Application of the comprehensive set of heterozygous yeast deletion mutants to elucidate the molecular basis of cellular chromium toxicity.

BACKGROUND: The serious biological consequences of metal toxicity are well documented, but the key modes of action of most metals are unknown. To help unravel molecular mechanisms underlying the action of chromium, a metal of major toxicological importance, we grew over 6,000 heterozygous yeast mutants in competition in the presence of chromium. Microarray-based screens of these heterozygotes are truly genome-wide as they include both essential and non-essential genes. RESULTS: The screening data indicated that proteasomal (protein degradation) activity is crucial for cellular chromium (Cr) resistance. Further investigations showed that Cr causes the accumulation of insoluble and toxic protein aggregates, which predominantly arise from proteins synthesised during Cr exposure. A protein-synthesis defect provoked by Cr was identified as mRNA mistranslation, which was oxygen-dependent. Moreover, Cr exhibited synergistic toxicity with a ribosome-targeting drug (paromomycin) that is known to act via mistranslation, while manipulation of translational accuracy modulated Cr toxicity. CONCLUSION: The datasets from the heterozygote screen represent an important public resource that may be exploited to discover the toxic mechanisms of chromium. That potential was validated here with the demonstration that mRNA mistranslation is a primary cause of cellular Cr toxicity.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Chromium causes aggregation predominantly of proteins synthesized during chromium exposure

<p><b>Copyright information:</b></p><p>Taken from "Application of the comprehensive set of heterozygous yeast deletion mutants to elucidate the molecular basis of cellular chromium toxicity"</p><p>http://genomebiology.com/2007/8/12/R268</p><p>Genome Biology 2007;8(12):R268-R268.</p><p>Published online 18 Dec 2007</p><p>PMCID:PMC2246270.</p><p></p> Cells were exposed to 0.1 mM CrOfor 60 minutes, either at the same time as or after labeling with [S]methionine for 60 minutes. The data show the relative enrichment of isotope in the aggregate fraction [cpm per μg aggregated protein, corrected for labeling efficiency (cpm per μg total protein)]. (b) Due to the natural turnover of labeled proteins during the post-labeling 60 minute incubation ± Cr, the data from this experiment were normalized with respect to the minus-Cr control from (a). Aggregated protein as a proportion of total protein was determined after incubation of cells for 1 h in the absence or presence of 0.4 mM CrOand 10 μg mlcycloheximide (CHX). All values are means ± standard error of the mean from three independent determinations