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Gene Review

PLK4  -  polo-like kinase 4

Homo sapiens

Synonyms: MCCRP2, PLK-4, Polo-like kinase 4, SAK, STK18, ...
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Disease relevance of PLK4


High impact information on PLK4

  • The majority of spermatids in SAK mutants lack centrioles and so are unable to make sperm axonemes [3].
  • Human cells depleted of SAK show error-prone mitosis, likely to underlie its tumor-suppressor role [3].
  • RESULTS: Here, we show that downregulation of SAK in Drosophila cells, by mutation or RNAi, leads to loss of centrioles, the core structures of centrosomes [3].
  • SAK-/- mice die during embryogenesis, whereas SAK+/- mice develop liver and lung tumors and SAK+/- MEFs show mitotic abnormalities [3].
  • We also show that SAK mutants lose their centrioles during the mitotic divisions preceding male meiosis but still produce cysts of 16 primary spermatocytes as in the wild-type [3].

Biological context of PLK4

  • Although Sak protein is presumed to be involved in cell growth mechanism, efforts have failed to demonstrate its kinase activity [4].
  • Little has been, therefore, elucidated how Sak is regulated and how Sak contributes to cell proliferation [4].
  • SAK, a new polo-like kinase, is transcriptionally repressed by p53 and induces apoptosis upon RNAi silencing [5].
  • Using in vitro kinase assays on peptide spots arrays, we determined the consensus phosphorylation motif for Sak to be yen-[Ile/Leu/Val]-Ser/Thr-varphi-varphi-X- yen/Pro (where varphi denotes a large hydrophobic residue, yen is a charged residue dependent on the context of the surrounding sequence, and residues in brackets are unfavoured) [6].
  • The predicted protein sequences of Rab7a and Rab7b contain all characteristic domains essential for Rab function: the effector domain (YRATVGADF) and four GTP-binding consensus sequences (GDSGVGKT, WDTAGQ, NKLD, SAK) as well as the prenylation motif (-CC) at the C-terminus indispensable for Rab binding to the membrane [7].

Anatomical context of PLK4

  • Finally, we show that depletion of SAK in human cells also prevents centriole duplication and gives rise to mitotic abnormalities [3].
  • Levels of SAK and PLK expression in tumor relative to paired normal mucosa correlated directly with patient age and with each other but did not correlate with tumor stage [2].
  • RESULTS: In the majority of cases, both SAK and PLK were more highly expressed in tumor tissue than in adjacent normal intestinal mucosa [2].

Associations of PLK4 with chemical compounds

  • SAK and PLK are members of the polo family of serine threonine kinases, which in lower organisms have been shown to be required for the precise regulation of mitosis [2].
  • CD spectra of polycationic (SAK, OAK), amphoteric (EAK), or polyanionic (Ac-EAK) polylysine derivatives were recorded in 0.25M acetate buffer at pH 7.4 as well as in the presence of DPPC or DPPC/PG (95/5, 80/20 mol/mol) liposomes [8].

Regulatory relationships of PLK4

  • Further characterization revealed that SAK expression was downregulated by wild-type p53 in several tumor cell models [5].

Other interactions of PLK4


Analytical, diagnostic and therapeutic context of PLK4

  • The intensity of ELISA reaction was highest against the recombinant fusion antigen GSTBP22; the chemically conjugated SAK-BP22 performed less well than the free dimeric form of the peptide [9].


  1. Extensive phage dynamics in Staphylococcus aureus contributes to adaptation to the human host during infection. Goerke, C., Wirtz, C., Flückiger, U., Wolz, C. Mol. Microbiol. (2006) [Pubmed]
  2. Comparative expression of the mitotic regulators SAK and PLK in colorectal cancer. Macmillan, J.C., Hudson, J.W., Bull, S., Dennis, J.W., Swallow, C.J. Ann. Surg. Oncol. (2001) [Pubmed]
  3. SAK/PLK4 is required for centriole duplication and flagella development. Bettencourt-Dias, M., Rodrigues-Martins, A., Carpenter, L., Riparbelli, M., Lehmann, L., Gatt, M.K., Carmo, N., Balloux, F., Callaini, G., Glover, D.M. Curr. Biol. (2005) [Pubmed]
  4. Sak serine-threonine kinase acts as an effector of Tec tyrosine kinase. Yamashita, Y., Kajigaya, S., Yoshida, K., Ueno, S., Ota, J., Ohmine, K., Ueda, M., Miyazato, A., Ohya, K., Kitamura, T., Ozawa, K., Mano, H. J. Biol. Chem. (2001) [Pubmed]
  5. SAK, a new polo-like kinase, is transcriptionally repressed by p53 and induces apoptosis upon RNAi silencing. Li, J., Tan, M., Li, L., Pamarthy, D., Lawrence, T.S., Sun, Y. Neoplasia (2005) [Pubmed]
  6. Determination of the Plk4/Sak consensus phosphorylation motif using peptide spots arrays. Leung, G.C., Ho, C.S., Blasutig, I.M., Murphy, J.M., Sicheri, F. FEBS Lett. (2007) [Pubmed]
  7. Cloning of two genes encoding Rab7 in Paramecium. Surmacz, L., Wiejak, J., Wyroba, E. Acta Biochim. Pol. (2006) [Pubmed]
  8. Effect of phospholipid bilayers on solution conformation of branched polymeric polypeptides and peptide-polymer conjugates. Nagy, I.B., Majer, Z., Hudecz, F. Biopolymers (2001) [Pubmed]
  9. Modeling of main characteristics of bullous pemphigoid antigen-2 (BPAG2) peptide structure in serological recognition by autoantibodies. Pál, J., Marczinovits, I., Hudecz, F., Tóth, G.K., Mezõ, G., Molnár, J., Németh, P. Pathol. Oncol. Res. (2004) [Pubmed]
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