The MacroH2A1.1 – PARP1 Axis at the Intersection Between Stress Response and Metabolism

The exchange of replication-coupled canonical histones by histone variants endows chromatin with specific features. The replacement of the canonical H2A histone for the histone variant macroH2A is one of the most remarkable epigenetic modifications. The three vertebrate macroH2A proteins have a unique tripartite structure consisting of H2A-like domain, unstructured linker, and macrodomain. Macrodomains are ancient globular folds that are able to bind nicotinamide adenine dinucleotide (NAD+) derived metabolites. Here, we will briefly describe the physiological relevance of the metabolite binding in the context of chromatin. In particular, we will focus on the macroH2A1.1 isoform that binds ADP-ribose and poly-ADP-ribose polymerase 1 (PARP1) enzyme, a cellular stress sensor. We will discuss the impact of this interaction in the context of cancer, senescence, cell stress and energy metabolism

The Histone Variant MacroH2A1 Regulates Key Genes for Myogenic Cell Fusion in a Splice-Isoform Dependent Manner

Altres ajuts: This research project was supported by the Fundació La Marató de TV3 257/C/2019 (to MB). Research at the IJC is supported by the 'La Caixa' Foundation, the Fundació Internacional Josep Carreras, Celgene Spain.MacroH2A histone variants have functions in differentiation, somatic cell reprogramming and cancer. However, at present, it is not clear how macroH2As affect gene regulation to exert these functions. We have parted from the initial observation that loss of total macroH2A1 led to a change in the morphology of murine myotubes differentiated ex vivo. The fusion of myoblasts to myotubes is a key process in embryonic myogenesis and highly relevant for muscle regeneration after acute or chronic injury. We have focused on this physiological process, to investigate the functions of the two splice isoforms of macroH2A1. Individual perturbation of the two isoforms in myotubes forming in vitro from myogenic C2C12 cells showed an opposing phenotype, with macroH2A1.1 enhancing, and macroH2A1.2 reducing, fusion. Differential regulation of a subset of fusion-related genes encoding components of the extracellular matrix and cell surface receptors for adhesion correlated with these phenotypes. We describe, for the first time, splice isoform-specific phenotypes for the histone variant macroH2A1 in a physiologic process and provide evidence for a novel underlying molecular mechanism of gene regulation

Histone variant MacroH2A1 is downregulated in prostate cancer and influences malignant cell phenotype

Background: Prostate cancer (PCa), a major cause of cancer-related morbidity and mortality worldwide and mostly asymptomatic at earliest stages, is characterized by disruption of genetic and epigenetic balance. A better understanding of how those mechanisms orchestrate disease might improve diagnostic and prognostic tools, allowing for improvements in treatment efficacy. Replacement of canonical histones, an epigenetic mechanism, is highly conserved among species and altered expression of histones variants (e.g., MacroH2A1) has been associated with tumorigenesis. H2AFY gene encodes two isoforms of H2A histone variant MacroH2A1: MacroH2A1.1 and MacroH2A1.2. Specifically, MacroH2A1.1 isoform inhibits cell proliferation and promotes cellular differentiation. Because the contribution of this histone variant to carcinogenesis has been reported in several cancer types, but not for PCa, we aimed to investigate the contribution of MacroH2A1 for prostate carcinogenesis. Methods: MacroH2A1, MacroH2A1.1 and MacroH2A1.2 isoforms and the corresponding splicing regulators transcript levels were evaluated by RT-qPCR, in a tissue cohort composed by PCa, prostatic intraepithelial neoplasia (PIN) and normal prostate cases. Knockdown for MacroH2A1 and MacroH2A1.1 was performed through lentiviral transduction in DU145 cells, and MacroH2A1.1 overexpression was achieved in LNCaP cells by plasmid transfection, followed by functional assays. Biological and/or experimental replicates were performed when necessary, and specific statistical tests were applied to perform data analysis. Results: MacroH2A1.1 transcript levels were downregulated in PIN and primary PCa compared to normal prostate tissues. The same was found for QKI, a MacroH2A1.1's splicing regulator. Moreover, lower MacroH2A1.1 and QKI expression levels associated with less differentiated tumors (Gleason score ≥ 7). Interestingly, MacroH2A1.1, but more impressively DDX17 (AUC = 0.93; p < 0.0001) and QKI (AUC = 0.94; p < 0.0001), accurately discriminated cancerous from noncancerous prostate tissues. Furthermore, in PCa cell lines, total MacroH2A1 knockdown augmented malignant features, whereas MacroH2A1.1 overexpression impressively attenuated the malignant phenotype. Conclusions: Overall, our data, derived from primary PCa tissues and cell lines, anticipate a tumor suppressive role for MacroH2A1, particularly for the MacroH2A1.1 isoform, in prostate carcinogenesis

