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F1000 Biol Rep. 2010; 2: 58.
Published online 2010 August 9. doi:  10.3410/B2-58
PMCID: PMC2990628

Plk4/SAK/ZYG-1 in the regulation of centriole duplication


Centrioles organize both centrosomes and cilia. Centriole duplication is tightly regulated and coordinated with the cell cycle to limit duplication to only once per cell cycle. Defects in centriole number and structure are commonly found in cancer. Plk4/SAK and the functionally related Caenorhabditis elegans ZYG-1 kinases initiate centriole duplication. Several recent studies have elucidated the regulated activity of these kinases and potential downstream targets for centriole assembly.

Introduction and context

Centriole assembly facilitates the formation of two centrosomes with a pair of resident centrioles at their core, providing the basis for bipolar spindle organization during mitosis. Duplication also ensures that each daughter cell receives a pair of centrioles with one old, mother centriole and one new, daughter centriole [1,2].

Centriole biogenesis occurs via a series of conserved morphological stages that culminate in a cylindrical structure that is competent to recruit pericentriolar material for centrosome function and to nucleate cilia (reviewed in [3-7]). The new daughter centriole is first detected as an amorphous electron density and a cartwheel adjacent to the proximal end of the mother centriole. The cartwheel is composed of a central tubule of approximately 25 nm in diameter and nine spokes that extend outward from the central tubule. Triplet microtubules form at the end of each spoke to form the pro-centriole. The pro-centriole then matures into a centriole by additional triplet microtubule growth and the assembly of accessory molecular components and structures.

The coiled-coil protein Sas6 is a conserved component of central tubules that is essential for central tubule and, ultimately, centriole formation [8-14]. In Drosophila, overexpression of Sas6 initiates both central tubule and centriole formation, suggesting that this protein is important for early centriole assembly, and possibly limiting in the process [13,15]. Furthermore, the centriole functions of the cartwheel protein Bld10 [10], and of SAS-4/CPAP (centrosomal P4.1-associated protein), which directs microtubule assembly [16-19], both depend on prior Sas6 function in the pathway. It is this core group of proteins (Sas6, Sas4 and Bld10) that make up a conserved, ancestral module [20,21]. Cartwheels are thought to be dynamic in that they are required to initiate pro-centriole assembly but, in many cell types, are no longer detected in mature centrioles [17,22]. Consistent with the central tubule loss from mature centrioles, Sas6 also disappears with centriole maturation in human cells whereas Sas6 and the central tubule/cartwheel remain at centrioles in Chlamydomonas and Tetrahymena, in which the cartwheel is detected in mature centrioles [10,11,22].

A number of models exist for the licensing and regulation of new centriole assembly (reviewed in [1,2,23]). One conserved mechanism is the regulation of centriole assembly by the Polo-like kinase Plk4/SAK, and the functionally related kinase Caenorhabditis elegans ZYG-1 [20,21,24-26]. Two recent studies have explored the evolution of these protein kinases [20,21]. Here, we review additional studies that begin to uncover the regulation of Plk4/SAK/ZYG-1 and how these kinases may directly activate Sas6.

Major recent advances

Regulating Plk4/SAK/ZYG-1 kinase activity

Plk4/SAK/ZYG-1 localizes to centrioles and centrosomes and is required for normal duplication [24,25,27,28]. Active Plk4/SAK kinase is present at duplicating mother centrioles during G1/S and the protein levels increase at both centrioles into mitosis [29]. In addition to centriole localization, Plk4/SAK protein levels are regulated and, when aberrant, centriole assembly is either amplified or decreased corresponding to levels of Plk4/SAK [30,31]. Defects resulting in either too much or too little Plk4/SAK are deleterious and correlate with chromosome instability (CIN) and cancer [32,33].

Plk4/SAK is a low abundance protein that is SCF/Slimb ubiquitinated and targeted for destruction by the 26S proteosome in Drosophila [34-36]. This destruction limits centrosome/centriole amplification. Importantly, the SCF-mediated destruction of Plk4/SAK is also affected by its autophosphorylation at a phosphodegron motif [37]. Thus, Plk4/SAK self-regulates its activity by phosphorylation to promote its own destruction. In addition to protein destruction, Plk4/SAK phosphorylated in the phosphodegron (S305) is differentially localized to the centrosome pericentriolar material [29]. This may be a mechanism of sequestration to further control the activation of centriole duplication. As Plk4/SAK kinase activity increases, the protein becomes destroyed and re-localized in a self-regulating mechanism to limit centriole re-duplication. Plk4/SAK levels become highest during mitosis. Finally, centrosome levels of C. elegans ZYG-1 are also regulated by the conserved, putative RNA binding protein SZY-20 [38]. Thus, the regulation of Plk4/SAK/ZYG-1 appears to undergo multiple mechanisms of regulated activity, reflecting the tight cell cycle coordination and potentially multiple cellular functions for these kinases.

