Genetic Screen for Suppressors of Y east Coq8 Mutants

Abstract

Coenzyme Q (Q) is a lipid electron and proton carrier in the electron transport chain. Q functions in mitochondrial respiratory chain and serves as a lipophilic antioxidant. In yeast Saccharomyces cerevisiae, eleven genes designated as COQ1 through COQ9, YAH1 and ARH1, have been identified as being required for coenzyme Q biosynthesis. One of these eleven genes, COQ8, encodes Coq8 and previous studies suggest that Coq8 may function as a kinase required for Q biosynthesis. However, no experiments have yet shown any explicit kinase activity of Coq8 nor have phosphorylated forms of the Coq8 polypeptide been detected. Our goal in this project was to isolate coq8-3 revertants that can correct the Q biosynthetic defect and to perform genetic screens to identify novel protein suppressors present in the coq8-3 mutant. Both coq8-3 and coq8 null mutant lack Q6 and neither can grow on rich medium containing glycerol (YPG), a nonfermentable carbon source. Our results show that after 14 days of incubation, small yeast revertants were observed among the coq8-3 mutants plated on YPG plates. These revertants retain the original mutation present in the coq8-3 parent strain, but can grow in medium containing nonfermentable carbon sources. Ten coq8-3 revertants will further be analyzed and we hope to determine whether these revertants contain potential suppressor genes. It is our goal to identify any compensatory mutations that might help characterize Coq8 function. By understanding the kinase function of Coq8, this study will help us elucidate the eukaryotic biosynthetic pathway of Q, which is central to understanding and unraveling human genetic diseases related to Q deficiencies This research was supported by NSF MCB-1330803 and by NIH GM55052.