Molecular and General Genetics MGG

, Volume 146, Issue 3, pp 253–259

The molecular events involved in the induction of petite yeast mutants by fluorinated pyrimidines

  • Stephen G. Oliver
  • Donald H. Williamson

DOI: 10.1007/BF00701248

Cite this article as:
Oliver, S.G. & Williamson, D.H. Molec. Gen. Genet. (1976) 146: 253. doi:10.1007/BF00701248


The fluorinated pyrimidines 5-fluorouracil (5FU) and 5-fluorocytosine (5FC) induce the cytoplasmic petite mutation in the yeastSaccharomyces cerevisiae with high efficiency. It was found that in order to induce the mutation, 5FC must first be deaminated to 5FU. However, mutagenesis does not depend on the further conversion of 5FU to its deoxyriboside (5FUDR) and subsequent blockade of intracellular thymidine synthesis, since 5FUDR itself was found not to be mutagenic, and 5FU-induced mutagenesis was not antagonised by supplying thymidine monophosphate (dTMP) to a dTMP permeable strain. In any case, observations of the molecular changes accompanying petite induction in log phase cells ruled out the possibility that mutagenesis resulted simply from the dilution out of replication-blocked mitDNA molecules, since the appearance of mutants coincided with the synthesis of altered mitDNA molecules. In different strains, the resulting defective molecules were either maintained, giving rise to suppressiveρ petites, or completely degraded, to give pure clones of neutralρ0 mutants. It is suggested that this degradative process was a consequence of the incorporation of 5FU into RNA.

Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • Stephen G. Oliver
    • 1
  • Donald H. Williamson
    • 1
  1. 1.National Institute for Medical ResearchLondonEngland
  2. 2.Department of Molecular Biology and BiochemistryUniversity of CaliforniaIrvineUSA

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