Abstract
The modulation of dynamic histone acetylation states is key for organizing chromatin structure and modulating gene expression and is regulated by histone acetyltransferase (HAT) and histone deacetylase (HDAC) enzymes. The mammalian SIRT6 protein, a member of the Class III HDAC Sirtuin family of NAD+-dependent enzymes, plays pivotal roles in aging, metabolism, and cancer biology. Through its site-specific histone deacetylation activity, SIRT6 promotes chromatin silencing and transcriptional regulation of aging-associated, metabolic, and tumor suppressive gene expression programs. ATP citrate lyase (ACLY) is a nucleo-cytoplasmic enzyme that produces acetyl coenzyme A (acetyl-CoA), which is the required acetyl donor for lysine acetylation by HATs. In addition to playing a central role in generating cytosolic acetyl-CoA for de novo lipogenesis, a growing body of work indicates that ACLY also functions in the nucleus where it contributes to the nutrient-sensitive regulation of nuclear acetyl-CoA availability for histone acetylation in cancer cells. In this study, we have identified a novel function of SIRT6 in controlling nuclear levels of ACLY and ACLY-dependent tumor suppressive gene regulation. The inactivation of SIRT6 in cancer cells leads to the accumulation of nuclear ACLY protein and increases nuclear acetyl-CoA pools, which in turn drive locus-specific histone acetylation and the expression of cancer cell adhesion and migration genes that promote tumor invasiveness. Our findings uncover a novel mechanism of SIRT6 in suppressing invasive cancer cell phenotypes and identify acetyl-CoA responsive cell migration and adhesion genes as downstream targets of SIRT6.
Highlights
Acetyl-coenzyme A is a key metabolic intermediate that links the metabolism, signaling, and epigenetics
We show that SIRT6 deficiency increases the nuclear ATP citrate lyase (ACLY) protein, nuclear acetyl-CoA abundance, and locus-specific histone acetylation, which in turn drive an up-regulation of Platelet Derived Growth Factor Receptor A (PDGFRA) and other genes that contribute to invasive cancer cell adhesion and migration phenotypes
We have characterized a functional interaction between SIRT6 and ACLY which plays essential roles in modulating nuclear acetyl-CoA abundance, locus-specific histone acetylation, and the expression of cancer cell adhesion and migration genes
Summary
Acetyl-coenzyme A (acetyl-CoA) is a key metabolic intermediate that links the metabolism, signaling, and epigenetics. It is the acetyl donor for protein acetylation reactions, including histone lysine acetylation, which play important roles in chromatin dynamics and gene regulation [1,2,3]. Two nucleo-cytoplasmic enzymes have been reported to play key roles in maintaining nuclear acetyl-CoA abundance: acetyl-CoA synthetase 2 (ACSS2), which converts acetate to acetyl-CoA and directly regulates histone acetylation in differentiating neurons [12,13]; and ATP citrate lyase (ACLY), which catalyzes the conversion of citrate to oxaloacetate and acetyl-CoA [11,14]. ACLY-mediated nuclear acetyl-CoA production was only recently shown to be an important mechanism in controlling HAT-dependent histone acetylation, which impacts specific gene expression profiles during tumorigenesis [16,17,18,19], highlighting the role of ACLY as an important epigenetic regulator
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