Hyperoxidation of mitochondrial peroxiredoxin limits H2O2-induced cell death in yeast

Hydrogen peroxide (H2O2) plays important roles in cellular signaling, yet nonetheless is toxic at higher concentrations. Surprisingly, the mechanism(s) of cellular H2O2 toxicity remain poorly understood. Here, we reveal an important role for mitochondrial 1-Cys peroxiredoxin from budding yeast, Prx1, in regulating H2O2-induced cell death. We show that Prx1 efficiently transfers oxidative equivalents from H2O2 to the mitochondrial glutathione pool. Deletion of PRX1 abrogates glutathione oxidation and leads to a cytosolic adaptive response involving upregulation of the catalase, Ctt1. Both of these effects contribute to improved cell viability following an acute H2O2 challenge. By replacing PRX1 with natural and engineered peroxiredoxin variants, we could predictably induce widely differing matrix glutathione responses to H2O2. Therefore, we demonstrated a key role for matrix glutathione oxidation in driving H2O2-induced cell death. Finally, we reveal that hyperoxidation of Prx1 serves as a switch-off mechanism to limit oxidation of matrix glutathione at high H2O2 concentrations. This enables yeast cells to strike a fine balance between H2O2 removal and limitation of matrix glutathione oxidation

Profiling Ssb-Nascent Chain Interactions Reveals Principles of Hsp70-Assisted Folding

The yeast Hsp70 chaperone Ssb interacts with ribosomes and nascent polypeptides to assist protein folding. To reveal its working principle, we determined the nascent chain-binding pattern of Ssb at near-residue resolution by in vivo selective ribosome profiling. Ssb associates broadly with cytosolic, nuclear, and hitherto unknown substrate classes of mitochondrial and endoplasmic reticulum (ER) nascent proteins, supporting its general chaperone function. Ssb engages most substrates by multiple binding-release cycles to a degenerate sequence enriched in positively charged and aromatic amino acids. Timely association with this motif upon emergence at the ribosomal tunnel exit requires ribosome-associated complex (RAC) but not nascent polypeptide-associated complex (NAC). Ribosome footprint densities along orfs reveal faster translation at times of Ssb binding, mainly imposed by biases in mRNA secondary structure, codon usage, and Ssb action. Ssb thus employs substrate-tailored dynamic nascent chain associations to coordinate co-translational protein folding, facilitate accelerated translation, and support membrane targeting of organellar proteins

Hyperoxidation of mitochondrial peroxiredoxin limits H2O2-induced cell death in yeast

Hydrogen peroxide (H2O2) plays important roles in cellular signaling, yet nonetheless is toxic at higher concentrations. Surprisingly, the mechanism(s) of cellular H2O2 toxicity remain poorly understood. Here, we reveal an important role for mitochondrial 1-Cys peroxiredoxin from budding yeast, Prx1, in regulating H2O2-induced cell death. We show that Prx1 efficiently transfers oxidative equivalents from H2O2 to the mitochondrial glutathione pool. Deletion of PRX1 abrogates glutathione oxidation and leads to a cytosolic adaptive response involving upregulation of the catalase, Ctt1. Both of these effects contribute to improved cell viability following an acute H2O2 challenge. By replacing PRX1 with natural and engineered peroxiredoxin variants, we could predictably induce widely differing matrix glutathione responses to H2O2. Therefore, we demonstrated a key role for matrix glutathione oxidation in driving H2O2-induced cell death. Finally, we reveal that hyperoxidation of Prx1 serves as a switch-off mechanism to limit oxidation of matrix glutathione at high H2O2 concentrations. This enables yeast cells to strike a fine balance between H2O2 removal and limitation of matrix glutathione oxidation

Cost-Effective Next Generation Sequencing-Based STR Typing with Improved Analysis of Minor, Degraded and Inhibitor-Containing DNA Samples

Forensic DNA profiles are established by multiplex PCR amplification of a set of highly variable short tandem repeat (STR) loci followed by capillary electrophoresis (CE) as a means to assign alleles to PCR products of differential length. Recently, CE analysis of STR amplicons has been supplemented by high-throughput next generation sequencing (NGS) techniques that are able to detect isoalleles bearing sequence polymorphisms and allow for an improved analysis of degraded DNA. Several such assays have been commercialised and validated for forensic applications. However, these systems are cost-effective only when applied to high numbers of samples. We report here an alternative, cost-efficient shallow-sequence output NGS assay called maSTR assay that, in conjunction with a dedicated bioinformatics pipeline called SNiPSTR, can be implemented with standard NGS instrumentation. In a back-to-back comparison with a CE-based, commercial forensic STR kit, we find that for samples with low DNA content, with mixed DNA from different individuals, or containing PCR inhibitors, the maSTR assay performs equally well, and with degraded DNA is superior to CE-based analysis. Thus, the maSTR assay is a simple, robust and cost-efficient NGS-based STR typing method applicable for human identification in forensic and biomedical contexts