MacroH2A1.1 regulates mitochondrial respiration by limiting nuclear NAD+ consumption

Histone variants are structural components of eukaryotic chromatin that can replace replication-coupled histones in the nucleosome. The histone variant macroH2A.1.1 contains a macrodomain able to bind NAD+ derived metabolites. Here, we report that macroH2A.1.1 is rapidly induced during myogenic differentiation through a switch in alternative splicing. Importantly, myotubes lacking macroH2A.1.1 display a defect in mitochondrial respiratory capacity. We find that the metabolite-interacting macrodomain is essential for sustaining optimal mitochondrial function, but dispensable for gene regulation. Through direct binding, macroH2A.1.1 inhibits basal poly-ADP ribose polymerase 1 activity and thus reduces nuclear NAD+ consumption. Consequentially, accumulation of the NAD+ precursor NMN allows the maintenance of mitochondrial NAD+ pools critical for respiration. Our data indicate that macroH2A.1.1-containing chromatin regulates mitochondrial respiration by limiting nuclear NAD+ consumption and establishing a buffer of NAD+ precursors in differentiated cells

The Role of macroH2A1 histone variant in muscle metabolism and development

In the eukaryotic nucleus, DNA, wrapped around a core of histone proteins. Replication-coupled histones can be exchanged by histone variants. In mammals, H2A can be replaced by three distinct macroH2A proteins. Alternative splicing of the macroH2A1 transcript further gives rise to macroH2A1.1 and macroH2A1.2 isoforms. We discovered that the expression of macroH2A1 splice isoforms switch during myogenic differentiation. From predominant expression of macroH2A1.2 in proliferating myoblasts to high expression of macroH2A1.1 in differentiated myotubes. This switch has two major consequences. First, both isoforms differentially regulate a number of genes and the dynamics of cell fusion. Second, macroH2A1.1 impacts on cellular metabolism by binding and inhibiting the major nicotinamide adenine dinucleotide-consuming enzyme in the nucleus, the cellular stress sensor PARP1. Finally, we provide evidence that the PARP1 inhibitory capacity of macroH2A is an ancestral function of the protein ranging back to the origins of multicellular life.En el núcleo eucariótico, el ADN se encuentra envuelto alrededor de un núcleo de proteínas histonas. Las histonas acopladas a la replicación pueden intercambiarse por variantes de histonas. La histona H2A puede ser reemplazada por tres proteínas macroH2A distintas. El empalme alternativo de la transcripción de macroH2A1 da lugar a las isoformas macroH2A1.1 y macroH2A1.2. La expresión de las isoformas de empalme macroH2A1 cambia durante la diferenciación miogénica: desde la expresión predominante de macroH2A1.2 en mioblastos en proliferación hasta la expresión alta de macroH2A1.1 en miotubos diferenciados. Este cambio tiene dos consecuencias principales. Primero, ambas isoformas regulan diferencialmente una serie de genes y la dinámica de la fusión celular. En segundo lugar, la macroH2A1.1 tiene un impacto en el metabolismo celular al unirse e inhibir el PARP1, la enzima que consume nicotinamida adenina dinucleótido. Finalmente, proporcionamos evidencia de que la capacidad inhibitoria macroH2A es una función ancestral de la proteína que se remonta a los orígenes de la vida multicelular

The Role of macroH2A1 histone variant in muscle metabolism and development

In the eukaryotic nucleus, DNA, wrapped around a core of histone proteins. Replication-coupled histones can be exchanged by histone variants. In mammals, H2A can be replaced by three distinct macroH2A proteins. Alternative splicing of the macroH2A1 transcript further gives rise to macroH2A1.1 and macroH2A1.2 isoforms. We discovered that the expression of macroH2A1 splice isoforms switch during myogenic differentiation. From predominant expression of macroH2A1.2 in proliferating myoblasts to high expression of macroH2A1.1 in differentiated myotubes. This switch has two major consequences. First, both isoforms differentially regulate a number of genes and the dynamics of cell fusion. Second, macroH2A1.1 impacts on cellular metabolism by binding and inhibiting the major nicotinamide adenine dinucleotide-consuming enzyme in the nucleus, the cellular stress sensor PARP1. Finally, we provide evidence that the PARP1 inhibitory capacity of macroH2A is an ancestral function of the protein ranging back to the origins of multicellular life.En el núcleo eucariótico, el ADN se encuentra envuelto alrededor de un núcleo de proteínas histonas. Las histonas acopladas a la replicación pueden intercambiarse por variantes de histonas. La histona H2A puede ser reemplazada por tres proteínas macroH2A distintas. El empalme alternativo de la transcripción de macroH2A1 da lugar a las isoformas macroH2A1.1 y macroH2A1.2. La expresión de las isoformas de empalme macroH2A1 cambia durante la diferenciación miogénica: desde la expresión predominante de macroH2A1.2 en mioblastos en proliferación hasta la expresión alta de macroH2A1.1 en miotubos diferenciados. Este cambio tiene dos consecuencias principales. Primero, ambas isoformas regulan diferencialmente una serie de genes y la dinámica de la fusión celular. En segundo lugar, la macroH2A1.1 tiene un impacto en el metabolismo celular al unirse e inhibir el PARP1, la enzima que consume nicotinamida adenina dinucleótido. Finalmente, proporcionamos evidencia de que la capacidad inhibitoria macroH2A es una función ancestral de la proteína que se remonta a los orígenes de la vida multicelular

