Abstract
We describe the results of a systematic search for a class of hitherto-overlooked chemical-genetic interactions in the Saccharomyces cerevisiae genome, which exists between a detrimental genetic mutation and a chemical/drug that can ameliorate, rather than exacerbate, that detriment. We refer to this type of interaction as “chemical suppression.” Our work was driven by the hypothesis that genome instability in a certain class of mutants could be alleviated by mild replication inhibition using chemicals/drugs. We queried a collection of conditionally lethal, i.e., temperature-sensitive, alleles representing 40% of the yeast essential genes for those mutants whose growth defect can be suppressed by hydroxyurea (HU), known as a potent DNA replication inhibitor, at the restrictive temperature. Unexpectedly, we identified a number of mutants defective in diverse cellular pathways other than DNA replication. Here we report that HU suppresses selected mutants defective in the kinetochore-microtubule attachment pathway during mitotic chromosome segregation. HU also suppresses an ero1-1 mutant defective for a thiol oxidase of the endoplasmic reticulum by providing oxidation equivalents. Finally, we report that HU suppresses an erg26-1 mutant defective for a C-3 sterol dehydrogenase through regulating iron homeostasis and in turn impacting ergosterol biosynthesis. We further demonstrate that cells carrying the erg26-1 mutation show an increased rate of mitochondrial DNA loss and delayed G1 to S phase transition. We conclude that systematic gathering of a compendium of “chemical suppression” of yeast mutants by genotoxic drugs will not only enable the identification of novel functions of both chemicals and genes, but also have profound implications in cautionary measures of anticancer intervention in humans.
Highlights
We describe the results of a systematic search for a class of hitherto-overlooked chemicalgenetic interactions in the Saccharomyces cerevisiae genome, which exists between a detrimental genetic mutation and a chemical/drug that can ameliorate, rather than exacerbate, that detriment
Our work was inspired by the observation that the DNA replication inhibitor hydroxyurea (HU) can rescue a mutant carrying a temperaturesensitive allele of the Aurora B kinase, whose inactivation leads to defective chromosome segregation and genome instability (Figure 2) (Lampson and Cheeseman 2011)
We have described a novel chemical-genetic screen to identify mutations whose defects can be suppressed by a DNA replication inhibitor, HU
Summary
We describe the results of a systematic search for a class of hitherto-overlooked chemicalgenetic interactions in the Saccharomyces cerevisiae genome, which exists between a detrimental genetic mutation and a chemical/drug that can ameliorate, rather than exacerbate, that detriment. Our work was inspired by the observation that the DNA replication inhibitor hydroxyurea (HU) can rescue a mutant carrying a temperaturesensitive allele (ipl1-321) of the Aurora B kinase, whose inactivation leads to defective chromosome segregation and genome instability (Figure 2) (Lampson and Cheeseman 2011). We referred to this type of interaction as “chemical suppression” and reasoned that there should be other mutants whose phenotypes are alleviated by HU, either through its replication inhibitory function and/or other unknown functions. In all these studies the screen was based on the concept of “many molecules vs. single phenotype.” To the best of our knowledge, a screen based on the “single molecule and many phenotypes” concept and to catalog “suppression” events has not yet been conducted
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