Biomol Ther.  2021 Mar;29(2):234-247. 10.4062/biomolther.2020.166.

Systematic Target Screening Revealed That Tif302 Could Be an OffTarget of the Antifungal Terbinafine in Fission Yeast

Affiliations
  • 1Department of New Drug Development, Chungnam National University, Daejeon 34134, Republic of Korea
  • 2Department of Life Science, Dongguk University-Seoul, Goyang 10326, Republic of Korea
  • 3Personalized Genomic Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
  • 4Department of Biological Science, College of Bioscience & Biotechnology, Chungnam National University, Daejeon 34134, Republic of Korea
  • 5Korea United Pharm. Inc., Seoul 06116, Republic of Korea
  • 6Rare Disease Research Center, Korea Research Institute of Bioscience & Biotechnology (KRIBB), Daejeon 34141, Republic of Korea

Abstract

We used a heterozygous gene deletion library of fission yeasts comprising all essential and non-essential genes for a microarray screening of target genes of the antifungal terbinafine, which inhibits ergosterol synthesis via the erg1 enzyme. We identified 14 heterozygous strains corresponding to 10 non-essential [7 ribosomal-protein (RP) coding genes, spt7, spt20, and elp2] and 4 essential genes (tif302, rpl2501, rpl31, and erg1). Expectedly, their erg1 mRNA and protein levels had decreased compared to the control strain SP286. When we studied the action mechanism of the non-essential target genes using cognate haploid deletion strains, knockout of SAGA-subunit genes caused a down-regulation in erg1 transcription compared to the control strain ED668. However, knockout of RP genes conferred no susceptibility to ergosterol-targeting antifungals. Surprisingly, the RP genes participated in the erg1 transcription as components of repressor complexes as observed in a comparison analysis of the experimental ratio of erg1 mRNA. To understand the action mechanism of the interaction between the drug and the novel essential target genes, we performed isobologram assays with terbinafine and econazole (or cycloheximide). Terbinafine susceptibility of the tif302 heterozygous strain was attributed to both decreased erg1 mRNA levels and inhibition of translation. Moreover, Tif302 was required for efficacy of both terbinafine and cycloheximide. Based on a molecular modeling analysis, terbinafine could directly bind to Tif302 in yeasts, suggesting Tif302 as a potential off-target of terbinafine. In conclusion, this genome-wide screening system can be harnessed for the identification and characterization of target genes under any condition of interest.

Keyword

Antifungal; Terbinafine; Drug target; Ribosomal protein; Sterol; Translation
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