Project description:Analysis of gene expression profile in Ras-induced senescent human diploid fibroblasts with or without depletion of fzr1/cdh1. Results provide insight into the effect on fzr1/cdh1 on the regulation of senescence-associated gene expression in human diploid fibroblasts.
Project description:Oncogenic ras activates several signaling pathways that cooperate in cell transformation. They include the ERK/MAP kinase pathway, the PI3K pathway and the Ral pathway among others. Surprisingly, in primary human fibroblasts, oncogenic ras expression induces senescence not transformation, but upon knockdown of ERK2 senescence is bypassed and transformation is stimulated. We used microarrays to characterize the gene expression programme of cells transformed by oncogenic ras, telomerase and knockdown of the ERK2 kinase. Primary human fibroblasts were co-infected with a retroviral vector that expresses oncogenic ras and either a control shRNA or an shRNA against ERK2. Cells with oncogenic ras and shRNA control entered senescence while cells with oncogenic ras and shRNA ERK2 bypassed senescence and underwent malignant transformation. Triplicates of these populations were used to purify total RNA, which we sent to Genome Quebec service for hybridization with Affymetrix microarrays.
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:Analysis of gene expression profile in Ras-induced senescent human diploid fibroblasts with or without depletion of fzr1/cdh1. Results provide insight into the effect on fzr1/cdh1 on the regulation of senescence-associated gene expression in human diploid fibroblasts. IMR-90-ER:Ras cells were cultured for 6 days with or without 4-hydroxytamoxifen (OHT) and were subsequently subjected to transfection with siRNA oligos against fzr1/cdh1 or control for three times (at 2 day intervals). Total RNA was isolated using Trizol reagent and were analyzed using the human 3D-Gene DNA chip (Toray) which that contains 25000 genes. The genome wide transcriptional response of proliferating cells (IMR si control2) and fzr1/cdh1 depleted senescent cells (IMR+OHT si cdh1) were compared to that of senescent cells (IMR+OHT si control).
Project description:Protein synthesis and autophagic degradation are regulated in an opposite manner by mammalian target of rapamycin (mTOR), whereas under certain conditions it would be beneficial if they occured in unison to handle rapid protein turnover. We observed a distinct cellular compartment at the trans-side of the Golgi apparatus, the ‘TOR-autophagy spatial coupling compartment’ (TASCC), where (auto)lysosomes and mTOR accumulated during Ras-induced senescence. mTOR recruitment to the TASCC was amino acid- and Rag guanosine triphosphatase (GTPase)-dependent, and disruption of mTOR localization to the TASCC suppressed interleukin-6/8 synthesis. TASCC-formation was observed during macrophage differentiation and in glomerular podocytes; both displayed increased protein secretion. The spatial coupling of cells’ catabolic and anabolic machinery could augment their respective functions and facilitate the mass synthesis of secretory proteins. To compare gene expression profile between growing and oncogenic Ras induced senescence, 4OHT inducible ER:H-RasV12 was stably expressed in IMR90 human diploid fibroblasts. Total RNA was isolated from day 0 and day 4 after 4OHT addition. There were 3 biological replicates for each of day0 and day 4 timepoints.
Project description:During oncogenic transformation, cells acquire genetic mutations that override the normal mechanisms regulating cellular proliferation. Excessive expression of activating transcription factor 4 (ATF4) is often observed in mammalian malignant tumors. However, little is known about the role of ATF4 in the malignant transformation of normal cells. Here, we show that ATF4 promotes oncogene-induced malignant transformation of murine fibroblasts by suppressing the expression of cellular senescence-associated genes. Ectopic expression of oncogenes, H-rasV12 and simian virus 40 large T-antigen, elicited malignant transformation of embryonic fibroblasts from wild-type mice, but not from Atf4-null (Atf4-/-) mice. The oncogenic stresses induced the expression of both Atf4 and cyclin-dependent kinase inhibitor 2a (Cdkn2a), in wild-type cells. Elevated levels of ATF4 successively suppressed the expression of cdkn2a encoding the cellular senescence-associated proteins, p16INK4a and p19ARF, thereby promoting oncogenic transformation. Conversely, the loss of ATF4 caused cellular senescence resulting from the consistent expression of p16INK4a and p19ARF. These findings reveal a novel function of ATF4: that of promoting oncogenic transformation by suppressing cellular senescence. Total 2 samples were derived from [1] H-Ras and SV40T expressing vector-transfected wild-type mouse embryonic fibroblasts (MEFs) and [2] H-Ras and SV40T expressing vector-transfected Atf4-/- MEFs
Project description:Oncogenic ras activates several signaling pathways that cooperate in cell transformation. They include the ERK/MAP kinase pathway, the PI3K pathway and the Ral pathway among others. Surprisingly, in primary human fibroblasts, oncogenic ras expression induces senescence not transformation, but upon knockdown of ERK2 senescence is bypassed and transformation is stimulated. We used microarrays to characterize the gene expression programme of cells transformed by oncogenic ras, telomerase and knockdown of the ERK2 kinase.
Project description:Analysis of gene expression changes following replicative senescnce Here we induced normal (primary) human diploid fibroblasts into senescence using serial passaging to determine which genes changed expression as a function of exit from the cell cycle.