Expression data from WT, E2f8 KO, Rb KO and Rb;E2f8 DKO spleen Ter19+CD71high sorted cells
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE52157 | GEO | 2014/05/30
SECONDARY ACCESSION(S): PRJNA227047
REPOSITORIES: GEO
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Project description:To understand molecular mechanisms underlying the synergy of Rb loss and E2F8 loss, we used gene expression profiling to assess molecular changes in Mx1-Cre-mediated knockout (KO) mice using RNA isolated from sorted Ter119+CD71high Erythroblasts. The top four upregulated and enriched pathways in the DKO mice included DNA replication, DNA damage response, DNA repair, and RNA processing. Interestingly, the majority of upregulated genes in the enriched sections of the four shared pathways contain E2f binding site(s) in their promoters, suggesting that Rb and E2F8 largely repress those genes through the E2f binding sites. Collectively, our data suggest that Rb and E2F8 co-regulate E2F-responsive genes. Spleen Ter119+CD71high cells were sorted from WT, E2f8 KO, Rb KO and E2f8;Rb DKO mice
2014-05-30 | E-GEOD-52157 | biostudies-arrayexpress
Project description:Mutations in cancer are due in part to DNA cytosine deamination by APOBEC3B (A3B). While low in healthy tissues, A3B expression and activity are elevated in tumors and further increase in metastases. However, molecular mechanisms responsible for A3B transcriptional regulation are poorly understood. Here, we address whether the RB/E2F pathway, which is often dysregulated in breast cancer, is a molecular trigger of A3B overexpression. First, an A3B promoter-driven luciferase reporter was used to demonstrate reporter activation by disruption of only one out of five predicted E2F binding sites. Second, A3B-luciferase reporter activation was also triggered by expressing the BK polyomavirus T-antigen, which inactivates RB and thereby alleviates repression of E2F regulated genes. Importantly, A3B-luciferase reporter induction by BK polyomavirus T-antigen could not be further increased by mutating the functional E2F binding site. Third, both CRISPR disruption and targeted base substitutions in the endogenous E2F binding site caused strong A3B upregulation and confirmed importance of this regulatory element. Fourth, proteomics experiments showed that members of the DREAM and PRC1.6-complexes including multiple E2F family members are able to bind to wild-type but not E2F mutant promoter sequences. Finally, a combination of genetic and biochemical studies implicated E2F4 and E2F6 in endogenous A3B gene repression. Altogether, our studies demonstrate that A3B expression is suppressed in normal cells by the RB/E2F axis and that viral or mutational disruption of this pathway causes overexpression of this DNA deaminase in cancer and contributes mutational fuel to tumor evolution.
2020-10-19 | PXD020473 | Pride
Project description:E2F transcription factors are central regulators of cell cycle progression and cell fate decisions in mammalian cells. E2F4 is a transcriptional repressor implicated in cell cycle arrest and whose repressive activity depends on its interaction with members of the RB family. E2F4 often represents the predominant E2F activity in cells. Here we show that E2F4 is important for the proliferation and the survival of mouse embryonic stem cells. In these cells, E2F4 acts in part as a transcriptional activator that promotes the expression of cell cycle genes. Importantly, this role for E2F4 is completely independent of the RB family. Accordingly, an unbiased analysis of the E2F4 interactome shows that E2F4 functionally interacts with chromatin regulators associated with gene activation in RB family-mutant cells. Taken together, our findings uncover a non-canonical role for E2F4 that reveal novel insights into the biology of rapidly dividing cell types.
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Project description:RB’s interaction with chromatin is key to understanding its molecular functions. Using a novel ChIP-sequencing protocol, we identify the precise chromatin loci bound by various forms of human RB. RB targets three fundamentally different types of loci (promoters, enhancers, CTCF-sites), that are largely distinguishable by the mutually exclusive presence of E2F1, c-JUN and CTCF. E2F/DP facilitates RB association with promoters, whereas AP-1 recruits RB to enhancers. RB’s association with promoters and enhancers fluctuates: G1-arrest enriched RB at promoters, while S-phase progression redistributed RB towards enhancers. RB binding to RB/CTCF sites was unaltered by cell cycle progression. RB-bound promoters include the classic E2F targets and are similar between cell types. However, RB-bound enhancers are associated with different gene categories, including, notably, MAPK signaling, and they vary between cell types. We propose that RB has a well-preserved role controlling E2F in G1, and cell type-specific effects at enhancers when cells enter S-phase.
