The effect of accumulation of a Cit1 mutant that lacks presequence in Saccharomyces cerevisiae

Deficiencies in mitochondrial protein import are associated with a number of diseases. However, although non-imported mitochondrial proteins are at great risk of aggregation, it remains largely unclear how their accumulation causes cell dysfunction. In this study, we found that citrate synthase (Cit1) mutant that lacks the N-terminal mitochondrial targeting sequence, which we call here NdeltaCit1, is localized in the cytosol and is targeted for proteasomal degradation by the ubiquitin ligase SCFUcc1. Intriguingly, NdeltaCit1 is soluble in the cytosol and exhibits enzymatic activity. To analyze the cellular consequence of the accumulation of NdeltaCit1, we created a NdeltaCit1 mutant that escapes SCFUcc1-mediated degradation (NdeltaCit1-DS/AA). We also created a mutant that lacks the catalytic activity (NdeltaCit1-DS/AA-H/G). We performed an RNA sequence analysis and compared the gene expression profile of wild-type cells expressing NdeltaCit1-DS/AA or NdeltaCit1-DS/AA-H/G under the control of the GAL1 promoter. Comparative gene expression profiling analysis of RNA-seq data for cells expressing NdeltaCit1-DS/AA or NdeltaCit1-DS/AA-H/G.