Cell cycle-dependent expression of gamma-tubulin in the amicronuclear ciliate Tetrahymena pyriformis.
In ciliates, different microtubular structures are nucleated from diverse Microtubule Organizing Centers (MTOCs). gamma-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 gamma-tubulin on different MTOCs and during the cell cycle. In Tetrahymena thermophila, the alpha- and beta-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 alpha- and beta-tubulin transcription. This study deals with the characterization of gamma-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 gamma-tubulin molecule. gamma-Tubulin expression during the cell cycle, in the presence of microtubular poisons and after deciliation, was also characterized. We found that gamma-tubulin mRNA levels are correlated with basal body proliferation and gamma-tubulin nuclear localization. We also found that gamma-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 gamma-tubulin transcription.
Joachimiak
Ewa
E
Department of Molecular, Cellular and Animal Biology, University of Camerino, Camerino 62032, v. Camerini 2, Italy.
Pucciarelli
Sandra
S
Barchetta
Sabrina
S
Ballarini
Patrizia
P
Kaczanowska
Janina
J
Miceli
Cristina
C
D000818:Animals; D002453:Cell Cycle; D016054:DNA, Protozoan / Q000032:analysis; D005786:Gene Expression Regulation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D017422:Sequence Analysis, DNA; D013769:Tetrahymena pyriformis / Q000166:cytology* / Q000378:metabolism; D014404:Tubulin / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
D016054:DNA, Protozoan; D015800:Protozoan Proteins; D014404:Tubulin