MCHM Acts as a Hydrotrope, Altering the Balance of Metals in Yeast

Pupo, Amaury; Ayers, Michael C.; Sherman, Zachary; Vance, Rachel J.; Cumming, Jonathan R.; Gallagher, Jennifer E. G.

doi:10.1007/s12011-019-01850-z

Cited by 9 publications

(35 citation statements)

References 51 publications

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“…We used a data set generated previously by our laboratory and available from https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE108873 [43]. For this analysis, we kept only the data regarding wild type S288c strain in YPD, treated or not with MCHM by 90 minutes.…”

Section: Resultsmentioning

confidence: 99%

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Effects of MCHM on yeast metabolism

Pupo

Gallagher

2019

PLoS ONE

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On January 2014 approximately 10,000 gallons of crude 4-Methylcyclohexanemethanol (MCHM) and propylene glycol phenol ether (PPH) were accidentally released into the Elk River, West Virginia, contaminating the tap water of around 300,000 residents. Crude MCHM is an industrial chemical used as flotation reagent to clean coal. At the time of the spill, MCHM's toxicological data were limited, an issue that has been addressed by different studies focused on understanding the immediate and long-term effects of MCHM on human health and the environment. Using S. cerevisiae as a model organism we study the effect of acute exposure to crude MCHM on metabolism. Yeasts were treated with MCHM 550 ppm in YPD for 30 minutes. Polar and lipid metabolites were extracted from cells by a chloroform-methanol-water mixture. The extracts were then analyzed by direct injection ESI-MS and by GC-MS. The metabolomics analysis was complemented with flux balance analysis simulations done with genome-scale metabolic network models (GSMNM) of MCHM treated vs non-treated control. We integrated the effect of MCHM on yeast gene expression from RNA-Seq data within these GSMNM. A total of 215 and 73 metabolites were identified by the ESI-MS and GC-MS procedures, respectively. From these 26 and 23 relevant metabolites were selected from ESI-MS and GC-MS respectively, for 49 unique compounds. MCHM induced amino acid accumulation, via its effects on amino acid metabolism, as well as a potential impairment of ribosome biogenesis. MCHM affects phospholipid biosynthesis, with a potential impact on the biophysical properties of yeast cellular membranes. The FBA simulations were able to reproduce the deleterious effect of MCHM on cellular growth and suggest that the effect of MCHM on ubiquinol:ferricytochrome c reductase reaction, caused by the under-expression of CYT1 gene, could be the driven force behind the observed effect on yeast metabolism and growth.

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Section: Resultsmentioning

confidence: 99%

“…A fraction of previously reported data was used, including only the samples with wildtype S288c (S96 lys5) cells in YPD treated or not with MCHM [43]. The RNA-seq of S96 was carried out on hot acid phenol extracted RNA [44].…”

Section: Methodsmentioning

confidence: 99%

Effects of MCHM on yeast metabolism

Pupo

Gallagher

2019

PLoS ONE

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“…MCHM is a coal-cleaning chemical that acts as a hydrotrope in vitro (22). Hydrotropes increase the solubility of organic compounds by inducing liquid phase condensates.…”

Section: Introductionmentioning

confidence: 99%

“…These types of hydrotropes act to concentrate compounds. Exposure to MCHM induced growth arrest in yeast by changing a wide range of biochemical pathways including ionome (22) and amino acids (27). The Mediator binds upstream of many genes across pathways, including stress responsive genes.…”

Section: Introductionmentioning

confidence: 99%

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The polymorphic PolyQ tail protein of the Mediator Complex, Med15, regulates variable response to stress

Gallagher

Nassif

Pupo

2019

Preprint

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The Mediator is a multi-protein complex composed of subunits called head, body, tail, and CDK that is conserved from yeast to humans and plays a central role in transcription. However, not all the components are required for basal transcription. Components of the tail are not essential but to varying degrees are required for growth in different stresses. While some stresses are familiar such as heat, desiccation, and starvation, others are exotic, yet yeast can elicit a successful stress response. MCHM is a hydrotrope that induces growth arrest in yeast. By exploiting genetic variation, specifically in Med15, between yeast strains, we found that a naturally occurring Med15 allele with polyQ (polyglutamine) expansion conferred MCHM sensitivity. Expansion in polyQ repeat can induce protein aggregation and in humans can cause neurodegenerative diseases. In yeast, the MCHM sensitivity was not from a loss of function as the reciprocal hemizygous hybrids were all sensitive and the homozygous null mutant was less sensitive than the hemizygous hybrids. This suggests that there is an incompatibility between Mediator components from genetic divergent yeast strains. Transcriptomics from yeast expressing the incompatible Med15 (longer polyQ repeats in the strain with fewer repeats) changed gene expression in diverse pathways. Med15 protein existed in multiple isoforms, mostly from likely post-translational modifications and different alleles have different patterns of isoforms. Stability of both alleles of Med15 was dependent on Ydj1, a J-type chaperone. The protein level of the incompatible Med15 allele was lower than the compatible allele and was turned over faster. Med15 is tethered to the rest of the Mediator complex via Med2 and 3. Deletion of either Med2 or Med3 changed the Med15 isoform patterns in a similar manner. Whereas deletion of Med5, a distal component of the Mediator tail, did not change the pattern. The med2 and med3 mutants were similarly sensitive to MCHM while med5 mutants were not. Differences in the phenotype of yeast carrying different Med15 alleles extend to other stresses. The incompatible allele of Med15 improved growth of yeast to chemicals that produce free radicals and the compatible allele of Med15 improved growth to reducing agents, caffeine, and hydroxyurea. Med15 directly interacts with Gcn4 and other TFs and in vitro form phaseseparated droplets. This variation may reflect the positive and negative role that Med15 has in transcription. Genetic variation in transcriptional regulators can magnify differences in response to environmental changes, in contrast, genetic variation in a metabolic enzyme. These polymorphic control genes are master variators.

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