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

Abstract

Chromium toxicity <p>Competitive growth between over 6,000 heterozygous yeast mutants in the presence of chromium together with microarray-based screens showed that proteasomal activity is crucial for cellular chromium resistance.</p> Abstract 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 nonessential genes.

Arsenite interferes with protein folding and triggers formation of protein aggregates in yeast

“…In contrast to As(III), Cr suppressed red pigmentation of the ade1-14 strain (Holland et al, 2007) and caused a strong synergistic toxicity with paromomycin ( Fig. 3C), consistent with the notion that Cr induces mistranslation (Holland et al, 2007). We conclude that As(III) is not an efficient inducer of protein mistranslation.…”

“…Sodium arsenite (NaAsO 2 ), chromium trioxide (CrO 3 ), cadmium chloride (CdCl 2 ), paromomycin sulfate, and cycloheximide (CHX) (all from Sigma-Aldrich) were added to the cultures at the indicated concentrations. Mistranslation was scored using a qualitative plate assay as previously described (Holland et al, 2007).…”

“…It is possible that Cd and Cr do not enter cells as efficiently as As(III). Alternatively, the observed difference in potency could be a consequence of distinct modes of biological action; for example, Cr causes protein mistranslation (Holland et al, 2007) whilst As(III) does not (Fig. 3); As(III) interferes with CCT activity in vitro whilst Cd does not (Pan et al, 2010).…”

“…S. cerevisiae responds to As(III) exposure by strongly enhancing expression of chaperoneand proteasome-encoding genes; upregulation of proteasomal components is mediated by the transcription factor Rpn4p and cells lacking this factor are As(III) sensitive (Haugen et al, 2004;Thorsen et al, 2007;Thorsen et al, 2009). Rpn4p is also required for Cd (Thorsen et al, 2009) and Cr tolerance (Holland et al, 2007). Together, these observations suggest that metal-treated cells may accumulate damaged proteins that need to be eliminated for optimal tolerance.…”

A genome-wide screen identifies yeast genes required for protection against or enhanced cytotoxicity of the antimalarial drug quinine

“…The high degree of conservation between the basic cellular processes of yeast and higher eukaryotes, together with the plethora of postgenomic tools available, make this model organism a robust and inexpensive platform to study the effects and targets of drugs as well as drug resistance mechanisms on more complex and less accessible organisms (Parsons et al 2003;Mager and Winderickx 2005;Foury 1997). The use of yeast deletion mutant collections has been in particular evidence in recent years, having been used in several genome-wide studies to identify new genes/pathways important for survival to various cellular insults, namely anti-cancer drugs (Aouida et al 2004;Hellauer et al 2005;Huang et al 2005), heavy metals (Holland et al 2007;Ruotolo et al 2008), antimicrobials (Blackburn and Avery 2003;Morton et al 2007) and anti-malarial drugs (Khozoie et al 2009;Li et al 2005), including quinine. Our group has recently profiled the yeast transcriptomic response to quinine (dos Santos et al 2009).…”