Simultaneous expression of both MAT loci in haploid cells suppresses mutations in yeast microtubule motor genes

Abstract.

The kinesin-related Cin8p and cytoplasmic dynein are microtubule-associated motor proteins required for anaphase spindle elongation in the yeast Saccharomyces cerevisiae. Cells deleted for DYN1 (the gene encoding the dynein heavy chain) and carrying the temperature-sensitive allele cin8-3 cannot grow at temperatures above 35°C. Here, we report that the temperature sensitivity of haploid cin8-3 dyn1Δ cells is suppressed by the simultaneous presence of the loci MATa and MATα, which contain the regulatory genes that determine mating-type and ploidy-dependent phenotypes. The presence of the two MAT loci also rendered haploid cells more resistant to the anti-microtubule drug benomyl. Our results suggest that, in preparation for handling double the amount of DNA in mitosis, properties of microtubules in diploid cells are modified in a pathway controlled by the mating-type regulatory genes.