Capitalizing on the multiple mechanisms for regulating Plk4/SAK/ZYG-1 kinases, variant activity is observed depending on cell type and cell cycle differences. For example, C. elegans ZYG-1 is differentially regulated during mitosis and meiosis via dissimilar localization dependencies and this may reflect both positive and negative mechanisms for ZYG-1 activity in centriole duplication [39].

What are the Plk4/SAK/ZYG-1 kinase substrates?

The target(s) of Plk4/SAK/ZYG-1 phosphorylation for centriole assembly is not well understood. However, ZYG-1 was recently found to phosphorylate SAS-6 at Ser123 in C. elegans [40]. Ser123 is not a conserved residue in the Sas6 protein family, suggesting that the site of regulation is divergent, as are the kinases controlling centriole duplication. Consistent with conservation in the regulatory mechanism, however, HsSas6 localization is, in part, regulated by Plk4 [22].

SAS-6 mutations that mimic the phosphorylation (S123D) can restore centriole duplication in a partial ZYG-1 knockdown [40] that would normally arrest cells with monopolar spindles due to inhibition of centriole duplication [28]. Despite its ability to compensate for a partial loss of ZYG-1 function, the phospho-mimetic SAS-6 mutant cannot rescue the complete loss of ZYG-1, indicating that ZYG-1 has other roles in promoting centriole duplication.

SAS-6 S123 phosphorylation is required for normal SAS-6 maintenance at centrioles [40]. The protein localization dynamics suggest a model in which SAS-6 phosphorylation is not required for recruitment to centrioles but S123 phosphorylation is required to maintain SAS-6 at centrioles later in the cell cycle. This is consistent with human studies where Plk4 is required to maintain Sas6 at centrioles during mitosis and less so during interphase [22].

Future directions

The coordination of centriole assembly with the cell cycle is critical for regulated spindle assembly. A series of recent studies describing the regulation and a downstream target of Plk4/SAK/ZYG-1 protein kinases has begun to describe the complexity of this process.

Perhaps the most intriguing feature of these studies is the observation that Plk4/SAK activity peaks at mitosis and promotes maintenance of Sas6 during this same time in the cell cycle. While both of these proteins are clearly important to initiate centriole assembly, multiple functions are revealed by these studies. An added layer of complexity also comes from the differences between ZYG-1 regulation in mitotic and meiotic cells [39]. In addition to its role in centriole function, Plk4’s cell division role is likely to be more complex, with key functions in cytokinesis. Plk4 may regulate Rho GTPase and cytokinesis by phosphorylating the Rho guanine nucleotide exchange factor Ect2 [41]. Altered Plk4 activity may also drive carcinogenesis by disrupting Plk4’s cytokinesis function [41,42].

Finally, the phosphorylated and unphosphorylated forms of Sas6 may have unique properties to facilitate both central tubule assembly and other functions that remain to be discovered. New central tubule formation for the initiating stages appears to not require Sas6 phosphorylation. Along these lines, such modification may negatively regulate the Sas6 oligomerization that can generate tubule formation in vitro [43]. The differential phospho-Sas6 may be required for centriole maturation to form a stable structure. Beyond its regulation are questions concerning how Sas6 contributes to central tubule formation and the creation of ninefold radial symmetry in attachment of the cartwheel spokes to the central tubule.


The authors express thanks to all three reviewers for helpful comments and criticisms. This work was funded by the National Institutes of Health (GM074746) and the March of Dimes Birth Defects Foundation (1-FY07-520) to MW.


polo-like kinase 4
Snk/Plk-akin kinase
spindle assembly abnormal protein 6 homolog
Skp, Cullin, F-box containing complex


The electronic version of this article is the complete one and can be found at:


Competing Interests

The authors declare that they have no competing interests.


