Heart failure drug proscillaridin A targets MYC overexpressing leukemia through global loss of lysine acetylation.

BACKGROUND: Cardiac glycosides are approved for the treatment of heart failure as Na+/K+ pump inhibitors. Their repurposing in oncology is currently investigated in preclinical and clinical studies. However, the identification of a specific cancer type defined by a molecular signature to design targeted clinical trials with cardiac glycosides remains to be characterized. Here, we demonstrate that cardiac glycoside proscillaridin A specifically targets MYC overexpressing leukemia cells and leukemia stem cells by causing MYC degradation, epigenetic reprogramming and leukemia differentiation through loss of lysine acetylation. METHODS: Proscillaridin A anticancer activity was investigated against a panel of human leukemia and solid tumor cell lines with different MYC expression levels, overexpression in vitro systems and leukemia stem cells. RNA-sequencing and differentiation studies were used to characterize transcriptional and phenotypic changes. Drug-induced epigenetic changes were studied by chromatin post-translational modification analysis, expression of chromatin regulators, chromatin immunoprecipitation, and mass-spectrometry. RESULTS: At a clinically relevant dose, proscillaridin A rapidly altered MYC protein half-life causing MYC degradation and growth inhibition. Transcriptomic profile of leukemic cells after treatment showed a downregulation of genes involved in MYC pathways, cell replication and an upregulation of hematopoietic differentiation genes. Functional studies confirmed cell cycle inhibition and the onset of leukemia differentiation even after drug removal. Proscillaridin A induced a significant loss of lysine acetylation in histone H3 (at lysine 9, 14, 18 and 27) and in non-histone proteins such as MYC itself, MYC target proteins, and a series of histone acetylation regulators. Global loss of acetylation correlated with the rapid downregulation of histone acetyltransferases. Importantly, proscillaridin A demonstrated anticancer activity against lymphoid and myeloid stem cell populations characterized by MYC overexpression. CONCLUSION: Overall, these results strongly support the repurposing of proscillaridin A in MYC overexpressing leukemia.

SIRT3 controls brown fat thermogenesis by deacetylation regulation of pathways upstream of UCP1.

OBJECTIVE: Brown adipose tissue (BAT) is important for thermoregulation in many mammals. Uncoupling protein 1 (UCP1) is the critical regulator of thermogenesis in BAT. Here we aimed to investigate the deacetylation control of BAT and to investigate a possible functional connection between UCP1 and sirtuin 3 (SIRT3), the master mitochondrial lysine deacetylase. METHODS: We carried out physiological, molecular, and proteomic analyses of BAT from wild-type and Sirt3KO mice when BAT is activated. Mice were either cold exposed for 2 days or were injected with the ß3-adrenergic agonist, CL316,243 (1 mg/kg; i.p.). Mutagenesis studies were conducted in a cellular model to assess the impact of acetylation lysine sites on UCP1 function. Cardiac punctures were collected for proteomic analysis of blood acylcarnitines. Isolated mitochondria were used for functional analysis of OXPHOS proteins. RESULTS: Our findings showed that SIRT3 absence in mice resulted in impaired BAT lipid use, whole body thermoregulation, and respiration in BAT mitochondria, without affecting UCP1 expression. Acetylome profiling of BAT mitochondria revealed that SIRT3 regulates acetylation status of many BAT mitochondrial proteins including UCP1 and crucial upstream proteins. Mutagenesis work in cells suggested that UCP1 activity was independent of direct SIRT3-regulated lysine acetylation. However, SIRT3 impacted BAT mitochondrial proteins activities of acylcarnitine metabolism and specific electron transport chain complexes, CI and CII. CONCLUSIONS: Our data highlight that SIRT3 likely controls BAT thermogenesis indirectly by targeting pathways upstream of UCP1.

Nonhistone targets of KAT2A and KAT2B implicated in cancer biology 1.

Lysine acetylation is a critical post-translation modification that can impact a protein's localization, stability, and function. Originally thought to only occur on histones, we now know thousands of nonhistone proteins are also acetylated. In conjunction with many other proteins, lysine acetyltransferases (KATs) are incorporated into large protein complexes that carry out these modifications. In this review we focus on the contribution of two KATs, KAT2A and KAT2B, and their potential roles in the development and progression of cancer. Systems biology demands that we take a broad look at protein function rather than focusing on individual pathways or targets. As such, in this review we examine KAT2A/2B-directed nonhistone protein acetylations in cancer in the context of the 10 "Hallmarks of Cancer", as defined by Hanahan and Weinberg. By focusing on specific examples of KAT2A/2B-directed acetylations with well-defined mechanisms or strong links to a cancer phenotype, we aim to reinforce the complex role that these enzymes play in cancer biology.

A Screen for Candidate Targets of Lysine Polyphosphorylation Uncovers a Conserved Network Implicated in Ribosome Biogenesis.

Polyphosphates (polyP) are chains of inorganic phosphates found in all cells. Previous work has implicated these chains in diverse functions, but the mechanism of action is unclear. A recent study reports that polyP can be non-enzymatically and covalently attached to lysine residues on yeast proteins Nsr1 and Top1. One question emerging from this work is whether so-called "polyphosphorylation" is unique to these proteins or instead functions as a global regulator akin to other lysine post-translational modifications. Here, we present the results of a screen for polyphosphorylated proteins in yeast. We uncovered 15 targets including a conserved network of proteins functioning in ribosome biogenesis. Multiple genes contribute to polyphosphorylation of targets by regulating polyP synthesis, and disruption of this synthesis results in translation defects as measured by polysome profiling. Finally, we identify 6 human proteins that can be modified by polyP, highlighting the therapeutic potential of manipulating polyphosphorylation in vivo.