A region in the yeast genome which favours multiple integration of DNA via homologous recombination.

Integrative transformation of yeast with gapped DNA fragments results in single or multiple integration into the yeast genome via homologous recombination. A sequence of yeast DNA was found which favours multiple integration even when the strategy of gene replacement is used. This strategy by which the transformed DNA fragment replaces its chromosomal homologue rather than simply integrating into the genome usually occurs as a single exchange event. The described region is unique and lies near a telomere about 5 kb proximal to the SUC4 locus on chromosome XIII. DNA from this region was used as a vehicle for the integration of different SUC genes coding for invertase. Most of the sucrose fermenting transformants isolated carried between two and seven copies of the SUC genes. These transformants overproduced invertase even though there was no selective pressure for high invertase activity in these experiments. I conclude that this region is highly recombinogenic and favours multiple integration of DNA fragments. This region could be used for stable multiple integration of heterologous genes into the yeast genome for over-production of the respective gene product.