Intermediary Metabolism, Histone Acetylation, and Transcriptional Regulation

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DESCRIPTION (provided by applicant): The long-term goal of our laboratory is to understand how intermediary metabolism affects histone acetylation and transcriptional regulation and to utilize this information to develop novel strategies for cancer treatment. Histone acetylation is a dynamic modification that affects chromatin structure and regulates diverse cellular functions, such as gene expression, DNA repair, and cell proliferation. Perturbation of the balanced action of histone acetyltransferases (HATs) and histone deacetylases (HDACs) alters the expression pattern of genes involved in cellular growth, resulting in tumorigenesis. On the other hand, many HDAC inhibitors reactivate the transcription of multiple genes that are silenced in cancer and thus possess anti-cancer activity. Histone acetylation depends on intermediary metabolism for supplying acetyl-CoA in the nucleocytosolic compartment. In budding yeast, acetyl-CoA is generated by the glycolytic pathway. Our previous studies revealed that the synthesis of acetyl-CoA via the glycolytic pathway, and subsequently histone acetylation, are significantly reduced in cells with mutation of phospholipase C (PLC1). Since nucleocytosolic acetyl-CoA is also used for de novo synthesis of fatty acids, histone acetylation and the synthesis of fatty acids compete for the same acetyl-CoA pool. The first and rate-limiting reaction in de novo synthesis of fatty acids is carboxylation of acetyl-CoA to form malonyl-CoA, catalyzed by acetyl-CoA carboxylase (ACC). We have shown that attenuated expression of ACC in yeast cells results in increased histone acetylation and altered transcriptional regulation, implicating ACC as a regulatory link between intermediary metabolism and histone acetylation. The central hypothesis of this proposal, based on our preliminary data, is that regulation of glucose uptake, glycolysis, and ACC affect homeostasis of acetyl-CoA and consequently histone acetylation and transcriptional regulation. Since orthologs Snf1 in yeast cells and AMP-activated protein kinase (AMPK) in mammalian cells phosphorylate and inhibit ACC, the Aim 1 of this proposal addresses whether Snf1 and AMPK regulate histone acetylation in yeast and mammalian cells, respectively. We will also determine whether the inhibition of ACC or the activation of AMPK in human breast cancer MCF7 cells results in increased acetylation of histones, altered transcriptional regulation, and increased apoptosis. In Aim 2, we will test the hypothesis that the histone hypoacetylation in the plc1 cells is due to the defect in glucose transport and metabolism caused by the failure to degrade transcriptional repressor Mth1 by the ubiquitin-proteasome pathway. The approach presented in this proposal is based on the previously underappreciated relationship between intermediary metabolism and histone acetylation and will test a novel concept for the development of cancer therapy aimed at redirecting acetyl-CoA from lipid synthesis to histone acetylation, thus altering transcriptional regulation and inducing apoptosis. In addition, this project will provide an excellent research environment for undergraduate and graduate students, as they prepare for careers in biomedical research.