Hat1-Dependent Lysine Acetylation Targets Diverse Cellular Functions

Lysine acetylation has emerged as one of the most important post-translational modifications, regulating different biological processes. However, its regulation by lysine acetyltransferases is still unclear in most cases. Hat1 is a lysine acetyltransferase originally identified based on its ability to acetylate histones. Using an unbiased proteomics approach, we have determined how loss of Hat1 affects the mammalian acetylome. Hat1+/+ and Hat1-/- mouse embryonic fibroblast (MEF) cells lines were grown in both glucose- and galactose-containing media, as Hat1 is required for growth on galactose due to defects in mitochondrial function. Following trypsin digestion of whole cell extracts, acetylated peptides were enriched by acetyllysine affinity purification and acetylated peptides were identified and analyzed by label-free quantitation. Comparison of the acetylome from Hat1+/+ cells grown on galactose and glucose demonstrated that there are large carbon source-dependent changes in the mammalian acetylome where the acetylation of enzymes involved in glycolysis was the most affected. Comparisons of the acetylomes from Hat1+/+ and Hat1-/- cells identified 65 proteins whose acetylation decreased by at least 2.5-fold in cells lacking Hat1. In Hat1-/- cells, acetylation of the auto regulatory loop of CBP was the most highly affected, decreasing by up to 20-fold. In addition to proteins involved in chromatin structure, Hat1-dependent acetylation was also found in a number of transcriptional regulators, including p53, and mitochondrial proteins. Hat1 mitochondrial localization suggests that it may be directly involved in the acetylation of mitochondrial proteins.