Effects of MCHM on yeast metabolism

Metabolomic approach for phytochemical assessment of Murraya koenigii fruits during different maturity stages

A detailed metabolomic study was performed on various maturation stages of Murraya koenigii fruit pulps, seed, and leaf. Among the fruit pulps, stage 6 had the highest TPC (13.27 mg/g of GAE) and TFC content (6.16 mg/g RE). The extracts also showed promising free radical scavenging activity, especially in the seed (IC50DPPH 427 μg/mL). Metabolomics study revealed the identification of 133 metabolites in fruit pulps, seeds and leaves using the METLIN database. In silico PASS software analysis predicted the antimutagenic property of myricetin and bismurrayaquinone A. Pathway analysis revealed the phenylpropanoid biosynthesis pathway as one of the major pathways present in the fruit pulps. This detailed metabolic report of M. koenigii fruit maturation report brings a new insight into phytochemicals and their distribution in seed, pulps and leaves along with nutritive values and can be considered for nutritive and therapeutic purposes.

4-Methylcyclohexane methanol (MCHM) affects viability, development, and movement of Xenopus embryos

Following chemical spill disasters, it is important to estimate the effects of spilled chemicals on humans and the environment. Here we analyzed the toxicological effects of the coal cleaning chemical, 4-methylcyclohexane methanol (MCHM), which was spilled into the Elk River water supply in 2014. The viability of HEK293 T human cell line cultures and Xenopus tropicalis embryos was negatively affected, and the addition of the antioxidants alleviated toxicity with MCHM exposure. Additionally, X. tropicalis embryos suffered developmental defects as well as reversible non-responsiveness and melanization defects. The impact MCHM has on HEK293 T cells and X. tropicalis points to the importance of continued follow-up studies of this chemical.

Oxidative Stress Responses and Nutrient Starvation in MCHM Treated Saccharomyces cerevisiae

In 2014, the coal cleaning chemical 4-methylcyclohexane methanol (MCHM) spilled into the water supply for 300,000 West Virginians. Initial toxicology tests showed relatively mild results, but the underlying effects on cellular biology were underexplored. Treated wildtype yeast cells grew poorly, but there was only a small decrease in cell viability. Cell cycle analysis revealed an absence of cells in S phase within thirty minutes of treatment. Cells accumulated in G1 over a six-hour time course, indicating arrest instead of death. A genetic screen of the haploid knockout collection revealed 329 high confidence genes required for optimal growth in MCHM. These genes encode three major cell processes: mitochondrial gene expression/translation, the vacuolar ATPase, and aromatic amino acid biosynthesis. The transcriptome showed an upregulation of pleiotropic drug response genes and amino acid biosynthetic genes and downregulation in ribosome biosynthesis. Analysis of these datasets pointed to environmental stress response activation upon treatment. Overlap in datasets included the aromatic amino acid genes ARO1, ARO3, and four of the five TRP genes. This implicated nutrient deprivation as the signal for stress response. Excess supplementation of nutrients and amino acids did not improve growth on MCHM, so the source of nutrient deprivation signal is still unclear. Reactive oxygen species and DNA damage were directly detected with MCHM treatment, but timepoints showed these accumulated slower than cells arrested. We propose that wildtype cells arrest from nutrient deprivation and survive, accumulating oxidative damage through the implementation of robust environmental stress responses.

Metallomic and lipidomic analysis of S. cerevisiae response to cellulosic copper nanoparticles uncovers drivers of toxicity

Nanotechnology is a promising new technology, of which antimicrobial metal nanocomposites are predicted to become valuable in medical and food packaging applications. Copper is a redox-active antimicrobial metal that can become increasingly toxic depending on the target biomolecule's donor atom selectivity and the chemical species of copper present. Mass is the traditional measurement of the intrinsic elemental chemistry, but this practice fails to reflect the morphology and surface area reactivity of nanotechnology. The carboxymethyl cellulose copper nanoparticles (CMC-Cu) investigated in this study have unique and undefined toxicity to Saccharomyces cerevisiae that is different from CuSO4. Cellular surface damage was found in scanning electron micrographs upon CMC-Cu exposure. Further investigation into the lipids revealed altered phosphatidylcholine and phosphatidylethanolamine membrane composition, as well as depleted triacylglycerols, suggesting an impact on the Kennedy lipid pathway. High levels of reactive oxygen species were measured which likely played a role in the lipid peroxidation detected with CMC-Cu treatment. Metal homeostasis was affected by CMC-Cu treatment. The copper sensitive yeast strain, YJM789, significantly decreased cellular zinc concentrations while the copper concentrations increased, suggesting a possible ionic mimicry relationship. In contrast to other compounds that generate ROS, no evidence of genotoxicity was found. As commonplace objects become more integrated with nanotechnology, humanity must look forward past traditional measurements of toxicity.

The Polymorphic PolyQ Tail Protein of the Mediator Complex, Med15, Regulates the Variable Response to Diverse Stresses

The Mediator is composed of multiple subunits conserved from yeast to humans and plays a central role in transcription. The tail components are not required for basal transcription but are required for responses to different stresses. While some stresses are familiar, such as heat, desiccation, and starvation, others are exotic, yet yeast can elicit a successful stress response. 4-Methylcyclohexane methanol (MCHM) is a hydrotrope that induces growth arrest in yeast. We found that a naturally occurring variation in the Med15 allele, a component of the Mediator tail, altered the stress response to many chemicals in addition to MCHM. Med15 contains two polyglutamine repeats (polyQ) of variable lengths that change the gene expression of diverse pathways. The Med15 protein existed in multiple isoforms and its stability was dependent on Ydj1, a protein chaperone. The protein level of Med15 with longer polyQ tracts was lower and turned over faster than the allele with shorter polyQ repeats. MCHM sensitivity via variation of Med15 was regulated by Snf1 in a Myc-tag-dependent manner. Tagging Med15 with Myc altered its function in response to stress. Genetic variation in transcriptional regulators magnified genetic differences in response to environmental changes. These polymorphic control genes were master variators.