The SCF–FBXW5 E3-ubiquitin ligase is regulated by PLK4 and targets HsSAS-6 to control centrosome duplication

Abstract

Deregulated centrosome duplication can result in genetic instability and contribute to tumorigenesis. Here, we show that centrosome duplication is regulated by the activity of an E3-ubiquitin ligase that employs the F-box protein FBXW5 (ref. 3) as its targeting subunit. Depletion of endogenous FBXW5 or overexpression of an F-box-deleted mutant version results in centrosome overduplication and formation of multipolar spindles. We identify the centriolar protein HsSAS-6 (refs 4,5) as a critical substrate of the SCF-FBXW5 complex. FBXW5 binds HsSAS-6 and promotes its ubiquitylation in vivo. The activity of SCF-FBXW5 is in turn negatively regulated by Polo-like kinase 4 (PLK4), which phosphorylates FBXW5 at Ser 151 to suppress its ability to ubiquitylate HsSAS-6. FBXW5 is a cell-cycle-regulated protein with expression levels peaking at the G1/S transition. We show that FBXW5 levels are controlled by the anaphase-promoting (APC/C) complex, which targets FBXW5 for degradation during mitosis and G1, thereby helping to reset the centrosome duplication machinery. In summary, we show that a cell-cycle-regulated SCF complex is regulated by the kinase PLK4, and that this in turn restricts centrosome re-duplication through degradation of the centriolar protein HsSAS-6.

The Centrosome and Its Duplication Cycle

“…Similar reductions occur for CPAP, STIL, and human Sas-6 and each of these molecules is targeted by APC/C-Cdh1 or Cdc20 (Strnad et al 2007;Tang et al 2009Tang et al , 2011Puklowski et al 2011;Arquint et al 2012;Arquint and Nigg 2014). Interplay between APC/C and SCF pathways has also been reported to regulate levels of Sas-6 (Puklowski et al 2011). Sas-6 forms a complex with Fbxw5 to target its destruction.…”

CRL4A-FBXW5–mediated degradation of DLC1 Rho GTPase-activating protein tumor suppressor promotes non-small cell lung cancer cell growth

“…In addition to CUL4-DDB1, FBXW5 has also been shown to act as a substrate receptor for the CUL1-SKP1 E3 ubiquitin ligase complex, targeting HsSAS-6 or Eps8 for ubiquitination and degradation, to regulate centrosome duplication or mitotic progression, respectively (34,35). In contrast, FBXW5 through CUL4-DDB1 promotes sumoylation rather than ubiquitination of the Myb transcription factor, to alter its nuclear localization and transcriptional activity (39).…”

“…4 C and D). FBXW5 has also been shown to act as a substrate receptor for the SCF (SKPCullin-F box) ubiquitin ligase complex, targeting HsSAS-6 or Eps8 for ubiquitination and degradation, to regulate centrosome duplication or mitotic progression, respectively (34,35). Thus, FBXW5 may have functions independent of DLC1 in NSCLC.…”

The Mechanism of Dynein Light Chain LC8-mediated Oligomerization of the Ana2 Centriole Duplication Factor

“…The Ana2 pep2 binding isotherm was also exothermic and yielded an experimentally determined LC8 K D value of 12.8 Ϯ 1.5 M (Fig. 2B), a weaker binding affinity than (50,51), where it phosphorylates both a known and unknown set of substrates in the centriole duplication pathway (7,52). Sas-6 (spindle assembly abnormal-6) oligomerizes to form the first structure observed using electron microscopy; this nine-spoked cartwheel is depicted on the left.…”