Abstract
During cell division, progression through mitosis is driven by a protein phosphorylation wave. This wave namely depends on an activation-inactivation cycle of cyclin B-dependent kinase (Cdk) 1 while activities of major protein phosphatases, like PP1 and PP2A, appear directly or indirectly repressed by Cdk1. However, how Cdk1 inactivation is coordinated with reactivation of major phosphatases at mitosis exit still lacks substantial knowledge. We show here that activation of PP2A-B55, a major mitosis exit phosphatase, required the phosphatase Fcp1 downstream Cdk1 inactivation in human cells. During mitosis exit, Fcp1 bound Greatwall (Gwl), a Cdk1-stimulated kinase that phosphorylates Ensa/ARPP19 and converts these proteins into potent PP2A-B55 inhibitors during mitosis onset, and dephosphorylated it at Cdk1 phosphorylation sites. Fcp1-catalyzed dephosphorylation drastically reduced Gwl kinase activity towards Ensa/ARPP19 promoting PP2A-B55 activation. Thus, Fcp1 coordinates Cdk1 and Gwl inactivation to derepress PP2A-B55, generating a dephosphorylation switch that drives mitosis progression.
Highlights
We recently reported a critical, transcription-independent, role for the essential RNA polymerase IIcarboxy-terminal domain (RNAP II-CTD) phosphatase Fcp1 in Cdk1 inactivation at the end of mitosis (Visconti et al, 2012)
We noticed that Fcp1 depletion impaired bulk mitotic protein dephosphorylation upon chemical inhibition of Cdk1 in non-transcribing mitotic cell extracts (Visconti et al, 2012)
In which Fcp1 expression was downregulated in HeLa cells by small interfering RNAs, we found that dephosphorylations of bulk K/HpSP motif and pT481-PRC1 at
Summary
We recently reported a critical, transcription-independent, role for the essential RNA polymerase IIcarboxy-terminal domain (RNAP II-CTD) phosphatase Fcp in Cdk inactivation at the end of mitosis (Visconti et al, 2012). Gwl-Fcp interaction was detected during mitosis exit in non-transformed, telomerase-immortalized, human retinal pigment epithelium cells hTERT-RPE1 (Figure 3—figure supplement 1) Taken together, these data suggest that Fcp bound and dephosphorylated Gwl at S90 and S453, and possibly at other Cdk1-dependent sites, during mitosis exit and that Fcp1-catalyzed dephosphorylation lowered Gwl activity towards Ensa/ARPP19, allowing PP2A-B55 to autoactivate. Like for Gwl dephosphorylation, prolonging Cdk inhibitor treatment up to 30 min resulted in a reduction of Ensa kinase activity of Gwl in Fcp1-depleted cells and, again, we cannot rule out whether this is due to the fact that other phosphatases or residual Fcp dampened Gwl activity after substantial time from Cdk inactivation (Figure 4—figure supplement 2). Along with other recently described phosphatase activation networks (Lorca and Castro, 2013; Porter et al, 2013; Nijenhuis et al, 2014; Grallert et al, 2015), this pathway contributes to ensure coordinated reversal of mitotic phosphorylations to grant correct completion of mitosis
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
