Mapping Synthetic Dosage Lethal Genetic Interactions in Saccharomyces cerevisiae

Synthetic dosage lethality (SDL) is a type of genetic interaction that occurs when increasing the expression of a gene causes a fitness defect, such as lethality, in a specific mutant background but has little effect on fitness in a wild-type background. SDL genetic interactions discovered in model organisms such as the budding yeast, Saccharomyces cerevisiae , represent candidate genetic interactions that may be conserved in human cells. In some cases, SDL genetic interactions can be applied to study the biological implications of genes overexpressed in cancer and to discover potential anticancer therapeutic drug targets. Here, we provide a protocol for screening a query overexpression gene against ordered arrays of yeast mutant strains to identify mutations that sensitize yeast to increased dosage of a specific gene product. We outline applications and procedures for screening with an inducibly overexpressed wild-type gene, a common feature of cancer cells, or with an inducibly overexpressed gene carrying a dominant-negative missense mutation as a model of protein-inhibitor interactions. This high-throughput screening platform is adapted from synthetic genetic array (SGA) technology and enables the generation of large-scale SDL genetic interaction networks that can be applied to study gene/pathway function and to identify cross-species cancer-relevant processes.