Abstract
Cells have developed a variety of mechanisms to respond to heavy metal exposure. Here, we show that the yeast ubiquitin ligase SCF(Met30) plays a central role in the response to two of the most toxic environmental heavy metal contaminants, namely, cadmium and arsenic. SCF(Met30) inactivates the transcription factor Met4 by proteolysis-independent polyubiquitination. Exposure of yeast cells to heavy metals led to activation of Met4 as indicated by a complete loss of ubiquitinated Met4 species. The association of Met30 with Skp1 but not with its substrate Met4 was inhibited in cells treated with cadmium. Cadmium-activated Met4 induced glutathione biosynthesis as well as genes involved in sulfuramino acid synthesis. Met4 activation was important for the cellular response to cadmium because mutations in various components of the Met4-transcription complex were hypersensitive to cadmium. In addition, cell cycle analyses revealed that cadmium induced a delay in the transition from G(1) to S phase of the cell cycle and slow progression through S phase. Both cadmium and arsenic induced phosphorylation of the cell cycle checkpoint protein Rad53. Genetic analyses demonstrated a complex effect of cadmium on cell cycle regulation that might be important to safeguard cellular and genetic integrity when cells are exposed to heavy metals.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing
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Anaphase-Promoting Complex-Cyclosome
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Autophagy-Related Proteins
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Cadmium / pharmacology*
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Carrier Proteins / metabolism
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Cell Cycle / drug effects
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Cell Cycle Proteins / metabolism
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Checkpoint Kinase 2
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F-Box Proteins / metabolism
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Hydrogen Peroxide / pharmacology
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Methionine / genetics
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Methionine / metabolism
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Phosphorylation / drug effects
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Protein Binding / drug effects
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Protein Serine-Threonine Kinases / metabolism
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Repressor Proteins / genetics
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Repressor Proteins / metabolism*
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SKP Cullin F-Box Protein Ligases / metabolism
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Saccharomyces cerevisiae / drug effects*
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Saccharomyces cerevisiae / enzymology*
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Ubiquitin-Protein Ligase Complexes / genetics
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Ubiquitin-Protein Ligase Complexes / metabolism*
Substances
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Adaptor Proteins, Signal Transducing
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Autophagy-Related Proteins
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Carrier Proteins
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Cell Cycle Proteins
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F-Box Proteins
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MET30 protein, S cerevisiae
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Repressor Proteins
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Saccharomyces cerevisiae Proteins
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UBQLN1 protein, human
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Cadmium
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Methionine
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Hydrogen Peroxide
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Ubiquitin-Protein Ligase Complexes
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Anaphase-Promoting Complex-Cyclosome
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SKP Cullin F-Box Protein Ligases
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SKP1 protein, S cerevisiae
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Checkpoint Kinase 2
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Protein Serine-Threonine Kinases
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RAD53 protein, S cerevisiae