Defining Roles of the Yeast Lysine Acetyltransferase NuA4 in Metabolism

Abstract

The yeast lysine acetyltransferase complex NuA4 was initially described to target histone H4 for acetylation but since then many non-histone targets of NuA4 have been identified, a surprising number of which have been implicated in metabolic control. Here we use functional genomics, chemogenetics, high content microscopy and phenotype analysis combined with secondary analysis to discover and investigate novel roles of NuA4 in metabolic control in the Saccharomyces cerevisiae model system. In my first study, I screened 368 GFP-tagged metabolic proteins and identified 23 as high confidence hits for a change in localization or abundance upon deletion of EAF1, a key scaffolding member of the NuA4 complex. Top hits from the screen identified changes in the localization/abundance of glycogen synthesis and mitochondrial proteins in the eaf1Δ yeast. Targeted investigation of these phenotypes led to us characterize a NuA4 dependent regulation of the localization of Bcy1, the regulatory subunit of yeast PKA. The proposed acetylation of Bcy1 affected PKA activity downstream regulating mitochondrial dynamics and glycogen synthesis. The second study stemmed from our identification of a change in the localization of Acc1, the enzyme catalyzing the first step in de novo lipid synthesis, upon deletion of EAF1. The modulation of a protein in lipid synthesis prompted an investigation into NuA4 dependent lipid regulation, specifically investigating a role for NuA4 in regulating ergosterol dynamics. The eaf1Δ yeast are more sensitive to drugs targeting ergosterol and ergosterol biosynthesis, have increased staining with filipin, contain more ergosterol biosynthesis intermediates, and have more lipid droplets than WT yeast cells, suggesting an increase in both ergosteryl esters and free ergosterol in eaf1∆ cells. A chemical genomic screen identified ERG3, POT1, GAL83, GIP3, and AFR1 as gene deletions which reverse the eaf1Δ dependent increase in ergosterol. As NuA4 and its catalytic subunit Esa1 are highly conserved to Tip60, a lysine acetyltransferase commonly deregulated in human disease, our research showing metabolic control in yeast may have implications in understanding metabolic deregulation in association with alterations in Tip60 activity in disease.