The overexpression of the efflux pump Tpo1 leads to the bleomycin resistance in Saccharomyces cerevisiae
Bleomycin is a cytotoxic antibiotic that, when used in combination with antineoplastic agents, has more genotoxic potential on testicular cancer than other types of cancer, which often develop resistance to the drugs. Our goal is to identify the resistance mechanism, using the organism Saccharomyces cerevisiae as a model. In our laboratory, we have demonstrated that deleted yeast strains on their transcriptional coactivator Imp2 have presented hypersensitivity to bleomycin due to the toxic accumulation inside the cell. This led us to believe that Imp2 might regulate the expression of one or more efflux pumps capable of expelling bleomycin outside the cell. To test our hypothesis, we sought multi-copy of suppressors capable of restoring bleomycin resistance in the mutant imp2. As a result we identified the transcriptional activator Yap1, which binds to a specific region within the promoter and activates the expression of subset of genes, encoding efflux pumps that are involved in drug resistance. Based on the literature, at least 27 efflux pumps have been identified in Saccharomyces cerevisiae. Some of these efflux pumps have binging sites for Yap1; such as Qdr3, Tpo2 and Tpo1. To determine whether or not one of these pumps expelled bleomycin, we proceded by single and double mutations in combination with IMP2. We also verified if these single and double mutants were sensitive to the drug, and then we have examined whether the overexpression of Yap1 could restore the wild phenotype in these mutants through the activation of efflux pumps.
Bleomycin testicular cancer Imp2 Yap1 Tpo1 Drug resistance