Project description:SIRT1 is a nuclear NAD+-dependent protein deacetylase. Expression microarray analysis was used to study the effect of SIRT1 knockdown on gene expression in MCF-7 breast cancer cells. Experiment Overall Design: SIRT1 stable knockdown was achieved using two retroviral shRNA constructs. An shRNA directed against Luciferase was used to generate the Luc control cells. Three independent biological replicates with matching Luc controls were analyzed using Affymetrix U133A 2.0 microarrays. Experiment Overall Design: These 6 samples were part of a 15-sample microarray analysis (GSE12971) examining expression regulation by SIRT1, PARP-1, PARG and macroH2A. All 15 samples were included for the following data normalization steps: data sets obtained using the GCOS software were grouped based on date of experiment and adjusted for batch effect using the parametric empirical Bayes method (Combat R); all values < 0.01 were adjusted to 0.01; the data were log2 transformed, median centered for each array, and median centered for each gene.
Project description:In mammals, nicotinamide phosphoribosyltransferase (NAMPT) and nicotinamide mononucleotide adenylyltransferase 1 (NMNAT-1) constitute a nuclear NAD+ salvage pathway, regulating cellular functions of the NAD+-dependent deacetylase SIRT1. However, little is known about the molecular mechanisms by which NAD+ biosynthesis controls gene transcription in the nucleus. In this study, we show that stable knockdown of NAMPT or NMNAT-1 in MCF-7 breast cancer cells significantly reduced total cellular NAD+ levels. Expression microarray analyses demonstrate that both enzymes have broad and overlapping functions in gene regulation. SIRT1 is a key mediator of NAMPT- and NMNAT-1-dependent gene regulation, and is found at promoters of many of the target genes. Furthermore, SIRT1 deacetylase activity at these promoters is regulated by NAMPT and NMNAT-1. Most significantly, NMNAT-1 interacts with SIRT1 and is recruited to target gene promoters by SIRT1. Our results reveal an unexpected mechanism for the direct control of SIRT1 deacetylase activity at target gene promoters by NMNAT-1. Interactions between NMNAT-1 and SIRT1 at gene promoters may provide a platform for integration of multiple signaling pathways that regulate transcription. This SuperSeries is composed of the SubSeries listed below.
Project description:SIRT1 is a nuclear NAD+-dependent protein deacetylase. Expression microarray analysis was used to study the effect of SIRT1 knockdown on gene expression in MCF-7 breast cancer cells.
Project description:SIRT1 is a NAD+-dependent protein deacetylase. SIRT1 plays key roles in metabolic regulation and adaptation. In this study, we examined the difference of gene expression in brown adipose tissue from WT and SIRT1tg mice.
Project description:SIRT1 is a NAD+-dependent protein deacetylase. SIRT1 plays key roles in metabolic regulation and adaptation. In this study, we wanted to compare gene expression profile in SIRT1 overexpressing mice to WT mice submitted to different intervention (caloric restriction and exercise training) in different tissues (liver, skeletal muscle, brown and white adipose tissues).
Project description:The goal of this project is to investigate the role of SIRT1, the most conserved mammalian NAD+-dependent protein deacetylase, in the regulation of heart development. SIRT1 is important for heart development and functions. However, the underlying molecular mechanisms remain undefined. In this study, we analyzed the gene expression profiles in E18.5 WT and SIRT1 KO mouse hearts.
Project description:The Sirtuin family of NAD+-dependent enzymes play an important role in the maintenance of genome stability upon stress. Several mammalian Sirtuins have been linked directly or indirectly to the regulation of DNA damage during replication through Homologous recombination (HR). The role of one of them, SIRT1, is intriguing as it seems to have a general regulatory role in DNA damage response (DDR) that has not been addressed. SIRT1-deficient cells show impairment of DDR reflected in a decrease in repair capacity, increased genome instability and decreased levels of H2AX. Here we unveil a close functional antagonism between SIRT1 and the PP4 phosphatase multiprotein complex in the regulation of DDR. Upon DNA damage SIRT1 interacts specifically with PP4C and promotes its inhibition through deacetylation of the domain WH1 of the PP4R3/ regulatory subunits. This in turn, regulates H2AX signal and RPA2 phosphorylation, two key events in the signaling of DNA damage and repair by HR. We propose a mechanism whereby during stress SIRT1 signaling ensures a global control of DNA damage through PP4.
Project description:SIRT1 is a NAD+-dependent protein deacetylase. SIRT1 plays key roles in metabolic regulation and adaptation. In this study, we examined the difference of gene expression in brown adipose tissue from WT and SIRT1tg mice. SIRT1 transgenic model (heterozygous transgenic model) has already been described (Pfluger et al., 2008). Here we used homozygote transgenic mice which had been backcrossed to C57Bl/6N background. 3 months old WT and SIRT1tg mice were fed with a low fat diet. After sacrifice, total mRNA obtained from brown adipose were used for microarray.
Project description:SIRT1 is a nuclear enzyme that removes acetyl-groups from target proteins by using NAD+ as a co-substrate. SIRT1 regulates many vital biological processes such as metabolism, stress response, development, and aging. We have previously shown that SIRT1 is critically involved in mouse embryonic stem cell (mESC) maintenance and differentiation in part through modulation of the acetylation status of key transcription factors and their mediated amino acid metabolism and cell signaling. Recent reports have shown that a number of alternative splicing factors are deacetylation substrates of SIRT1. In this study, we aim to understand the total RNA transcriptome, including splicing landscapes, of WT and SIRT1 KO mESCs.
Project description:Ataxia-telangiectasia (A-T) is a disease characterized by genomic instability and severe neurodegeneration. It is caused by mutation in Ataxia-telangiectasia mutated gene (ATM) which encodes ATM, a key player in DNA double-strand break (DSB) repair. While many major symptoms of A-T (including hypersensitivity to ionizing radiation) are readily explained by its deficiency in repair of DSBs, the causes for the devastating cerebellar degeneration are still elusive. Here we report that in A-T, persistent unrepaired DNA damage signals from the nucleus to mitochondria (NM signaling) causing mitochondrial dysfunction leading to neurodegeneration. We find that depletion of NAD+ in A-T across species is likely due to persistent PARylation as inhibition of PARP1 restores NAD+levels.. NAD+ depletion affects the NAD+/SIRT1-PGC1α axis causing accumulation of damaged mitochondria through inhibition of mitophagy. Restoration of NAD+/SIRT1 activity through PARP1 inhibition, NAD+ supplementation or SIRT1 activation rescued the pathological and behavioral defects in A-T, suggesting a conserved role of the NAD+/SIRT1 pathway in inhibiting disease pathology. Notably, increasing the NAD+ levels extends lifespan and rescues A-T-specific behavioral defects in both C. elegans and mouse models of A-T. This is through induction of PINK1-DCT1-regulated mitophagy and DNA-PKcs-associated NHEJ DNA repair. Our results underscore the unified role of SIRT1 (Sir2.1) in mitochondrial health and highlight how Sir2.1 not only regulates mitochondrial biogenesis, but also induces PINK1-DCT1-dependent mitophagy. Our data support a model where by the two major theories on aging, DNA damage accumulation and mitochondrial dysfunction, conspire to promote neurodegeneration in A-T animal models and suggest that therapeutic interventions are possible in A-T and other untreatable DNA repair-deficient disorders.