Figure 6: Isoleucine is a major substrate for nuclear propionyl-CoA generation and histone lysine propionylation.
A) Propionyl-CoA is generated in the mitochondria from multiple sources including isoleucine and valine. 3 of the 6 carbons in isoleucine contribute to the acyl group of propionyl-CoA. B) Incorporation of various substrates into propionyl-CoA M3 was compared in whole cells by direct extraction of HepG2, HeLa and pancreatic adenocarcinoma (KPC) cells incubated in serum free media containing uniformly (U) 13C-labeled substrates for 18 h. C) Incorporation of 13C6-isoleucine into propionyl-CoA M3 in KPC cells incubated in serum free media containing 13C6-isoleucine diluted 1:1 with unlabeled isoleucine for the indicated times with post-labeling to account for post-harvest metabolism. D) Histone lysine propionylation reaction catalyzed by histone acyl transferase (HAT) enzymes. E) 13C6-isoleucine incorporation into 13C3-Kpr marks determined by histone acyl proteomic analysis of HepG2 cells incubated in DMEM supplemented with 10% dialyzed FBS in which unlabelled isoleucine was entirely replaced for the indicated times. For all experiments, n=3 replicate samples per condition from a single experiment. Error bars are standard deviation. p < 0.05 (*), p < 0.01 (**).