The two SAS-6 homologs in Tetrahymena thermophila have distinct functions in basal body assembly

Brady P. Culver, Janet B. Meehl, Thomas H. Giddings, Mark Winey

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Cilia and flagella are structurally and functionally conserved organelles present in basal as well as higher eukaryotes. The assembly of cilia requires a microtubule based scaffold called a basal body. The ninefold symmetry characteristic of basal bodies and the structurally similar centriole is organized around a hub and spoke structure termed the cartwheel. To date, SAS-6 is one of the two clearly conserved components of the cartwheel. In some organisms, overexpression of SAS-6 causes the formation of supernumerary centrioles. We questioned whether the centriole assembly initiation capacity of SAS-6 is separate from or directly related to its structural role at the cartwheel. To address this question we used Tetrahymena thermophila, which expresses two SAS-6 homologues, TtSAS6a and TtSAS6b. Cells lacking either TtSAS6a or TtSAS6b are defective in new basal body assembly. TtSas6a localizes to all basal bodies equally, whereas TtSas6b is enriched at unciliated and assembling basal bodies. Interestingly, overexpression of TtSAS6b but not TtSAS6a, led to the assembly of clusters of new basal bodies in abnormal locations. Our data suggest a model where TtSAS6a and TtSAS6b have diverged such that TtSAS6a acts as a structural component of basal bodies, whereas TtSAS6b influences the location of new basal body assembly.

Original languageEnglish (US)
Pages (from-to)1855-1864
Number of pages10
JournalMolecular Biology of the Cell
Issue number6
StatePublished - Mar 15 2009
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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