Chemogenomic profiling of nitrosamines in yeast

We used the yeast chemogenomic assay to screen N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine and N-methyl-N-aminobutyric acid), their metabolic intermediates (methylamine, ethylamine, formamide and formaldehyde) and related compounds (N,N-dimethylformamide, ammonium sulfate and 4-Nitroquinoline-1-oxide). This work was inspired by the global recalls of sartan class of medications after N-nitrosamine contaminants were detected. In our experiment, a pool containing equal amounts of each of 4,800 homozygous yeast deletion strains were challenged with each compound at 10-20% inhibitory dose and grown competitively for five generations. We used barcode next generation sequencing to quantitatively determine relative strain abundance, and thus estimated the sensitivity or resistance of each strain against the compounds. We found several genes and pathways are required for nitrosamines toxicity, including the arginine biosynthetic pathway. To confirm the involvement of arginine biosynthesis in nitrosamine toxicity, we selected nineteen deletion strains that are of arginine and ammonium metabolism and tested them against these compounds. The attached files contain the count matrices from the barcode sequencing data, as well as the optical density versus time readings during the confirmation screens.