We study the molecular mechanisms by which extrachromosomal
DNA elements maintain themselves stably and at relatively high copy numbers without endangering their host organisms. The model system we employ is the 2 micron plasmid of Saccharomyces cerevisiae. The plasmid has a copy number of approximately 60 per cell, and is rarely lost during cell division. The high plasmid stability is ensured by a partitioning system that includes two plasmid
proteins and a cis-acting DNA locus. The plasmid also utilizes an amplification mechanism to compensate for rare stochastic downward fluctuations
in copy number. A site-specific DNA recombination
system encoded by the plasmid is responsible for this copy number control.
The research projects in the laboratory explore recombination
mechanisms, test models for recombination mediated DNA amplification
and examine plasmid segregation using tools of molecular genetics and cell biology.