Flowchart describing the yeast genetic interaction screen. (A) The 20 toxic OMIM genes were transformed individually into a pool of 4653 yeast homozygous deletion strains containing a 20-bp DNA barcode sequence. Transformants were selected in SD-Leu medium for 16 h and then washed twice with PBS. The cells were resuspended in SGal-Leu medium and incubated for 2 d to induce the expression of OMIM genes under the control of the GAL1 promoter. Genomic DNA was separately isolated from cells harvested at the end of pooled culture in the presence of GLU or GAL. (B) Barcodes were amplified from genomic DNA with multiplexed primers containing distinct combinations of two different tags for each OMIM gene. Equal amounts of DNA amplified for each OMIM gene were pooled and subjected to multiplex barcode sequencing using an Illumina Genome Analyzer. Next-generation sequencing data were then analyzed for barcode counting.
