Background: The eukaryotic cytosolic chaperonin CCT is a hetero-oligomeric complex formed by two rings connected back-to-back, each composed of eight distinct subunits (CCTα to CCTζ). CCT complex mediates the folding, of a wide range of newly synthesised proteins including tubulin (α, β and γ) and actin, as quantitatively major substrates. Methodology/Principal Findings: We disrupted the genes encoding CCTα and CCTδ subunits in the ciliate Tetrahymena. Cells lacking the zygotic expression of either CCTα or CCTδ showed a loss of cell body microtubules, failed to assemble new cilia and died within 2 cell cycles. We also show that loss of CCT subunit activity leads to axoneme shortening and splaying of tips of axonemal microtubules. An epitope-tagged CCTα rescued the gene knockout phenotype and localized primarily to the tips of cilia. A mutation in CCTα, G346E, at a residue also present in the related protein implicated in the Bardet Biedel Syndrome, BBS6, also caused defects in cilia and impaired CCTα localization in cilia. Conclusions/Significance: Our results demonstrate that the CCT subunits are essential and required for ciliary assembly and maintenance of axoneme structure, especially at the tips of cilia.
Seixas, C., Cruto, T., Tavares, A., Gaertig, J., & Soares, H. (2010). CCTα and CCTδ chaperonin subunits are essential and required for cilia assembly and maintenance in Tetrahymena. PLoS ONE, 5(5). https://doi.org/10.1371/journal.pone.0010704