1. Nigg EA, Raff JW. Centrioles, centrosomes, and cilia in health and disease. Cell. 2009;139:663–78. [PubMed]
2. Debec A, Sullivan W, Bettencourt-Dias M. Centrioles: active players or passengers during mitosis? Cell Mol Life Sci. 2010;67:2173–94. doi: 10.1007/s00018-010-0323-9. [PMC free article] [PubMed] [Cross Ref]
3. Delattre M, Gonczy P. The arithmetic of centrosome biogenesis. J Cell Sci. 2004;117:1619–30. doi: 10.1242/jcs.01128. [PubMed] [Cross Ref]
4. Pearson CG, Winey M. Basal body assembly in ciliates: the power of numbers. Traffic. 2009;10:461–71. doi: 10.1111/j.1600-0854.2009.00885.x. [PMC free article] [PubMed] [Cross Ref]
5. Dutcher SK. Finding treasures in frozen cells: new centriole intermediates. Bioessays. 2007;29:630–4. doi: 10.1002/bies.20594. [PubMed] [Cross Ref]
6. Bettencourt-Dias M, Glover DM. Centrosome biogenesis and function: centrosomics brings new understanding. Nat Rev Mol Cell Biol. 2007;8:451–63. doi: 10.1038/nrm2180. [PubMed] [Cross Ref]
7. Strnad P, Gonczy P. Mechanisms of procentriole formation. Trends Cell Biol. 2008;18:389–96. doi: 10.1016/j.tcb.2008.06.004. [PubMed] [Cross Ref]
8. Dammermann A, Muller-Reichert T, Pelletier L, Habermann B, Desai A, Oegema K. Centriole assembly requires both centriolar and pericentriolar material proteins. Dev Cell. 2004;7:815–29. doi: 10.1016/j.devcel.2004.10.015. [PubMed] [Cross Ref] F1000 Factor 6.0 Must Read
Evaluated by Conly Rieder 14 Dec 2004
9. Leidel S, Delattre M, Cerutti L, Baumer K, Gonczy P. SAS-6 defines a protein family required for centrosome duplication in C. elegans and in human cells. Nat Cell Biol. 2005;7:115–25. doi: 10.1038/ncb1220. [PubMed] [Cross Ref]
10. Nakazawa Y, Hiraki M, Kamiya R, Hirono M. SAS-6 is a cartwheel protein that establishes the 9-fold symmetry of the centriole. Curr Biol. 2007;17:2169–74. doi: 10.1016/j.cub.2007.11.046. [PubMed] [Cross Ref]
11. Culver BP, Meehl JB, Giddings TH Jr, Winey M. The two SAS-6 homologs in Tetrahymena thermophila have distinct functions in basal body assembly. Mol Biol Cell. 2009;20:1865–77. doi: 10.1091/mbc.E08-08-0838. [PMC free article] [PubMed] [Cross Ref]
12. Vladar EK, Stearns T. Molecular characterization of centriole assembly in ciliated epithelial cells. J Cell Biol. 2007;178:31–42. doi: 10.1083/jcb.200703064. [PMC free article] [PubMed] [Cross Ref]
13. Rodrigues-Martins A, Bettencourt-Dias M, Riparbelli M, Ferreira C, Ferreira I, Callaini G, Glover DM. DSAS-6 organizes a tube-like centriole precursor, and its absence suggests modularity in centriole assembly. Curr Biol. 2007;17:1465–72. doi: 10.1016/j.cub.2007.07.034. [PubMed] [Cross Ref]
14. Kilburn CL, Pearson CG, Romijn EP, Meehl JB, Giddings TH, Jr, Culver BP, Yates JR 3rd, Winey M. New Tetrahymena basal body protein components identify basal body domain structure. J Cell Biol. 2007;178:905–12. doi: 10.1083/jcb.200703109. [PMC free article] [PubMed] [Cross Ref]
15. Peel N, Stevens NR, Basto R, Raff JW. Overexpressing centriole-replication proteins in vivo induces centriole overduplication and de novo formation. Curr Biol. 2007;17:834–43. doi: 10.1016/j.cub.2007.04.036. [PMC free article] [PubMed] [Cross Ref]
16. Delattre M, Canard C, Gonczy P. Sequential protein recruitment in C. elegans centriole formation. Curr Biol. 2006;16:1844–9. doi: 10.1016/j.cub.2006.07.059. [PubMed] [Cross Ref]
17. Pelletier L, O'Toole E, Schwager A, Hyman AA, Muller-Reichert T. Centriole assembly in Caenorhabditis elegans. Nature. 2006;444:619–23. doi: 10.1038/nature05318. [PubMed] [Cross Ref] F1000 Factor 6.5 Must Read
