[Saccharomyces cerevisiae mutants with increased mitotic stability of plasmids isolated during long-term culturing of transformants under selective conditions].

Analysis of the plasmid containing clones of transformants of Saccharomyces cerevisiae in the population cultivated under the nonselective conditions has shown their vast heterogeneity in the mitotic stability of the plasmids Yep13 and Yep91. For instance, the clones were obtained with the different types of the hereditary plasmid stabilization: integration with the chromosome and genotype or plasmid mutations increasing the vector copy number. The increased expression level was registered in the mutants for the heterologous genes AmpR of Escherichia coli and HBsAg of hepatitis B. The clones were found with the considerably varying mitotic stability of the plasmids of the modification type variability, the latter expressing the fluctuations of plasmid copy number at the change of cultivation conditions.