A genome-wide screening of target genes against silver nanoparticles in fission yeast

To identify target genes against silver nanoparticles (AgNPs), we screened a genome-wide gene deletion library of 4843 fission yeast heterozygousmutants covering 96% of all protein encoding genes. A total of 33 targets were identified by amicroarray and subsequent individual confirmation. The target pattern of AgNPs wasmore similar to those of AgNO₃ and H₂O₂, followed by Cd and As. The toxic effect of AgNPs on fission yeast was attributed to the intracellular uptake of AgNPs, followed by the subsequent release of Ag⁺, leading to the generation of reactive oxygen species (ROS). Next, we focused on the top 10 sensitive targets for further studies. As described previously, 7 nonessential targets were associated with detoxification of ROS, because their heterozygousmutants showed elevated ROS levels. Three novel essential targets were related to folate metabolismor cellular component organization, resulting in cell cycle arrest and no induction in the transcriptional level of antioxidant enzymes such as Sod1 and Gpx1 when 1 of the 2 copies was deleted. Intriguingly, met9 played a key role in combating AgNP-induced ROS generation via NADPH production and was also conserved in a human cell line.