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LARP7 ameliorates cellular senescence and aging-related atherosclerosis by allosterically enhancing SIRT1 deacetylase activity

ABSTRACT: Cell senescence is a cell state characterized with permanent cell cycle arrest and elevated proinflammatory secretome and associated with pleiotropic essential physiopathological processes. The persistent DNA damage response (DDR) is the major stress leading to senescence, however the molecular mechanism underling remains elusive. Here, we identified the La Ribonucleoprotein 7 (LARP7), a 7SK RNA binding protein, as a novel SIRT1 deacetylase activator. It directly interacted with SIRT1 allosteric regulatory domain and enhanced its deacetylase activity. DDR-mediated ATM activation trigged the extracellular shuttling and downregulation of LARP7 that dampened the SIRT1 deacetylase activity and enhanced p53 and NFB (p65) transcriptional activity by augmenting their acetylation. As a consequence, activated p53 and NFB arrested cell growth and promoted SASP genes expression, and thereby accelerated the cellular senescence. Inducible deletion of LARP7 in wildtype mouse led to senescent cell accumulation and premature ageing. Furthermore, we identified that ATM-LARP7-SIRT1-p53/NFB senescent axis was active in the aortic senescence and atherogenesis. Genetic depletion of LARP7 aggravated the atherogenesis but conversely, inhibited ATM activation or restoring LARP7 expression with genetic manipulation alleviated the vascular aging and atherogenesis. Together, this study identifies LARP7 as a novel SIRT1 cellular activator and it’s-mediated ATM-LARP7-SIRT1-p53/NFB axis is attributed to DDR-mediated cellular senescence and aging-related pathologies.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE160279 | GEO | 2021/10/30

REPOSITORIES: GEO

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Project description:Activation of the MLL-ENL-ERtm oncogene initiates aberrant proliferation of myeloid progenitors. Here, we show induction of a fail-safe mechanism mediated by the DNA damage response (DDR) machinery that results in activation of the ATR/ATM-Chk1/Chk2-p53/p21 checkpoint and cellular senescence at early stages of cellular transformation caused by a regulatable MLL-ENL-ERtm in mice. Furthermore, we identified the transcription program underlying this intrinsic anti-cancer barrier, and DDR-induced inflammatory regulators that fine-tune the signaling towards senescence, thereby modulating the fate of MLL-ENL-immortalized cells in a tissue-environment-dependent manner. Our results indicate that DDR is a rate-limiting event for acquisition of stem cell-like properties in MLL-ENL-ERtm-mediated transformation, as experimental inhibition of the barrier accelerated the transition to immature cell states and acute leukemia development. We created a mouse model wherein the protein function of the MLL-ENL oncogene depends on tamoxifen due to fusion with the mutated estrogen-binding domain of the estrogen receptor (ERtm). After 7 months of tamoxifen administration, the MLL-ENL-ERtm mice developed a myeloproliferative disease, which progressed into the terminal stage after a long period (mean survival: 592 ± 112 days) of continuous tamoxifen provision. We have profiled gene expression at three time-points of tamoxifen treatment corresponding to three distinct cellular states of the MLL-ENL-ERtm-induced myeloproliferation in the bone marrow: 1. 7 months - high proliferation state with low DDR signaling (4 biological replicates), 2. 7-8 months - the transition period of lower proliferation and high DDR activity (4 biogical replicates) and 3. 8 months - the senescence (3 biological replicates). Time-matched tamoxifen-treated wild-type bone marrow analysed in 4 biological replicates. We have profiled gene expression in three disease stages in the spleen: 1. 7 months - early stage - induced proliferation and DDR (3 biological replicates), 2. 9-10 months - progression - partial senescence and DDR is maintained (3 biological replicates) and 3. 16-23 months - terminal stage - proliferation, low or absent DDR and no senescence (3 biological replicates). Time-matched tamoxifen-treated and age-matched wild-type spleens analysed in 5 biological replicates.

Project description:This is the model described in: Feedback between p21 and reactive oxygen production is necessary for cell senescence. Passos JF, Nelson G, Wang C, Richter T, Simillion C, Proctor CJ, Miwa S, Olijslagers S, Hallinan J, Wipat A, Saretzki G, Rudolph KL, Kirkwood TB, von Zglinicki T. ;Mol Sys Biol2010;6:347. Epub 2010 Feb 16. PMID:20160708 doi:10.1038/msb.2010.5; Abstract: Cellular senescence--the permanent arrest of cycling in normally proliferating cells such as fibroblasts--contributes both to age-related loss of mammalian tissue homeostasis and acts as a tumour suppressor mechanism. The pathways leading to establishment of senescence are proving to be more complex than was previously envisaged. Combining in-silico interactome analysis and functional target gene inhibition, stochastic modelling and live cell microscopy, we show here that there exists a dynamic feedback loop that is triggered by a DNA damage response (DDR) and, which after a delay of several days, locks the cell into an actively maintained state of 'deep' cellular senescence. The essential feature of the loop is that long-term activation of the checkpoint gene CDKN1A (p21) induces mitochondrial dysfunction and production of reactive oxygen species (ROS) through serial signalling through GADD45-MAPK14(p38MAPK)-GRB2-TGFBR2-TGFbeta. These ROS in turn replenish short-lived DNA damage foci and maintain an ongoing DDR. We show that this loop is both necessary and sufficient for the stability of growth arrest during the establishment of the senescent phenotype. This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2010 The BioModels.net Team.For more information see the terms of use.To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

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LARP7 ameliorates cellular senescence and aging-related atherosclerosis by allosterically enhancing SIRT1 deacetylase activity

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