Identification of the pleiotropic cell division cycle gene NDA2 as one of two different alpha-tubulin genes in Schizosaccharomyces pombe.

Mutations in a cell-cycle gene NDA2 of Schizosaccharomyces pombe have pleiotropic effects on nuclear division, nuclear location, and thiabendazole sensitivity ( Toda et al., 1983). By transformation and nucleotide sequence determination, we identified NDA2 as one of two alpha-tubulin genes present in the genome of S. pombe. Two cloned sequences complemented cold-sensitive and thiabendazole-supersensitive nda2 mutations; one was derived from NDA2 that encodes alpha 1-tubulin, the other from an unidentified locus encoding alpha 2-tubulin. The predicted amino acid sequences showed that the alpha 1- and alpha 2-tubulins had respective residues of 455 and 449 (molecular weights 51,200 and 50,600). The homology to porcine alpha-tubulin was 76% in both cases. Frequent alterations took place in the two restricted regions. The alpha 1-tubulin (NDA2) clone had a 90 bp intervening sequence, the alpha 2-tubulin clone did not. RNA blot hybridization experiments indicated that both genes are transcribed. S. pombe tubulin was isolated by cycles of assembly and disassembly. Presumed alpha- and beta-tubulin polypeptide bands reacted with monoclonal antibodies specific for chicken alpha- and beta-tubulins.