Cell Cycle-dependent Expression of γ-Tubulin in the Amicronuclear Ciliate Tetrahymena pyriformis

• Published in: Protist 2007-01, Vol.158 (1), p.39-50
• Main Authors: Joachimiak, Ewa, Pucciarelli, Sandra, Barchetta, Sabrina, Ballarini, Patrizia, Kaczanowska, Janina, Miceli, Cristina
• Format: Article
• Language: English
• Subjects: Animals; Cell Cycle; cytoskeleton; DNA, Protozoan - analysis; Gene Expression Regulation; microtubules; Models, Molecular; Molecular Sequence Data; Protozoan Proteins - biosynthesis; Protozoan Proteins - chemistry; Protozoan Proteins - genetics; Sequence Analysis, DNA; Tetrahymena pyriformis; Tetrahymena pyriformis - cytology; Tetrahymena pyriformis - metabolism; Tetrahymena thermophila; tubulin; Tubulin - biosynthesis; Tubulin - chemistry; Tubulin - genetics
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1016/j.protis.2006.08.001

In ciliates, different microtubular structures are nucleated from diverse Microtubule Organizing Centers (MTOCs). γ-Tubulin is a tubulin superfamily member that plays an essential role in microtubule nucleation at the MTOCs. However, little is known about mechanisms regulating the activity of γ-tubulin on different MTOCs and during the cell cycle. In Tetrahymena thermophila, the α- and β-tubulin expression is regulated mainly at the transcriptional level, and changes in the ratio of polymerized/unpolymerized tubulin dimers lead to an increase or decrease of α- and β-tubulin transcription. This study deals with the characterization of γ-tubulin in the amicronuclear ciliate Tetrahymena pyriformis. Sequence analysis revealed some specific substitutions in nucleotide-binding loops characteristic of the Tetrahymena genus and putative conserved phosphorylation sites located on the external surface of the γ-tubulin molecule. γ-Tubulin expression during the cell cycle, in the presence of microtubular poisons and after deciliation, was also characterized. We found that γ-tubulin mRNA levels are correlated with basal body proliferation and γ-tubulin nuclear localization. We also found that γ-tubulin expression changes during anti-microtubular drugs treatment, but does not changes during reciliation. These findings suggest a relationship between the level of unpolymerized tubulin dimers and γ-tubulin transcription.