Project description:Environmental stresses that disrupt protein homeostasis induce phosphorylation of eIF2, triggering repression of global protein synthesis coincident with preferential translation of ATF4, a transcriptional activator of the Integrated stress response (ISR). Depending on the extent of protein disruption, ATF4 may not be able to restore proteostatic control and instead switch to a terminal outcome that features elevated expression of the transcription factor CHOP (GADD153/DDIT3). The focus of this study was to define the mechanisms by which CHOP directs gene regulatory networks that determine cell fate. We find that in response to proteasome inhibition, CHOP induces the expression of a collection of genes encoding transcription regulators, including ATF5, which is preferentially translated during eIF2 phosphorylation. Transcriptional expression of ATF5 is directly activated by both CHOP and ATF4. Knock-down of ATF5 increased cell survival in response to proteasome inhibition, supporting the idea that both ATF5 and CHOP have pro-apoptotic functions. Transcriptome analyses of ATF5-dependent genes revealed targets involved in apoptosis, including, NOXA, which is important for inducing cell death during proteasome inhibition. This study suggests that the ISR features a feed-forward loop of stress induced transcriptional regulators, each subject to transcriptional and translational control that can switch cell fate towards apoptosis. 8 plates (10cm) of WT and and 8 plates (10cm) of CHOP-/- MEF cells were subject to no stress (4 each for a total of 8) or treated for 8 hours with 1uM MG132 (4 each for a total of 8). Unstressed cells were harvested at the same time as the stressed cells
Project description:Environmental stresses that disrupt protein homeostasis induce phosphorylation of eIF2, triggering repression of global protein synthesis coincident with preferential translation of ATF4, a transcriptional activator of the Integrated stress response (ISR). Depending on the extent of protein disruption, ATF4 may not be able to restore proteostatic control and instead switch to a terminal outcome that features elevated expression of the transcription factor CHOP (GADD153/DDIT3). The focus of this study was to define the mechanisms by which CHOP directs gene regulatory networks that determine cell fate. We find that in response to proteasome inhibition, CHOP induces the expression of a collection of genes encoding transcription regulators, including ATF5, which is preferentially translated during eIF2 phosphorylation. Transcriptional expression of ATF5 is directly activated by both CHOP and ATF4. Knock-down of ATF5 increased cell survival in response to proteasome inhibition, supporting the idea that both ATF5 and CHOP have pro-apoptotic functions. Transcriptome analyses of ATF5-dependent genes revealed targets involved in apoptosis, including, NOXA, which is important for inducing cell death during proteasome inhibition. This study suggests that the ISR features a feed-forward loop of stress induced transcriptional regulators, each subject to transcriptional and translational control that can switch cell fate towards apoptosis. 8 plates (10cm) of WT and and 8 plates (10cm) of ATF5-KD MEF cells were subject to no stress (4 each for a total of 8) or treated for 8 hours with 1uM MG132 (4 each for a total of 8). Unstressed cells were harvested at the same time as the stressed cells
Project description:Environmental stresses that disrupt protein homeostasis induce phosphorylation of eIF2, triggering repression of global protein synthesis coincident with preferential translation of ATF4, a transcriptional activator of the Integrated stress response (ISR). Depending on the extent of protein disruption, ATF4 may not be able to restore proteostatic control and instead switch to a terminal outcome that features elevated expression of the transcription factor CHOP (GADD153/DDIT3). The focus of this study was to define the mechanisms by which CHOP directs gene regulatory networks that determine cell fate. We find that in response to proteasome inhibition, CHOP induces the expression of a collection of genes encoding transcription regulators, including ATF5, which is preferentially translated during eIF2 phosphorylation. Transcriptional expression of ATF5 is directly activated by both CHOP and ATF4. Knock-down of ATF5 increased cell survival in response to proteasome inhibition, supporting the idea that both ATF5 and CHOP have pro-apoptotic functions. Transcriptome analyses of ATF5-dependent genes revealed targets involved in apoptosis, including, NOXA, which is important for inducing cell death during proteasome inhibition. This study suggests that the ISR features a feed-forward loop of stress induced transcriptional regulators, each subject to transcriptional and translational control that can switch cell fate towards apoptosis.
Project description:Environmental stresses that disrupt protein homeostasis induce phosphorylation of eIF2, triggering repression of global protein synthesis coincident with preferential translation of ATF4, a transcriptional activator of the Integrated stress response (ISR). Depending on the extent of protein disruption, ATF4 may not be able to restore proteostatic control and instead switch to a terminal outcome that features elevated expression of the transcription factor CHOP (GADD153/DDIT3). The focus of this study was to define the mechanisms by which CHOP directs gene regulatory networks that determine cell fate. We find that in response to proteasome inhibition, CHOP induces the expression of a collection of genes encoding transcription regulators, including ATF5, which is preferentially translated during eIF2 phosphorylation. Transcriptional expression of ATF5 is directly activated by both CHOP and ATF4. Knock-down of ATF5 increased cell survival in response to proteasome inhibition, supporting the idea that both ATF5 and CHOP have pro-apoptotic functions. Transcriptome analyses of ATF5-dependent genes revealed targets involved in apoptosis, including, NOXA, which is important for inducing cell death during proteasome inhibition. This study suggests that the ISR features a feed-forward loop of stress induced transcriptional regulators, each subject to transcriptional and translational control that can switch cell fate towards apoptosis.
Project description:We report whole genome chromatin immunoprecipitation followed by sequencing (ChIP-seq) of 3 different RNA Pol II CTD modifications in MCF-7 breast cancer cells treated with vehicle (UNTR) or the proteasome inhibitor MG132 for 4 (MG4H) or 24 (MG24H) hours. We find the non-phosphorylated form of RNA Pol II CTD accumulates at TSS of all expressed genes in proteasome inhibited cells, particularly after 24H of MG132 treatment. Proteasome inhibition enhances Ser5-P and Ser2-P binding at TSS of genes induced by MG132. We note that proteasome inhibition establishes unique Ser2-P 5’ to 3’ gene profiles at induced compared to repressed genes. Overall proteasome inhibition enhances RNA Pol II processivity and expression of gene networks relevant to breast cancer. The study provides a comprehensive resource of RNA Pol II binding in proteasome inhibited cells.