AI Article Synopsis

  • FoxM1 is a transcription factor that regulates many genes during the G(2) phase of the cell cycle, but its activity is normally restrained by an autoinhibitory mechanism.
  • Cyclin A/Cdk phosphorylation activates FoxM1 by overcoming this inhibition, allowing it to function effectively.
  • The protein B55α interacts with FoxM1 and promotes its inactivation by enhancing its dephosphorylation, ensuring that FoxM1 activation is limited to G(2) phase only.

Article Abstract

The forkhead transcription factor FoxM1 controls expression of a large number of genes that are specifically expressed during the G(2) phase of the cell cycle. Throughout most of the cell cycle, FoxM1 activity is restrained by an autoinhibitory mechanism, involving a repressor domain present in the N-terminal part of the protein. Activation of FoxM1 in G(2) is achieved by Cyclin A/Cyclin-dependent kinase (Cdk)-mediated phosphorylation, which alleviates autoinhibition by the N-terminal repressor domain. Here, we show that FoxM1 interacts with B55α, a regulatory subunit of protein phosphatase 2A (PP2A). B55α binds the catalytic subunit of PP2A, and this promotes dephosphorylation and inactivation of FoxM1. Indeed, we find that overexpression of B55α results in decreased FoxM1 activity. Inversely, depletion of B55α results in premature activation of FoxM1. The activation of FoxM1 that is observed upon depletion of B55α is fully dependent on Cyclin A/Cdk-mediated phosphorylation of FoxM1. Taken together, these data demonstrate that B55α acts to antagonize Cyclin A/Cdk-dependent activation of FoxM1, to ensure that FoxM1 activity is restricted to the G(2) phase of the cell cycle.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3190881PMC
http://dx.doi.org/10.1074/jbc.M111.253724DOI Listing

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