Undimerized beta-tubulin is toxic in the yeast S. cerevisiae. It can arise if levels of beta-tubulin and alpha-tubulin are unbalanced or if the tubulin heterodimer dissociates. We are using the toxicity of beta-tubulin to understand early steps in microtubule morphogenesis. We find that deletion of PLP1 suppresses toxic beta-tubulin formed by disparate levels of alpha- and beta-tubulin. That suppression occurs either when alpha-tubulin is modestly underexpressed relative to beta-tubulin or when beta-tubulin is inducibly and strongly overexpressed. Plp1p does not affect tubulin expression. Instead, a significant proportion of the undimerized beta-tubulin in plp1Delta cells is less toxic than that in wild-type cells. It is also less able to combine with alpha-tubulin to form a heterodimer. As a result, plp1Delta cells have lower levels of heterodimer. Importantly, plp1Delta cells that also lack Pac10, a component of the GimC/PFD complex, are even less affected by free beta-tubulin. Our results suggest that Plp1p defines a novel early step in beta-tubulin folding.

• PMID: 14573467
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, P.H.S.

Authors

Lacefield S, Solomon F

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