Isolation of overexpressed yeast genes which prevent aminoglycoside toxicity.

Aminoglycoside antibiotics at non-toxic levels can cause sensorineural hearing loss in genetically predisposed individuals. The major aminoglycoside hypersensitivity mutation that has been described in humans is at position 1555 in the mitochondrial 12S ribosomal RNA gene. In order to identify additional candidate genes for genetic susceptibility mutations in humans and possibly develop therapeutic interventions, we are using yeast as a model organism to identify genes whose products interact with aminoglycosides or bypass the effects of aminoglycoside poisoning. We have selected yeast genomic DNAs that, when cloned into a high copy number plasmid, confer neomycin resistance. We have previously described the first gene identified through this approach [Prezant, Chaltraw and Fischel-Ghodsian, Microbiology 142 (1996) 3407 3414] and have now completed this search by the exhaustive screening of 35 yeast genome equivalents. This has resulted in the identification of seven additional chromosomal regions. All seven chromosomal regions have been characterized and the most likely gene responsible for aminoglycoside resistance has been identified for each of them. While the mechanism of aminoglycoside resistance can be inferred for some of the gene products, it remains to be determined for others.