Myc-dependent Mitochondrial Generation of Acetyl-CoA Contributes to Fatty Acid Biosynthesis and Histone Acetylation during Cell Cycle Entry

Fionnuala Morrish,Jhoanna Noonan,Carissa Perez-Olsen,Philip R Gafken,Matthew Fitzgibbon,Joanne Kelleher,Marc Vangilst,David Hockenbery

doi:10.1074/jbc.m110.141606

Abstract

Cell reprogramming from a quiescent to proliferative state requires coordinate activation of multiple -omic networks. These networks activate histones, increase cellular bioenergetics and the synthesis of macromolecules required for cell proliferation. However, mechanisms that coordinate the regulation of these interconnected networks are not fully understood. The oncogene c-Myc (Myc) activates cellular metabolism and global chromatin remodeling. Here we tested for an interconnection between Myc regulation of metabolism and acetylation of histones. Using [(13)C(6)]glucose and a combination of GC/MS and LC/ESI tandem mass spectrometry, we determined the fractional incorporation of (13)C-labeled 2-carbon fragments into the fatty acid palmitate, and acetyl-lysines at the N-terminal tail of histone H4 in myc(-/-) and myc(+/+) Rat1A fibroblasts. Our data demonstrate that Myc increases mitochondrial synthesis of acetyl-CoA, as the de novo synthesis of (13)C-labeled palmitate was increased 2-fold in Myc-expressing cells. Additionally, Myc induced a forty percent increase in (13)C-labeled acetyl-CoA on H4-K16. This is linked to the capacity of Myc to increase mitochondrial production of acetyl-CoA, as we show that mitochondria provide 50% of the acetyl groups on H4-K16. These data point to a key role for Myc in directing the interconnection of -omic networks, and in particular, epigenetic modification of proteins in response to proliferative signals.

Highlights

The oncogene c-Myc (Myc) is a transcription factor with global chromatin remodeling activity
Acetyl groups generated from pyruvate oxidation in mitochondria can be utilized for de novo fatty acid synthesis in the endoplasmic reticulum via citrate export and cleavage by ATP citrate lyase [18]
This shift in fatty acid composition may reflect an increase in de novo fatty acid synthesis as well as increased metabolism of polyunsaturated fatty acids (PUFAs). These results demonstrate that Myc-dependent glucose oxidation during cell cycle entry provides substrates for de novo lipid biosynthesis required for cell division

Summary

EXPERIMENTAL PROCEDURES

Cell Culture—Cells were cultured and harvested as described [11] with a modification in the duration of culture to 8 h to allow pomer spectral analysis; SFA, saturated fatty acid; PUFA, polyunsaturated fatty acid; CID, collision-induced dissociation. Mass Spectrometric Quantification of Acetylation at Specific Lysines within the N-terminal Tail of Histone H4—Histone proteins were isolated from 1 ϫ 108 cells and in vitro labeled as previously described [12]. Elements of x are divided by the D3 intensity to normalize and facilitate comparison across spectra These normalized intensities are used to calculate the percentage of Lys-16 acetylation from any given source (in vitro, acetate and glucose), total acetylation, and unacetylation. Fractional contribution of 13C-labeled carbon sources to fatty acid synthesis, D, and fractional new synthesis of fatty acids during time t, g(t), were estimated from the mass isotopomer distribution of palmitate based on the model of ISA as previously reported [17]. All experiments were performed at least three times, and statistical analysis of comparisons between mycϪ/Ϫ and mycϩ/ϩ samples was conducted using Student’s t test

RESULTS

Superimposed on this pattern is the

DISCUSSION

ADDITIONS AND CORRECTIONS