engleski

Illegitimate integration of single-stranded non-replicative plasmids in Saccharomyces cerevisiae chromosomes

Yeast transformation with non-replicative plasmids is considered to be mediated by recombination with homologous chromosomal sequences. However, we have found that the linearized single-stranded (ss) plasmids transform yeast cells mainly by illegitimate integration even in the presence of extended homology with the yeast genome. Integration of plasmid DNA occurs at different chromosomal loci and is very often associated with multiple and /or complex plasmid integrations. To further investigate the ability of ss plasmids to transform yeast cells via illegitimate integration, we developed an experimental system where transformation is performed in complete absence of homology between plasmid DNA and yeast genome. We used circular and linearized plasmids in either single- or double-stranded form. We found out that both linearized and circular ss plasmids transform yeast cells with approximately 100-fold higher efficiencies than their double-stranded counterparts. Possible role of single-stranded DNA in generation of genetic variability will be discussed.

yeast; illegitimate recombination; single-stranded DNA

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