Polo-box domains confer target specificity to the Polo-like kinase family

Abstract

Polo-like kinases (Plks) contain a conserved Polo-box domain, shown to bind to phosphorylated Ser-pSer/pThr-Pro motifs. The Polo-box domain of Plk-1 mediates substrate interaction and plays an important role in subcellular localization. Intriguingly, the major interactions between the PBD and the optimal recognition peptide are mediated by highly conserved residues in the PBD, suggesting there is little target specificity conveyed by the various PBDs. However, here we show that the affinity of the purified Plk1-3 PBDs to both a physiological Cdc25C derived phospho-peptide and an optimal recognition phospho-peptide differs significantly among family members. To decipher the role of the PBDs and kinase domains in inferring Plk specificity, we exchanged the PBD of Plk1 (PBD1) with the PBD of Plk2, 3, or 4 (PBD2-4). The resulting hybrid proteins can restore bipolar spindle formation and centrosome maturation in Plk1-depleted U2OS cells to various degrees. In these experiments PBD2 was most efficient in complementing PBD-function. Using the MPM2 antibody that recognizes a large set of mitotic phospho-proteins, we could show that PBD1 and PBD2 display some limited overlap in target recognition. Thus, PBDs convey a significant deal of target specificity, indicating that there is only a limited amount of functional redundancy possible within the Plk family.

Plk5, a Polo Box Domain-Only Protein with Specific Roles in Neuron Differentiation and Glioblastoma Suppression

“…Whether the Plk5 PBD recognizes specific substrates or may compete for common partners with other Plk family members is currently unknown. However, the fact that Plk5 lacks relevant residues involved in protein interaction in PBD2 (H538/K450 in Plk1) and the dispensability of the conserved tryptophan in PBD1 suggests that Plk5 may use different mechanisms than those reported for Plk1, as suggested for PLK2 and PLK3 (54).…”

“…5 and 6) and does not contain the kinase domain. The PBD is a relevant domain that confers specificity in partner binding (54). Thus, it is tempting to speculate that Plk5 has evolved as a kinase-deficient protein, where the PBD may function in protein-protein interaction without the subsequent phosphorylation.…”

“…These include the Plk1 subfamily, containing Drosophila polo and mammalian Plk1; the SAK subfamily, containing Drosophila SAK and mammalian Plk4, both of which are widely distributed across the eukaryotes; and the Plk2 subfamily, containing vertebrate Plk2 and Plk3 and also including homologs from echinoderms (4,8,10,35). The PBD participates in subcellular localization and partner interaction (16,54). The founding member of the family, Plk1, localizes to the cytoplasm and centrosomes in interphase and concentrates to the kinetochores and the cytokinesis bridge during cell division.…”

BRCA2 Phosphorylated by PLK1 Moves to the Midbody to Regulate Cytokinesis Mediated by Nonmuscle Myosin IIC

“…Plk1 contains a serine/ threonine kinase domain followed by the carboxy-terminal polo-box domain (PBD), which binds to phosphopeptides within a consensus motif of S-[pS/pT]-[P/X] (15,16). The PBD regulates cellular function, the interaction with substrates, and the subcellular localization of Plk1 (17). Plk1 is also required for appropriate localization of substrates (18).…”

JIP4 is a PLK1 binding protein that regulates p38MAPK activity in G2 phase

“…4 function and substrate specificity of PLK1 is conferred by its Polobox domain (PBD) which binds primarily to mitotic phospho-Ser/Thr residues [17] and confers functional specificity [18,19]. A number of studies have taken a proteomics approach to identify mitotic PLK1 PBD-dependent binding partners and substrates [20,21].…”