Plk1 Regulates Activation of the Anaphase Promoting Complex by Phosphorylating and Triggering SCF TrCP-dependent Destruction of the APC Inhibitor Emi1

Department of Pathology, Stanford University School of Medicine, Palo Alto, CA 94305, USA.
Molecular Biology of the Cell (Impact Factor: 4.55). 01/2005; 15(12):5623-34. DOI: 10.1091/mbc.E04-07-0598
Source: PubMed

ABSTRACT Progression through mitosis requires activation of cyclin B/Cdk1 and its downstream targets, including Polo-like kinase and the anaphase-promoting complex (APC), the ubiquitin ligase directing degradation of cyclins A and B. Recent evidence shows that APC activation requires destruction of the APC inhibitor Emi1. In prophase, phosphorylation of Emi1 generates a D-pS-G-X-X-pS degron to recruit the SCF(betaTrCP) ubiquitin ligase, causing Emi1 destruction and allowing progression beyond prometaphase, but the kinases directing this phosphorylation remain undefined. We show here that the polo-like kinase Plk1 is strictly required for Emi1 destruction and that overexpression of Plk1 is sufficient to trigger Emi1 destruction. Plk1 stimulates Emi1 phosphorylation, betaTrCP binding, and ubiquitination in vitro and cyclin B/Cdk1 enhances these effects. Plk1 binds to Emi1 in mitosis and the two proteins colocalize on the mitotic spindle poles, suggesting that Plk1 may spatially control Emi1 destruction. These data support the hypothesis that Plk1 activates the APC by directing the SCF-dependent destruction of Emi1 in prophase.

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Available from: David V Hansen, May 08, 2014
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    • "By knocking down Cdh1 or inhibiting Plk1 activity during G2 we wanted to test whether Plk1 and APC/ C activities can independently promote centriole disengagement in this phase of the cell cycle. Although centriole disengagement/ reduplication are reported to occur in a Plk1 activity dependent fashion in G2 (Lončarek et al., 2010), we re-examined this issue because that Plk1 phosphorylates Emi1 to target it for SCF-Trcp1 mediated destruction (Guardavaccaro et al., 2003; Margottin- Goguet et al., 2003; Hansen et al., 2004; Moshe et al., 2004). Thus, inhibition of Plk1 activity starting before cells reach G2 (Lončarek et al., 2010) should also block Emi1 destruction thereby inhibiting APC/C activity; the resulting lack of centriole disengagement in the absence of Plk1 and APC/C activity would thus be expected (Tsou et al., 2009). "
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    ABSTRACT: Mother-daughter centriole disengagement, the necessary first step in centriole duplication, involves Plk1 activity in early mitosis and separase activity after APC/C activity mediates securin degradation. Plk1 activity is thought to be essential and sufficient for centriole disengagement with separase activity playing a supporting but non-essential role. In separase null cells, however, centriole disengagement is substantially delayed. The ability of APC/C activity alone to mediate centriole disengagement has not been directly tested. We investigate the interrelationship between Plk1 and APC/C activities in disengaging centrioles in S or G2 HeLa and RPE1 cells, cell types that do not reduplicate centrioles when arrested in S phase. Knockdown of the interphase APC/C inhibitor Emi1 leads to centriole disengagement and reduplication of the mother centrioles, though this is slow. Strong inhibition of Plk1 activity, if any, during S does not block centriole disengagement and mother centriole reduplication in Emi1 depleted cells. Centriole disengagement depends on APC/C-Cdh1 activity, not APC/C-Cdc20 activity. Also, Plk1 and APC/C-Cdh1 activities can independently promote centriole disengagement in G2 arrested cells. Thus, Plk1 and APC/C-Cdh1 activities are independent but slow pathways for centriole disengagement. By having two slow mechanisms for disengagement working together, the cell ensures that centrioles will not prematurely separate in late G2 or early mitosis, thereby risking multipolar spindle assembly, but rather disengage in a timely fashion only late in mitosis.
    Biology Open 11/2012; 1(11):1153-60. DOI:10.1242/bio.20122626 · 2.42 Impact Factor
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    • "Entry and progression of mitosis is tightly regulated by multiple kinases including Aurora-A (Marumoto et al., 2005). Mitotic entry is controlled by the activation of cyclin-dependent kinase 1 (Cdk1), whose activity is regulated directly by mitotic cyclins and phosphatase Cdc25, (Murray, 2004) and indirectly by polo-like kinase 1 (Plk1) (Hansen et al., 2004; Lenart et al., 2007). Plk1, Cdc25, and Cdk1 form a feedback loop and positively regulate each other's activity (Murray, 2004). "
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    Biology Open 02/2012; 1(2):82-91. DOI:10.1242/bio.2011018 · 2.42 Impact Factor
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    • "At the G1/S transition, Emi1 functions as a pseudo-substrate inhibitor of the APC/C (Miller et al., 2006), allowing substrates to accumulate (Guardavaccaro et al., 2003; Miller et al., 2006). In early mitosis , Emi1 is phosphorylated by Plk1 (Hansen et al., 2004), which triggers SCF βTrCP -dependent ubiquitination and destruction, thus inducing APC/C activation and mitotic progression (Margottin- Goguet et al., 2003). Emi1 overexpression leads to unscheduled cell proliferation, tetraploidy, and chromosomal instability in p53- deficient cells (Lehman et al., 2006; Figure 2). "
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    ABSTRACT: The ubiquitin proteasome system (UPS) is required for normal cell proliferation, vertebrate development, and cancer cell transformation. The UPS consists of multiple proteins that work in concert to target a protein for degradation via the 26S proteasome. Chains of an 8.5-kDa protein called ubiquitin are attached to substrates, thus allowing recognition by the 26S proteasome. Enzymes called ubiquitin ligases or E3s mediate specific attachment to substrates. Although there are over 600 different ubiquitin ligases, the Skp1-Cullin-F-box (SCF) complexes and the anaphase promoting complex/cyclosome (APC/C) are the most studied. SCF involvement in cancer has been known for some time while APC/C's cancer role has recently emerged. In this review we will discuss the importance of APC/C to normal cell proliferation and development, underscoring its possible contribution to transformation. We will also examine the hypothesis that modulating a specific interaction of the APC/C may be therapeutically attractive in specific cancer subtypes. Finally, given that the APC/C pathway is relatively new as a cancer target, therapeutic interventions affecting APC/C activity may be beneficial in cancers that are resistant to classical chemotherapy.
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