Functional profiling of formaldehyde in yeast

Formaldehyde (FA) is a commercially important chemical with numerous and diverse uses. In this study, a functional toxicogenomics approach was utilized in the model eukaryotic yeast Saccharomyces cerevisiae to identify genes and cellular processes modulating the cellular toxicity of FA. Our results demonstrate mutant strains deficient in multiple DNA repair pathways were sensitive to FA. The SKI complex and its associated factors, which regulate mRNA degradation by the exosome, were also required for FA tolerance.. Pools of homozygous diploid deletion mutants (n = 4,607 strains) were grown in formaldehyde at 3 concentrations for 5 and 15 generations (5g, 15g). Each strain has a deletion in a different gene. In each strain, the gene was replaced by a deletion cassette containing a antibiotic resistance gene and two BARCODES, up and down tags (Please see Giaever et al, 2002, Nature). These tags in the DNA are specific to each strain. We pool all deletion strains and grow them under a selective condition; extract DNA; amplify barcodes using universal primers and hybridize to arrays containing complementary sequences to the up and down tags. In this way, we can look at growth of each of the strains. Our strategy is to analyze separately the up and down tags. Therefore, for each array (CEL file), we generate two data files, one for all ups and another one for all downs. In these files, the list of genes are the same but the data come from different set of probes, up or down. The values are log2 averages of replicate probes for the same tag. These pre processed files were used to identify strains with differential growth in formaldehyde by comparing to control arrays.