Identifying Novel Factors Involved In Yeast Mitochondrial Protein Synthesis

Abstract

The goal of our work is to identify protein factors involved in the initiation of mitochondrial translation using yeast genetics. FMT1 encodes the S. cerevisiae methionyl‐tRNA formyltransferase, which catalyzes the formylation of mitochondrial initiator Met‐tRNA. A genetic screen was performed with an fmt1 deletion strain to generate synthetic petite strains – strains containing mutations that in combination with the fmt1 deletion lead to the loss of respiratory growth. One mutant strain, s.p. 72–1, was transformed with a yeast genomic DNA library to identify open reading frames that complement the respiratory‐deficient phenotype. A region of chromosome XVI, including the LPE10 gene, was found to rescue growth on non‐fermentable carbon sources. Sequencing of DNA from the mutant strain revealed that the LPE10 gene, encoding a mitochondrial inner membrane magnesium transporter, contained a point mutation leading to a premature stop codon. This mutation likely causes the synthetic petite phenotype with the deletion of fmt1. Indeed, an lpe10 fmt1 double mutant has a more severe respiratory growth defect than the single lpe10 deletion strain. Deletion of the MIS1 gene, also required for the formylation of mitochondrial initiator tRNA, also leads to the petite phenotype in combination with the lpe10 deletion. This work is supported by HHMI and NSF grants to the Freshman Research Initiative at UT‐Austin.