Transcriptional profiling by array after knockdown of ERK2 and ELK1 in human embryonic stem cells
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ABSTRACT: The ERK/MAPK signal transduction cascade is one of the key pathways regulating proliferation and differentiation in development and disease. In human embryonic stem cells (hESCs), ERK signaling is required for their self-renewing property. Here we studied the convergence of the ERK signaling cascade at the DNA by mapping genome-wide kinase-chromatin interactions for ERK2 in hESCs. We observe that ERK2 targets genes coding for small RNAs, histones, and genes involved in cellular metabolism and cell cycle. We find that the transcription factor ELK1 is essential in hESCs and that ERK2 co-occupies promoters bound by ELK1. Strikingly, promoters bound by ELK1 without ERK2 are occupied by Polycomb group proteins that repress genes involved in lineage commitment. In summary, we propose a model where extracellular signaling-stimulated proliferation and intrinsic repression of differentiation is integrated to maintain the identity of hESCs.
Project description:The ERK/MAPK signal transduction cascade is one of the key pathways regulating proliferation and differentiation in development and disease. In human embryonic stem cells (hESCs), ERK signaling is required for their self-renewing property. Here we studied the convergence of the ERK signaling cascade at the DNA by mapping genome-wide kinase-chromatin interactions for ERK2 in hESCs. We observe that ERK2 targets genes coding for small RNAs, histones, and genes involved in cellular metabolism and cell cycle. We find that the transcription factor ELK1 is essential in hESCs and that ERK2 co-occupies promoters bound by ELK1. Strikingly, promoters bound by ELK1 without ERK2 are occupied by Polycomb group proteins that repress genes involved in lineage commitment. In summary, we propose a model where extracellular signaling-stimulated proliferation and intrinsic repression of differentiation is integrated to maintain the identity of hESCs.
Project description:ELK1 is a well-known target of the ERK branch (EGF-responsive) of the MAP kinase pathway. This transcription profiling experiment studied the effects of ELK1 depletion by siRNA and subsequent EGF stimulation.
Project description:Using RNA-seq and canine MDCK epithelial cells, we analyzed mRNA expression profiles of cells overexpressing ERK2 and cells where the ERK pathway was activated for 24 hrs. For this purpose, three cell lines were used: parental MDCK cells, MDCK cells overexpressing FLAG-ERK2 or MDCK cells expressing conditionally active Raf protein (ΔRaf1:ER). Activation of the ERK pathways was achieved by the addition of 4-Hydroxytamoxifen that converts ΔRaf1:ER protein to the active form and it subsequently activates the ERK pathway.
Project description:The nuclear hormone receptor, estrogen receptor-alpha (ERα), and MAP kinases both play key roles in hormone-dependent cancers, yet their interplay and the integration of their signaling inputs remain poorly understood. In these studies, we document that estrogen-occupied ERα activates and interacts with ERK2, a downstream effector in the MAPK pathway, resulting in ERK2 and ERα colocalization at chromatin binding sites across the genome of breast cancer cells. KEYWORDS: siRNA knock-down, ligand treatment MCF-7 human breast adenocarcinoma cells were tranfected with control, ERK1 and ERK2 siRNA for 60 hours and treated with 0.1% EtOH (Vehicle) or 10 nM E2 for 4 hours or 24 hours, and cDNA microarray analyses were carried out using Affymetrix [HG-U133A_2] Affymetrix Human Genome U133A 2.0 Array.
Project description:The chromodomain helicase DNA binding protein CHD8 is among the most frequently found de-novo mutations in autism. Unlike other autism-risk genes, CHD8 mutations appear to be fully penetrant. Despite this prominent disease involvement, relatively little is known about its molecular function. Based on sequence homology, CHD8 is believed to be a chromatin regulator but mechanisms for its genomic targeting and its function on chromatin are unclear. Here, we developed a human cell model carrying conditional CHD8 loss-of-function alleles. Remarkably, while undifferentiated human embryonic stem (ES) cells required CHD8 for survival, postmitotic neurons survived following CHD8 depletion. Chromatin accessibility revealed that CHD8 is a highly potent and general chromatin activator, enhancing transcription of its direct target genes. We also found that CHD8 genomic binding in human neurons was significantly enriched at ELK1 DNA binding motifs as previously found in other cell types. Given its prominent role as effector molecule of the MAPK/ERK pathway, we decided to further explore its relationship with CHD8. ELK1 motif-containing CHD8 binding sites showed a higher degree of chromatin opening function of CHD8 than other CHD8 binding sites. Moreover, ELK1 was required for CHD8 binding to Elk1-containing sites, but not other sites. Finally, the anti-apoptotic function of CHD8 in human ES cells could be rescued by depletion of ELK1 and the enhancement of neurogenesis by ELK1 was dependent on presence of CHD8. In summary, our results establish a clear role of CHD8 for chromatin opening and transcriptional activation and a molecular and functional interdependence of CHD8 and ELK1. These data imply the involvement of the MAPK/ERK pathway effector ELK1 in the pathogenesis of autism caused by CHD8 mutations.
Project description:Activation of the extracellular signal regulated kinase-2 (ERK2) by phosphorylation has been shown to involve changes in protein dynamics, as determined by hydrogen-deuterium exchange mass spectrometry (HDX-MS) and NMR relaxation dispersion measurements. These can be described by a global exchange between two conformational states, named “L” and “R”, where R is associated with a catalytically productive ATP-binding mode. An ATP-competitive ERK1/2 inhibitor, Vertex-11e, has properties of conformation selection for the R-state, revealing movements of the activation loop that are allosterically coupled to the kinase active site. However, the features of inhibitors important for R-state selection are unknown. Here we survey a panel of ATP-competitive ERK inhibitors using HDX-MS and NMR and identify 14 new molecules with properties of R-state selection. They reveal effects propagated to distal regions in the P+1 and helix αF segments surrounding the activation loop, as well as helix αL16. Crystal structures of inhibitor complexes with ERK2 reveal systematic shifts in the Gly loop and helix αC, mediated by a Tyr-Tyr ring stacking interaction and the conserved Lys-Glu salt bridge. The findings suggest a model for the R-state involving small movements in the N-lobe that promote compactness within the kinase active site and alter mobility surrounding the activation loop. Such properties of conformation selection might be exploited to modulate the protein docking interface used by ERK substrates and effectors.
Project description:Alpha lipoic acid is reported to inhibit neutrophil lineage determination by targeting transcription factor ELK1 in granulocyte-monocyte progenitors. Here, we provide new evidence of alpha lipoic acid in promoting erythroid differentiation by targeting transcription factor ELK1 in CD34+CD371– hematopoietic stem progenitor cells. Over expression of both L-ELK1 and S-ELK1 greatly inhibit erythroid cell differentiation, but not knocking down of ELK1. Thus, RNAseq of CD34+CD123+CD38+CD371– HSPCs is performed to dissect the molecular mechanism of ELK1 in blocking erythrocyte differentiation.