The MacroH2A1.1 - PARP1 Axis at the Intersection Between Stress Response and Metabolism

The exchange of replication-coupled canonical histones by histone variants endows chromatin with specific features. The replacement of the canonical H2A histone for the histone variant macroH2A is one of the most remarkable epigenetic modifications. The three vertebrate macroH2A proteins have a unique tripartite structure consisting of H2A-like domain, unstructured linker, and macrodomain. Macrodomains are ancient globular folds that are able to bind nicotinamide adenine dinucleotide (NAD +) derived metabolites. Here, we will briefly describe the physiological relevance of the metabolite binding in the context of chromatin. In particular, we will focus on the macroH2A1.1 isoform that binds ADP-ribose and poly-ADP-ribose polymerase 1 (PARP1) enzyme, a cellular stress sensor. We will discuss the impact of this interaction in the context of cancer, senescence, cell stress and energy metabolism

The taming of PARP1 and its impact on NAD+ metabolism

Background: Poly-ADP-ribose polymerases (PARPs) are key mediators of cellular stress response. They are intimately linked to cellular metabolism through the consumption of NAD+. PARP1/ARTD1 in the nucleus is the major NAD+ consuming activity and plays a key role in maintaining genomic integrity. Scope of review: In this review, we discuss how different organelles are linked through NAD+ metabolism and how PARP1 activation in the nucleus can impact the function of distant organelles. We discuss how differentiated cells tame PARP1 function by upregulating an endogenous inhibitor, the histone variant macroH2A1.1. Major conclusions: The presence of macroH2A1.1, particularly in differentiated cells, raises the threshold for the activation of PARP1 with consequences for DNA repair, gene transcription, and NAD+ homeostasis.Research in the Ladurner and Buschbeck labs was supported by the following grants: the Deutsche Forschungsgemeinschaft SFB 646 and SFB 1064 collaborative research centers (to AGL); the Deutsche Forschungsgemeinschaft CIPSM and SyNergy research excellence clusters (to AGL); the Bavarian BioSysNet Program (to AGL); the ERA-NET Neuron project Food4Thought funded by the Bundesministerium für Bildung und Forschung (to AGL); the Marie Skłodowska Curie Training network “ChroMe” H2020-MSCA-ITN-2015-675,610 (to MB and AGL); MINECO RTI2018-094005-B-I00 (to MB); MINECO-ISCIII PIE16/00011 (to MB); the Deutsche José Carreras Leukaemie Stiftung DJCLS 14R/2018 (to MB); AGAUR 2017-SGR-305 (to MB); and Fundació La Marató de TV3 257/C/2019 (to MB). Research at the IJC is supported by the La Caixa Foundation, the Fundació Internacional Josep Carreras, Celgene Spain, and the CERCA Program/Generalitat de Catalunya

The taming of PARP1 and its impact on NAD+ metabolism

Altres ajuts: Fundació La Marató de TV3 257/C/2019 (to MB). Research at the IJC is supported by the La Caixa Foundation, the Fundació Internacional Josep Carreras, Celgene Spain.Background: Poly-ADP-ribose polymerases (PARPs) are key mediators of cellular stress response. They are intimately linked to cellular metabolism through the consumption of NAD. PARP1/ARTD1 in the nucleus is the major NAD consuming activity and plays a key role in maintaining genomic integrity. Scope of review: In this review, we discuss how different organelles are linked through NAD metabolism and how PARP1 activation in the nucleus can impact the function of distant organelles. We discuss how differentiated cells tame PARP1 function by upregulating an endogenous inhibitor, the histone variant macroH2A1.1. Major conclusions: The presence of macroH2A1.1, particularly in differentiated cells, raises the threshold for the activation of PARP1 with consequences for DNA repair, gene transcription, and NAD homeostasis