Abstract
Polo-like kinases (Plks) are evolutionarily conserved serine/threonine protein kinases playing crucial roles during multiple stages of mitosis and cytokinesis in yeast and animals. Plks are characterized by a unique Polo-box domain, which plays regulatory roles in controlling Plk activation, interacting with substrates and targeting Plk to specific subcellular locations. Plk activity and protein abundance are subject to temporal and spatial control through transcription, phosphorylation and proteolysis. In the early branching protists, Plk orthologues are present in some taxa, such as kinetoplastids and Giardia, but are lost in apicomplexans, such as Plasmodium. Works from characterizing a Plk orthologue in Trypanosoma brucei, a kinetoplastid protozoan, discover its essential roles in regulating the inheritance of flagellum-associated cytoskeleton and the initiation of cytokinesis, but not any stage of mitosis. These studies reveal evolutionarily conserved and species-specific features in the control of Plk activation, substrate recognition and protein abundance, and suggest the divergence of Plk function and regulation for specialized needs in this flagellated unicellular eukaryote.
Highlights
The Polo kinase was originally discovered in Drosophila melanogaster more than 30 years ago and named after the phenotype of abnormal spindle poles in a mitotic mutant [1,2]
The essential involvement of T. brucei Polo-like kinase (Plk) orthologue (TbPLK) in regulating the inheritance of multiple flagellum-associated cytoskeletal structures, including the basal body, the hook complex and the flagellum attachment zone (FAZ), suggests a divergent function for this evolutionarily conserved protein kinase in a protozoan parasite that relies on the flagellum for locomotion, cell morphogenesis, cell division and cell–cell communication
Duplication and segregation of the basal body are among the earliest events in the cell cycle of T. brucei, and the implication of TbPLK in the process of basal body segregation reflects the conserved function of Plks in the duplication and maturation of centrioles in animals and spindle pole bodies in yeast
Summary
The Polo kinase was originally discovered in Drosophila melanogaster more than 30 years ago and named after the phenotype of abnormal spindle poles in a mitotic mutant [1,2]. Polo kinase and its orthologues in other eukaryotic organisms have been established as central regulators of the cell cycle, playing crucial roles in various stages of mitosis and cytokinesis [3,4]. The eukaryotic organisms with increased complexity of the cell cycle usually contain more Polo-like kinase (Plk) paralogues. The unicellular fungi, such as royalsocietypublishing.org/journal/rsob Open Biol. The unicellular fungi, such as royalsocietypublishing.org/journal/rsob Open Biol. 10: 200189
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