Overexpression of the ubiquitin-conjugating enzyme Cdc34 confers resistance to methylmercury in Saccharomyces cerevisiae.
A search was made for genes that confer resistance to methylmercury in yeast using a genomic DNA library derived from Saccharomyces cerevisiae. The genomic library was introduced into yeast and transformants that grew in the presence of a normally toxic concentration of methylmercury were selected. We sequenced the genomic DNA fragment in the plasmid from the clone with the highest resistance to methylmercury and analyzed the sequence for presence of an open reading frame that might confer resistance to methylmercury. We identified a gene, CDC34 (also known as UBC3), that increased resistance to methylmercury when overexpressed in yeast. CDC34 encodes a ubiquitin-conjugating enzyme; such proteins play important roles in the selective targeting of proteins for degradation. Overexpression of UBC4 and of UBC7, two other genes for ubiquitin-conjugating enzymes, also conferred resistance to methylmercury. Yeast strains transformed with the CDC34 gene were resistant not only to methylmercury but also to mercuric chloride and p-chloromercuribenzoate. To our knowledge, this is the first demonstration that overexpression of genes for ubiquitin-conjugating enzymes confers resistance to xenobiotics. Our results suggest that ubiquitination system might be involved in protection against the toxicity of mercury compounds, such as methylmercury, in eukaryotic cells.
Furuchi
Takemitsu
T
Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Hwang
Gi-Wook
GW
Naganuma
Akira
A
D064173:Anaphase-Promoting Complex-Cyclosome; D004352:Drug Resistance, Microbial / Q000235:genetics* / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression; D008025:Ligases / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D008767:Methylmercury Compounds / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes
D005656:Fungal Proteins; D008767:Methylmercury Compounds; D029701:Saccharomyces cerevisiae Proteins; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D008025:Ligases; C004925:methylmercuric chloride