Evaluated by Stephen Doxsey 07 Dec 2006, Bodo Lange 14 Dec 2006, Berl R Oakley 15 Dec 2006
18. Dammermann A, Maddox PS, Desai A, Oegema K. SAS-4 is recruited to a dynamic structure in newly forming centrioles that is stabilized by the gamma-tubulin-mediated addition of centriolar microtubules. J Cell Biol. 2008;180:771–85. doi: 10.1083/jcb.200709102. [PMC free article] [PubMed] [Cross Ref]
19. Kohlmaier G, Loncarek J, Meng X, McEwen BF, Mogensen MM, Spektor A, Dynlacht BD, Khodjakov A, Gonczy P. Overly long centrioles and defective cell division upon excess of the SAS-4-related protein CPAP. Curr Biol. 2009;19:1012–8. doi: 10.1016/j.cub.2009.05.018. [PMC free article] [PubMed] [Cross Ref] F1000 Factor 3.2 Recommended
Evaluated by Greenfield Sluder 17 Aug 2009, David Pellman 03 Sep 2009
20. Carvalho-Santos Z, Machado P, Branco P, Tavares-Cadete F, Rodrigues-Martins A, Pereira-Leal JB, Bettencourt-Dias M. Stepwise evolution of the centriole-assembly pathway. J Cell Sci. 2010;123:1414–26. doi: 10.1242/jcs.064931. [PubMed] [Cross Ref]
21. Hodges ME, Scheumann N, Wickstead B, Langdale JA, Gull K. Reconstructing the evolutionary history of the centriole from protein components. J Cell Sci. 2010;123:1407–13. doi: 10.1242/jcs.064873. [PubMed] [Cross Ref]
22. Strnad P, Leidel S, Vinogradova T, Euteneuer U, Khodjakov A, Gonczy P. Regulated HsSAS-6 levels ensure formation of a single procentriole per centriole during the centrosome duplication cycle. Dev Cell. 2007;13:203–13. doi: 10.1016/j.devcel.2007.07.004. [PMC free article] [PubMed] [Cross Ref]
23. Nigg EA. Centrosome duplication: of rules and licenses. Trends Cell Biol. 2007;17:215–21. doi: 10.1016/j.tcb.2007.03.003. [PubMed] [Cross Ref]
24. Bettencourt-Dias M, Rodrigues-Martins A, Carpenter L, Riparbelli M, Lehmann L, Gatt MK, Carmo N, Balloux F, Callaini G, Glover DM. SAK/PLK4 is required for centriole duplication and flagella development. Curr Biol. 2005;15:2199–207. doi: 10.1016/j.cub.2005.11.042. [PubMed] [Cross Ref]
25. Habedanck R, Stierhof YD, Wilkinson CJ, Nigg EA. The Polo kinase Plk4 functions in centriole duplication. Nat Cell Biol. 2005;7:1140–6. doi: 10.1038/ncb1320. [PubMed] [Cross Ref]
26. O’Connell KF. The ZYG-1 kinase, a mitotic and meiotic regulator of centriole replication. Oncogene. 2002;21:6201–8. doi: 10.1038/sj.onc.1205776. [PubMed] [Cross Ref]
27. Kleylein-Sohn J, Westendorf J, Le Clech M, Habedanck R, Stierhof Y-D, Nigg EA. Plk4-induced centriole biogenesis in human cells. Dev Cell. 2007;13:190–202. doi: 10.1016/j.devcel.2007.07.002. [PubMed] [Cross Ref]
28. O’Connell KF, Caron C, Kopish KR, Hurd DD, Kemphues KJ, Li Y, White JG. The C. elegans zyg-1 gene encodes a regulator of centrosome duplication with distinct maternal and paternal roles in the embryo. Cell. 2001;105:547–58. [PubMed] F1000 Factor 3.0 Recommended
Evaluated by Robert K Herman 11 Jan 2002
29. Sillibourne JE, Tack F, Vloemans N, Boeckx A, Thambirajah S, Bonnet P, Ramaekers FC, Bornens M, Grand-Perret T. Autophosphorylation of polo-like kinase 4 and its role in centriole duplication. Mol Biol Cell. 2010;21:547–61. doi: 10.1091/mbc.E09-06-0505. [PMC free article] [PubMed] [Cross Ref]
30. Duensing A, Spardy N, Chatterjee P, Zheng L, Parry J, Cuevas R, Korzeniewski N, Duensing S. Centrosome overduplication, chromosomal instability, and human papillomavirus oncoproteins. Environ Mol Mutagen. 2009;50:741–7. doi: 10.1002/em.20478. [PubMed] [Cross Ref]
31. Kuriyama R, Bettencourt-Dias M, Hoffmann I, Arnold M, Sandvig L. Gamma-tubulin-containing abnormal centrioles are induced by insufficient Plk4 in human HCT116 colorectal cancer cells. J Cell Sci. 2009;122:2014–23. doi: 10.1242/jcs.036715. [PubMed] [Cross Ref]
