Superfund Research Program

Comparative and Functional Genomics Analysis of Superfund Toxicants

Project Leader: Paul Russell (The Scripps Research Institute)
Grant Number: P42ES010337
Funding Period: 2000-2017

Project-Specific Links

Final Progress Reports

Year:   2016  2009  2004 

Cadmium (Cd) and arsenic (As) are amongst the most common environmental pollutants found at Superfund sites. Dr. Russell’s group is using both classical genetics and systems biology approaches to determine how eukaryotic organisms cope with exposure to these environmental toxins. These investigations are being carried out with the fission yeast Schizosaccharomyces pombe, which is an experimentally amenable microorganism that is a useful model for studies of stress response mechanisms that are conserved in other eukaryotic organisms, including mammals and plants. To identify novel genes involved in As/Cd detoxification, researchers screened a random insertional mutagenesis library of S. pombe for mutants that are hypersensitive to As/Cd. Mutations were mapped to spc1⁺ (sty1⁺), a stress-activated protein kinase orthologous to human p38, or SPBC17G9.08c. SPBC17G9.08c/Cnt5 is a member of the Centaurin Arf GAP protein family found in a variety of fungi, plants and metazoans, but not in Saccharomyces cerevisiae. The function of Centaurin proteins is unknown and these are the first data linking them to heavy metal resistance. Researchers biochemical and microscopic studies suggest that Cnt5 contributes to As/Cd resistance by maintaining membrane integrity or by modulating membrane trafficking (Vashisht et al., 2009). Last year researchers described a high-throughput screen of ~3,000 haploid mutants, each deleted for a single non-essential gene, in which researchers identified over 200 genes that are required for robust resistance to cadmium (Kennedy et al., 2008). Researchers have expanded this screen to arsenic in which researchers have identified a similar number of genes, some of which overlap with those required for Cd resistance. Many of these genes were not previously known to be involved in arsenic resistance. Researchers are integrating these findings with high-density microarray analysis of gene expression in wild type, spc1 mutant, or zip1 mutant cells exposed to arsenic. Zip1 is a transcription factor that regulates gene expression in response to some types of cytotoxic stress. About half of the ~600 up-regulated genes are a part of the CESR (common environmental stress response) that are typically induced in response to oxidative stress. The Spc1 MAPK pathway regulates many of these genes. Zip1 regulates about 80 of the genes. Zip1 gene regulation is largely independent of Spc1. A surprising number of the induced genes are related to ubiquitin-dependent mechanisms, suggesting a critical and unexpected role for this form of post-translational regulation in mediating cellular responses to arsenic exposure. In addition to these studies, continuing collaboration with Dr. Schroeder’s lab is to understand the cadmium detoxification pathway involving phytochelatin (PC) in fission yeast, as a model for heavy metal detoxification in plants. Our current studies are narrowing down a family of ABC transporters that are important for sequestering Cd-PC complexes in vacuoles. Defining these transporters may be critical for improving plant-mediated bioremediation of cadmium and other heavy metals at Superfund sites.