Project description:The objective of the study was to investigate the effect of proteasome inhibition on glucocorticoid and estrogen receptor regulated gene expression. Experiment Overall Design: MCF-7 cells were treated with proteasome inhibitor (MG132), dexamethasone, 17b-estradiol or MG132 plus dexamethasone or MG132 plus 7b-estardiol. Control cells were not treated. RNA was collected from 2 biological experiments.
Project description:We report whole genome chromatin immunoprecipitation followed by sequencing (ChIP-seq) of histone 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 that MG132 treatment results in the spreading of the H3-trimethyl lysine 4 mark into gene bodies of a subset of induced genes in MCF-7 cells. The spreading of the H3K4me3 is concomitant with hyperacetylation (H3K27ac, K122ac and K9/14ac) of the corresponding gene TSS. H3 Lysine 36 trimethylation mark is enriched at genes that are induced by MG132. Finally, we show that proteasome inhibition establishes a chromatin state that enhances antiproliferative, while dampening cell proliferative gene expression programs relevant to breast cancer. The study provides a comprehensive resource of histone modifications in proteasome inhibited cells.
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.
Project description:The 26S proteasome regulates degradation of many cellular proteins to maintain cellular homeostasis. Disruption of proteasome activity followed by dysregulation of tumor suppressors and oncogenes is rampant in many cancers, hence chemical inhibitors of the proteasome have utility as cancer therapeutics, although the underlying mechanisms of their effects in the clinic is poorly understood. We have employed whole genome microarray expression profiling as a discovery platform to identify genes and potential signaling pathways that are affected MCF7 breast cancer cells are treated with MG132 a chemical inhibitor of the proteasome. Total RNA was collected from MCF7 breast cancer cells treated with DMSO (vehicle control) and 1 uM MG132 for 4 or 24H . We identified time dependent changes in the expression of genes enriched in p53 and estrogen receptor pathways, two signatures relevant to breast cancer biology.
Project description:Background: The combination of Proteasome inhibitor with Glucocorticoid is one of the most promising antileukemic treatments. Both agents act through pluripotent signal mediators. The two types of agents inhibit key signals that are considered crucial to their effects on malignant cells. Methodology/Principal Findings: Combined use of the two reagents on the lymphoblastic leukemia cell line CCRF-CEM has a range of effects on the viability that depend on the dose and the time used. Even though both reagents are capable of enhancing cell death on the CEM cell line, no combinatorial increase in cell death is detectable, until after the first 120 hours of treatment. In contrast, there are a number of combinatorial effects on the cell cycle phase distribution of treated cells, which indicates a potential for mutual signal disruption between glucocorticoid and proteasome inhibitor at multiple levels. Microarray analysis indicates that Prednisolone and MG132 elicit highly divergent, early-response molecular signatures on this cell line. We assayed levels of the antiapoptotic protein Mcl-1 as a potential model of late, downstream target regulation by both glucocorticoid and proteasome. Synchronized use of Prednisolone with MG132 results in temporary stabilization of Mcl-1 in CEM cells. Stabilization is not the result of a common mechanism of action on the genome, as Prednisolone and MG132 elicit nonreduntant molecular signatures, and it occurs also when the cells are treated at different timepoints with either agent. Conclusions/Significance: Our results show that this glucocorticoid-resistant ALL lymphoblast line is highly sensitive to proteasome inhibitor, and suggest that the proteasome inhibitor and the glucocorticoid regulate different direct target genes. This difference in immediate targets, when the two agents are applied in combination, may lead to negative or positive interference with mechanisms regulating viability of the leukemic lymphoblast. Signal interference between glucocorticoid Prednisolone and the proteasome inhibitor MG132 is expected to occur at more than one level, resulting in complex effects on intracellular signal transduction pathways. The net result depends on the development of individual downstream effects and interactions between key signal mediators. Elucidation of the conditions of interference between glucocorticoid and proteasome targets on leukemic cell fate is expected to improve effects of applied treatment combinations. Experimental setups consisted of the three following samples obtained after 4 h treatment: control, 10nM prednisolone, 1uM prednisolone, 10uM prednisolone, 100M-NM-<M prednisolone, 700M-NM-<M prednisolone, 200nM MG132, 2M-NM-<M MG132 and 20M-NM-<M MG132. Untreated cells were used as reference.
Project description:The 26S proteasome regulates general protein homeostasis and controls vital cellular processes, including cell division and transcriptional regulation. Cancer cells are dependent on the proper functioning of the proteasome to modulate gene expression networks that promote tumor growth. Proteasome inhibition has emerged as an effective therapeutic strategy, although mechanisms by which this approach achieves its outcomes remain unclear. We performed an integrative analysis of the transcriptome and chromatin landscape of MCF-7 breast cancer cells treated with a model proteasome inhibitor, MG132, to examine the consequences of proteasome inhibition on gene regulation. MG132 treatment initiated dynamic changes in chromatin accessibility at specific loci termed Differentially Open Chromatin Regions (DOCRs). DOCRs with increased accessibility were primarily distal to transcription start sites (TSS), while those with decreased accessibility were promoter proximal and distal to TSS. Promoter proximal DOCRs showed a unique chromatin architecture associated with distinct divergent transcription patterns. Conversely, DOCRs distal to TSS were enriched in oncogenic super enhancers that are predominantly accessible in non-basal compared to basal breast tumor subtypes. These data define distinct chromatin states and RNAPII transcription patterns, revealing molecular mechanisms by which the proteasome modulates the expression of gene networks intrinsic to breast cancer biology.
Project description:The 26S proteasome regulates general protein homeostasis and controls vital cellular processes, including cell division and transcriptional regulation. Cancer cells are dependent on the proper functioning of the proteasome to modulate gene expression networks that promote tumor growth. Proteasome inhibition has emerged as an effective therapeutic strategy, although mechanisms by which this approach achieves its outcomes remain unclear. We performed an integrative analysis of the transcriptome and chromatin landscape of MCF-7 breast cancer cells treated with a model proteasome inhibitor, MG132, to examine the consequences of proteasome inhibition on gene regulation. MG132 treatment initiated dynamic changes in chromatin accessibility at specific loci termed Differentially Open Chromatin Regions (DOCRs). DOCRs with increased accessibility were primarily distal to transcription start sites (TSS), while those with decreased accessibility were promoter proximal and distal to TSS. Promoter proximal DOCRs showed a unique chromatin architecture associated with distinct divergent transcription patterns. Conversely, DOCRs distal to TSS were enriched in oncogenic super enhancers that are predominantly accessible in non-basal compared to basal breast tumor subtypes. These data define distinct chromatin states and RNAPII transcription patterns, revealing molecular mechanisms by which the proteasome modulates the expression of gene networks intrinsic to breast cancer biology.