Isolation of a taxol-resistant Chinese hamster ovary cell mutant that has an alteration in alpha-tubulin.

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Abstract
Taxol is a plant alkaloid that has antimitotic activity and appears to stabilize microtubules. Taxol-resistant cells were selected from a population of UV-mutagen-treated Chinese hamster ovary cells by a single-step procedure. These mutants have normal morphologies and growth rates but are 2- to 3-fold more resistant to the toxic effects of the drug than the wild-type parent. One of 20 mutants screened by 2-dimensional electrophoresis for chemical alterations in tubulin had an extra spot with a more acidic isoelectric point than .alpha.-tubulin. This extra spot was an electrophoretic variant .alpha.-tubulin by its copurification with tubulin in crude microtubule- containing preparations and by 1-dimensional peptide mapping. The .alpha.-tubulin mutant was temperature sensitive for growth, and this property was used as the basis for the selection of revertants. Seventeen temperature-resistant revertants of the .alpha.-tubulin mutant were selected for their ability to grow at 40.degree. C and 3 of these revertants had simultaneously lost their taxol resistance and the electrophoretic variant .alpha.-tubulin. An alteration in .alpha.-tubulin evidently can confer taxol resistance on a mammalian cell line and suggest that .alpha.-tubulin is essential for cell viability.