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Project description:Hyper-phosphorylation of RB controls its interaction with E2F and inhibits its tumor suppressor properties. However, during G1 active RB can be mono-phosphorylated on any one of 14 CDK phosphorylation sites. Here we used quantitative proteomics to profile protein complexes formed by each mono-phosphorylated RB isoform (mP-RB) and identified the associated transcriptional outputs. The results show that the 14 sites of mono-phosphorylation co-ordinate RB’s interactions and confer functional specificity. All 14 mP-RBs interact with E2F/DP proteins but they provide different shades of E2F regulation. RB mono-phosphorylation at S811, for example, alters RB transcriptional activity by promoting its association with NuRD complexes. The greatest functional differences between mP-RBs are evident beyond the cell cycle machinery. RB mono-phosphorylation at S811 or T826 stimulates the expression of oxidative phosphorylation genes, increasing cellular oxygen consumption. These results indicate that RB activation signals are integrated in a phosphorylation code that determines the diversity of RB activity.
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Project description:The Rb/E2F tumor suppressor regulates gene expression to control the onset and timing of differentiation in many different cell types during development. This critical function makes Rb/E2F a frequent target for inactivation in tumors of diverse tissue origin. However, the mechanisms by which Rb/E2F governs tissue-specific gene regulation in vivo are poorly understood. We have determined the genome-wide binding profiles for components of the C. elegans Rb/E2F transcriptional regulatory pathway in the germ line, the intestine, and broadly in somatic tissues. Rb/E2F exhibits highly tissue-specific regulation, with unique sets of target genes that are activated or repressed depending on whether cells are in a progenitor (germ line) or terminally differentiated (somatic) state. In particular, LIN-35 binding is impaired in the germ line relative to the soma. Moreover, in the intestine, LIN-35 binds independently of EFL-1/DPL-1 at broad intergenic sites at which the heterochromatin protein HPL-2 also binds. Finally, recently defined âHOTâ sites, which are non-specifically bound by many unrelated factors, appear to be restricted primarily to somatic tissues, suggesting that germ line chromatin is in a state that globally restricts promiscuous association of regulatory factors. In sum, these tissue-specific binding profiles led to significant mechanistic insights into tissue-specific properties of Rb/E2F function in C. elegans that are likely relevant to other organisms.
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2008-06-14 | E-GEOD-6206 | biostudies-arrayexpress
Project description:This serie was performed on liver progenitor isolated based on their expression of the Sca1 surface marker. It contains two independent samples from Rb family deficient liver and three independent samples from control liver, all isolated 2 weeks after Tamoxifen-induced Rb family ablation. Hematopoietic (CD45, Ter119) and endothelial (CD31) markers were used as negative selection markers to exclude blood or endothelial cells from the isolated fraction.
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Project description:Most E2F-binding sites repress transcription through the recruitment of Retinoblasoma (RB) family members until the end of the G1 cell-cycle phase. Although the MYB promoter contains an E2F-binding site, its transcription is activated shortly after the exit from quiescence, before RB family members inactivation, by unknown mechanisms. We had previously uncovered a nuclear factor distinct from E2F, Myb-sp, whose DNA-binding site overlapped the E2F element and had hypothesized that this factor might overcome the transcriptional repression of MYB by E2F-RB family members. We have purified Myb-sp and discovered that Myc-associated zinc finger proteins (MAZ) are major components. We show that various MAZ isoforms are present in Myb-sp and activate transcription via the MYB-E2F element. Moreover, while forced RB or p130 expression repressed the activity of a luciferase reporter driven by the MYB-E2F element, co-expression of MAZ proteins not only reverted repression, but also activated transcription. Finally, we show that MAZ binds the MYB promoter in vivo, that its binding site is critical for MYB transactivation, and that MAZ knockdown inhibits MYB expression during the exit from quiescence. Together, these data indicate that MAZ is essential to bypass MYB promoter repression by RB family members and to induce MYB expression.
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