PR002411 (Project)

Description:4-methylcyclohexane methanol (MCHM), an alicyclic alcohol, is a synthetic hydrotrope that induces a starvation response by upregulation of biosynthetic pathways despite the availability of nutrients. To investigate how cellular metabolism can tolerate MCHM, we evolved eight MHCM-resistant strains of S. cerevisiae. To map the SNPs, we resequenced the YJM789 genome with PacBio. We identified thousands of SNPs and indel variants per strain, which was a consistent number between strains that evolved resistance and control strains that remained sensitive. One gene was mutated in all resistant strains. PDR3, controls transcription for the pleiotropic drug response and is the most significant driver of adaptive MCHM resistance in yeast. While many of the evolved alleles of PDR3 would likely produce functional proteins, a knockout in the parent YJM789 strain was sufficient to produce resistance to MCHM. The pdr3 resistance is mediated through Med15, a component of the Mediator complex which regulates activation by transcription factors of RNA Pol II. Pdr3 can homodimerize or dimerize with Pdr1, another transcription factor and loss of Pdr1 also confers MCHM resistance. Normal catabolism of amino acids uses the Pleiotropic Drug Response (PDR) pathway to export breakdown products and loss of pdr3 altered the glutathione and its intermediates. While low levels of ROS are induced by MCHM excess levels of most nitrogen sources rescued MCHM growth. Mutations in PDR3 are first known to increase resistance to this novel hydrotropic chemical.