32. Swallow CJ, Ko MA, Siddiqui NU, Hudson JW, Dennis JW. Sak/Plk4 and mitotic fidelity. Oncogene. 2005;24:306–12. doi: 10.1038/sj.onc.1208275. [PubMed] [Cross Ref]
33. Macmillan JC, Hudson JW, Bull S, Dennis JW, Swallow CJ. Comparative expression of the mitotic regulators SAK and PLK in colorectal cancer. Ann Surg Oncol. 2001;8:729–40. doi: 10.1007/s10434-001-0729-6. [PubMed] [Cross Ref]
34. Cunha-Ferreira I, Rodrigues-Martins A, Bento I, Riparbelli M, Zhang W, Laue E, Callaini G, Glover DM, Bettencourt-Dias M. The SCF/Slimb ubiquitin ligase limits centrosome amplification through degradation of SAK/PLK4. Curr Biol. 2009;19:43–9. doi: 10.1016/j.cub.2008.11.037. [PubMed] [Cross Ref]
35. Rogers GC, Rusan NM, Roberts DM, Peifer M, Rogers SL. The SCF Slimb ubiquitin ligase regulates Plk4/Sak levels to block centriole reduplication. J Cell Biol. 2009;184:225–39. doi: 10.1083/jcb.200808049. [PMC free article] [PubMed] [Cross Ref]
36. Korzeniewski N, Zheng L, Cuevas R, Parry J, Chatterjee P, Anderton B, Duensing A, Munger K, Duensing S. Cullin 1 functions as a centrosomal suppressor of centriole multiplication by regulating polo-like kinase 4 protein levels. Cancer Res. 2009;69:6668–75. doi: 10.1158/0008-5472.CAN-09-1284. [PMC free article] [PubMed] [Cross Ref]
37. Holland AJ, Lan W, Niessen S, Hoover H, Cleveland DW. Polo-like kinase 4 kinase activity limits centrosome overduplication by autoregulating its own stability. J Cell Biol. 2010;188:191–8. doi: 10.1083/jcb.200911102. [PMC free article] [PubMed] [Cross Ref] F1000 Factor 3.0 Recommended
Evaluated by William Earnshaw 17 Feb 2010
38. Song MH, Aravind L, Muller-Reichert T, O’Connell KF. The conserved protein SZY-20 opposes the Plk4-related kinase ZYG-1 to limit centrosome size. Dev Cell. 2008;15:901–12. doi: 10.1016/j.devcel.2008.09.018. [PMC free article] [PubMed] [Cross Ref]
39. Peters N, Perez DE, Song MH, Liu Y, Muller-Reichert T, Caron C, Kemphues KJ, O’Connell KF. Control of mitotic and meiotic centriole duplication by the Plk4-related kinase ZYG-1. J Cell Sci. 2010;123:795–805. doi: 10.1242/jcs.050682. [PubMed] [Cross Ref]
40. Kitagawa D, Busso C, Fluckiger I, Gonczy P. Phosphorylation of SAS-6 by ZYG-1 is critical for centriole formation in C. elegans embryos. Dev Cell. 2009;17:900–7. doi: 10.1016/j.devcel.2009.11.002. [PubMed] [Cross Ref] F1000 Factor 6.0 Must Read
Evaluated by Mark Winey 27 Jan 2010
41. Rosario CO, Ko MA, Haffani YZ, Gladdy RA, Paderova J, Pollett A, Squire JA, Dennis JW, Swallow CJ. Plk4 is required for cytokinesis and maintenance of chromosomal stability. Proc Natl Acad Sci U S A. 2010;107:6888–93. doi: 10.1073/pnas.0910941107. [PubMed] [Cross Ref]
42. Bettencourt-Dias M, Giet R, Sinka R, Mazumdar A, Lock WG, Balloux F, Zafiropoulos PJ, Yamaguchi S, Winter S, Carthew RW, Cooper M, Jones D, Frenz L, Glover DM. Genome-wide survey of protein kinases required for cell cycle progression. Nature. 2004;432:980–7. doi: 10.1038/nature03160. [PubMed] [Cross Ref] F1000 Factor 6.8 Must Read
Evaluated by Michael B Yaffe 04 Jan 2005, Iain Hagan 14 Jan 2005, Ulf Pettersson 26 Jan 2005, Bodo Lange 14 Feb 2005
43. Gopalakrishnan J, Guichard P, Smith AH, Schwarz H, Agard DA, Marco S, Avidor-Reiss T. Self-assembling SAS-6 multimer is a core centriole building block. J Biol Chem. 2010;285:8759–70. doi: 10.1074/jbc.M109.092627. [PMC free article] [PubMed] [Cross Ref]

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