Two functional alpha-tubulin genes of the yeast Saccharomyces cerevisiae encode divergent proteins.

Abstract

Two a-tubulin genes from the budding yeast Saccharomyces cerevisiae were identified and cloned by cross-species DNA homology. Nucleotide sequencing studies revealed that the two genes, named TUB) and TUB3, encoded gene products of 447 and 445 amino acids, respectively, that are highly homologous to oe-tubulins from other species. Comparison of the sequences of the two genes revealed a 19% divergence between the nucleotide sequences and a 10% divergence between the amino acid sequences. Each gene had a single intervening sequence, located at an identical position in codon 9. Cell fractionation studies showed that both gene products were present in yeast microtubules. These two genes, along with the TUB2 1-tubulin gene, probably encode the entire complement of tubulin in budding yeast cells.The process of cell division has been studied extensively in the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. A particularly useful technique has been the isolation of conditional lethal mutants that arrest at specific morphological stages of the cell cycle (23,35,38,39,47,56,70). The normal function of the mutant gene product in such cell cycle mutants has, unfortunately, been discovered in relatively few instances. To define the role of these gene products in the mechanism of cell division, it will be essential to combine the genetic approach with biochemical and morphological analysis. Yeasts have become favorite organisms for such studies because of ease of growth and manipulation, because of the sophisticated recombinant DNA and classic genetic techniques that have been developed (11,61), and because of the successful application of such techniques as electron microscopy and immunofluorescence (1,13,26,27,34,42).One of the proteins whose function in the cell division cycle is best understood is the a,,-tubulin heterodimer, which polymerizes to form the microtubules found in most eucaryotic cells (63). By electron and light microscopy, microtubules in yeast have been observed to be elements of structures involved in chromosome and nuclear movement (1,13,26,27,34,42

Perinuclear tethers license telomeric DSBs for a broad kinesin- and NPC-dependent DNA repair process

“…4a,g). We also assessed DSB repair in cells lacking the a-tubulin subunit Tub3 as a way to destabilize microtubules without inducing severe cellular defects linked to chemical-based microtubule perturbations 44 . Interestingly, tub3D cells displayed decreased DSB repair rates similar to those seen in cik1D cells (Fig.…”

Stu2, the Budding Yeast XMAP215/Dis1 Homolog, Promotes Assembly of Yeast Microtubules by Increasing Growth Rate and Decreasing Catastrophe Frequency

“…Although the ␣-and ␤-tubulins are highly evolutionarily conserved families of proteins, there are considerable differences between budding yeast and mammalian tubulins at both the gene and protein levels that might lead to this difference in Stu2 activity. Budding yeast has two ␣-tubulin genes and one ␤-tubulin gene (28,29), whereas vertebrates have six ␣-tubulin genes and seven ␤-tubulin genes (30). Within ␣-and ␤-tubulins, the sequence identity between yeast and mammalian proteins is only 70 -75%, with large differences at their C termini.…”

Role of the Cytoskeleton in Endocytosis of the Yeast Maltose Transporter

“…Yeast has a single gene, TUB2, that encodes -tubulin (Neff et al, 1983) and two genes, TUB1 and TUB3, that encode -tubulin (Schatz et al, 1986). These proteins are >70% identical to tubulins from animal cells, suggesting common biochemical properties.…”