biostudies-literatureWethekam LCNational Institutes of HealthUniversity of Colorado Molecular Biology Training ProgramNIH HHSNIGMS NIH HHSe202202102https://www.ebi.ac.uk/biostudies/studies/S-EPMC9930134biostudies-literatureUnknown222(3)How cells regulate α- and β-tubulin to meet the demand for αβ-heterodimers and avoid consequences of monomer imbalance is not understood. We investigate the role of gene copy number and how shifting expression of α- or β-tubulin genes impacts tubulin proteostasis and microtubule function in Saccharomyces cerevisiae. We find that α-tubulin gene copy number is important for maintaining excess α-tubulin protein compared to β-tubulin protein. Excess α-tubulin prevents accumulation of super-stoichiometric β-tubulin, which leads to loss of microtubules, formation of non-microtubule assemblies of tubulin, and disrupts cell proliferation. In contrast, sub-stoichiometric β-tubulin or overexpression of α-tubulin has minor effects. We provide evidence that yeast cells equilibrate α-tubulin protein concentration when α-tubulin isotype expression is increased. We propose an asymmetric relationship between α- and β-tubulins, in which α-tubulins are maintained in excess to supply αβ-heterodimers and limit the accumulation of β-tubulin monomers.The Journal of cell biologyTubulin isotype regulation maintains asymmetric requirement for α-tubulin over β-tubulin.PMC9930134T32 GM136444R01 GM112893Bolie Scholar AwardR35 GM 136253R35 GM136253Wethekam LCMoore JKfalseTubulin isotype regulation maintains asymmetric requirement for α-tubulin over β-tubulin.How cells regulate α- and β-tubulin to meet the demand for αβ-heterodimers and avoid consequences of monomer imbalance is not understood. We investigate the role of gene copy number and how shifting expression of α- or β-tubulin genes impacts tubulin proteostasis and microtubule function in Saccharomyces cerevisiae. We find that α-tubulin gene copy number is important for maintaining excess α-tubulin protein compared to β-tubulin protein. Excess α-tubulin prevents accumulation of super-stoichiometric β-tubulin, which leads to loss of microtubules, formation of non-microtubule assemblies of tubulin, and disrupts cell proliferation. In contrast, sub-stoichiometric β-tubulin or overexpression of α-tubulin has minor effects. We provide evidence that yeast cells equilibrate α-tubulin protein concentration when α-tubulin isotype expression is increased. We propose an asymmetric relationship between α- and β-tubulins, in which α-tubulins are maintained in excess to supply αβ-heterodimers and limit the accumulation of β-tubulin monomers.2023-01-01T00:00:00Z2023 Mar2026-03-18T14:09:32.19Z2025-04-04T22:55:17.112ZS-EPMC99301343671940010.1083/jcb.202202102