Project description:Senescent cells are a major cause of organismal aging and a key target for anti-aging therapies. Persistent DNA damage signaling is a primary driver of the induction and maintenance of cellular senescence. However, many DNA damaging stimuli that induce senescence, such as irradiation or transient exposure to genotoxic drugs, are transient. The mechanisms underlying persistent damage signaling in senescent cells, and why senescent cells fail to repair damaged DNA, remain unknown. Here, we were able to assess the mechanisms underlying persistence of DNA damage and senescence maintenance by designing a precisely controllable senescence system that does not require potent stressors to induce senescence. We demonstrate that sustained mTORC1 signaling in senescent cells causes gradually accumulating DNA damage and an inflammatory response that maintains cell-cycle arrest. Markedly, activation of E2F transcription, which promotes expression of DNA repair proteins, can reverse accumulated DNA damage. Thus, persistent DNA damage signaling arises in senescent cells by uncoupling of mTORC1 and E2F signaling, whereby prolonged mTORC1 activity causes gradually increasing DNA damage that cannot be sufficiently repaired without induction of protective E2F target genes.
Project description:To identify differentially expressed genes during cellular senescence, we performed transcriptional profiling with RNA sequencing (RNA-seq) before and after senescence induction using a stress-induced senescence model (bleomycin-induced senescence).
Project description:We report the application of an improved assay for transposase-accessible chromatin with high-throughput sequencing in profiling changes of chromatin openning state in senescent human stromal cells. By obtaining over four billion bases of sequence from Tn5 transposase-processed chromosome DNAs, we generated genome-wide chromatin-state maps of human primary stromal cells (with a starting cell number of 50,000). This study provides a framework for the application of ATAC-Seq technique towards spatiotemporal chromatin configuration of human stromal cells upon DNA damage-induced senescence.
Project description:The senescence of mammalian cells is characterized by a proliferative arrest in response to stress and the expression of an inflammatory phenotype. We discovered that H2A.J, a poorly studied H2A variant found only in mammals, accumulates in human fibroblasts in senescence with persistent DNA damage. Knock-down of H2A.J interfered with the derepression of a set of inflammatory genes that contribute to the senescent-associated secretory phenotype (SASP), and over-expression of H2A.J increased the expression of some of these genes in proliferating cells. H2A.J accumulation may thus promote the signaling of senescent cells to the immune system. 41 samples analysed
Project description:The goals of this study is to analyse transcriptionnal changes in senescent cells and to compare them with ChIPseq data for several histones marks and proteins of the SUMO machinery mRNA profiling of proliferative versus Ras-induced senescent humain primary fibroblasts 5 days post-infection