Project description:We report the analysis of RNA sequencing aimed at understanding the effects induced by the knockdown of various target genes on senescent cells. These genes were initially identified through a genetic screening process designed to locate regulators responsible for upregulating SASP. Specifically, we focus on exploring the repercussions of SMARCA4 knockdown, a constituent of the SWI/SNF complex subunit, on the SASP and immune responses within senescent cells. The findings will help characterise the role of SMARCA4 inhibition on senescence surveillance by Natural Killer cells.
Project description:We report the analysis of RNA sequencing aimed at understanding the effects induced by the knockdown of SMARCA4 on the expression of repeat and transposable elements in senescent cells. SMARCA4 was initially identified as a target through a genetic screening process designed to locate regulators responsible for upregulating SASP. SMARCA4 is a constituent of the SWI/SNF complex subunit. The findings will help characterise he expression of repeat elements to elucidate the pathway by which SMARCA4 knockdown can promote cytokine expression and Natural Killer cell recruitment.
Project description:The expansion of repressive epigenetic marks has been implicated in heterochromatin formation during embryonic development, but the general applicability of this mechanism is unclear. Here we show that nuclear rearrangement of repressive histone marks H3K9me3 and H3K27me3 into non-overlapping structural layers characterizes senescence-associated heterochromatic foci (SAHF) formation in human fibroblasts. However, the global landscape of these repressive marks remains unchanged upon SAHF formation, suggesting that in somatic cells heterochromatin can be formed through the spatial repositioning of pre-existing repressively marked histones. This model is reinforced by the correlation of pre-senescent replication timing with both the subsequent layered structure of SAHFs and the global landscape of the repressive marks, allowing us to integrate microscopic and genomic information. Furthermore, modulation of SAHF structure does not affect the occupancy of these repressive marks nor vice versa. These experiments reveal that high-order heterochromatin formation and epigenetic remodeling of the genome can be discrete events. ChIP-seq for different histone marks in both growing and Ras-induced senescent fibroblasts, in the presence or absence of certain sh-RNAs K9me3Grow2.bed (growing) Chip Seq Analysis of H3K9me3 in ER:Ras expressing IMR90 human diploid fibroblasts d6 4OHT K9me3Sen2.bed (senescent) Chip Seq Analysis of H3K9me3 in ER:Ras expressing IMR90 human diploid fibroblasts with no treatment K9me2Grow3.bed (growing) Chip Seq Analysis of H3K9me2 in ER:Ras expressing IMR90 human diploid fibroblasts with no treatment K9me2Sen3.bed (senescent) Chip Seq Analysis of H3K9me2 in ER:Ras expressing IMR90 human diploid fibroblasts d6 4OHT K27me3Sen3.bed (senescent) Chip Seq Analysis of H3K27me3 in ER:Ras expressing IMR90 human diploid fibroblasts d6 4OHT K27me3Grow2.bed (growing) Chip Seq Analysis of H3K27me3 in ER:Ras expressing IMR90 human diploid fibroblasts with no treatment K36me3Grow2.bed (growing) Chip Seq Analysis of H3K36me3 in ER:Ras expressing IMR90 human diploid fibroblasts with no treatment K36me3Sen2.bed (senescent) Chip Seq Analysis of H3K36me3 in ER:Ras expressing IMR90 human diploid fibroblasts d6 4OHT K4me3Grow2.bed (growing) Chip Seq Analysis of H3K4me3 in ER:Ras expressing IMR90 human diploid fibroblasts with no treatment K4me3Sen3.bed (senescent) Chip Seq Analysis of H3K4me3 in ER:Ras expressing IMR90 human diploid fibroblasts d6 4OHT
Project description:The action of RB as a tumor suppressor has been difficult to define, in part, due to the redundancy of the related proteins p107 and p130. By coupling advanced RNAi technology to suppress RB, p107 or p130 with a genome wide analysis of gene expression in growing, quiescent or ras-senescent cells, we identified a unique and specific activity of RB in repressing DNA replication as cells exit the cell cycle into senescence, a tumor suppressive program. Experiment Overall Design: Expression profiles of IMR90 cells before and after RNAi-mediated supppression of RB, p107 or p130 in growing, quiescent or ras-induced senescent conditions. RNA was extracted from growing, low serum (0.1% FBS), confluent, or ras-senescent cells.
Project description:Total RNA was isolated from proliferating and senescent IMR90 cells to compare gene-expression to the changes in nucleolus-association in proliferating and senescent IMR90 cells.
Project description:We expressed either a wt or a phosphomutant version of ZFP36L1 in IMR90 ER:RAS cells. 7 days upon RAS induction (when the cells reach a fully senescent phenotype) we collected the RNA. ZFP36L1 is a RNA binding protein that binds to AU-rich elements in the 3âUTR of mRNAs and triggers their degradation. Our previous experiments showed that the activity of ZFP36L1 was key in the regulation of the senescent phenotype.By performing RNAseq we have uncovered the effect of expressing a constitutively active mutant of ZFP36L1 within the senescent transcriptome. 4 samples examined: Non-senescent cells (EV - 4OHT), Senescent cells (EV + 4OHT), Senescent cells expressing ZFP36L1wt and Senescent cells expressing ZFP36L1mut
Project description:Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently upregulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes. To understand the contribution of different genes, especially E2F7 to the expression profile of senescent cells, we infected human IMR90 cells with Ras and different hairpins. The infected population was selected using first with 2 ug/ml puromycin (Sigma) for 2 days, then 100 ug/ml hygromycin B (Roche) for 3 days. RNA was isolated 7 days after the puromycin selection and hybridized to Affymetrix microarrays. We tried to understand the effect of E2F7 in the transcription profile of senescent cells.
Project description:We expressed either a wt or a phosphomutant version of ZFP36L1 in IMR90 ER:RAS cells. 7 days upon RAS induction (when the cells reach a fully senescent phenotype) we collected the RNA. ZFP36L1 is a RNA binding protein that binds to AU-rich elements in the 3’UTR of mRNAs and triggers their degradation. Our previous experiments showed that the activity of ZFP36L1 was key in the regulation of the senescent phenotype.By performing RNAseq we have uncovered the effect of expressing a constitutively active mutant of ZFP36L1 within the senescent transcriptome.