosphatase activities accompanying mitosis, this switch is a consequence of the inhibition of some other rate-limiting event. In the preactivation phase, PP2A inhibits the pathway leading to T161 phosphorylation, suggesting that this activity may be one of the rate-limiting events for transition. However, our results also suggest that the accumulation of active cdc2/cyclin complexes during the lag is only one of the events required for triggering entry into mitosis.

PubMed ID: 8049524
PMC ID: PMC301040
Article link: Mol Biol Cell

Species referenced: Xenopus
Genes referenced: ccnb1.2 cdk1 pold1 ptpa

References [+] :
Arion, cdc2 is a component of the M phase-specific histone H1 kinase: evidence for identity with MPF. 1988, Pubmed, Xenbase