title: The Centriole Cartwheel Protein SAS-6 in Trypanosoma brucei Is Required for Probasal Body Biogenesis and Flagellum Assembly.
abstract: The centriole in eukaryotes functions as the cell's microtubule-organizing center (MTOC) to nucleate spindle assembly, and its biogenesis requires an evolutionarily conserved protein, SAS-6, which assembles the centriole cartwheel. Trypanosoma brucei, an early branching protozoan, possesses the basal body as its MTOC to nucleate flagellum biogenesis. However, little is known about the components of the basal body and their roles in basal body biogenesis and flagellum assembly. Here, we report that the T. brucei SAS-6 homolog, TbSAS-6, is localized to the mature basal body and the probasal body throughout the cell cycle. RNA interference (RNAi) of TbSAS-6 inhibited probasal body biogenesis, compromised flagellum assembly, and caused cytokinesis arrest. Surprisingly, overexpression of TbSAS-6 in T. brucei also impaired probasal body duplication and flagellum assembly, contrary to SAS-6 overexpression in humans, which produces supernumerary centrioles. Furthermore, we showed that depletion of T. brucei Polo-like kinase, TbPLK, or inhibition of TbPLK activity did not abolish TbSAS-6 localization to the basal body, in contrast to the essential role of Polo-like kinase in recruiting SAS-6 to centrioles in animals. Altogether, these results identified the essential role of TbSAS-6 in probasal body biogenesis and flagellum assembly and suggest the presence of a TbPLK-independent pathway governing basal body duplication in T. brucei.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Huiqing
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Siegel
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA Ziyin.Li@uth.tmc.edu.
authors.forename: Ziyin
authors.initials: Z
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D064652:Basal Bodies / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D015800:Protozoan Proteins; D017346:Protein Serine-Threonine Kinases