The Varied Roles of Notch in Cancer Aster, Jon C; Pear, Warren S; Blacklow, Stephen C
Annual review of pathology,
01/2017, Letnik:
12, Številka:
1
Journal Article
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Notch receptors influence cellular behavior by participating in a seemingly simple signaling pathway, but outcomes produced by Notch signaling are remarkably varied depending on signal dose and cell ...context. Here, after briefly reviewing new insights into physiologic mechanisms of Notch signaling in healthy tissues and defects in Notch signaling that contribute to congenital disorders and viral infection, we discuss the varied roles of Notch in cancer, focusing on cell autonomous activities that may be either oncogenic or tumor suppressive.
During wound healing in adult mouse skin, hair follicles and then adipocytes regenerate. Adipocytes regenerate from myofibroblasts, a specialized contractile wound fibroblast. Here we study wound ...fibroblast diversity using single-cell RNA-sequencing. On analysis, wound fibroblasts group into twelve clusters. Pseudotime and RNA velocity analyses reveal that some clusters likely represent consecutive differentiation states toward a contractile phenotype, while others appear to represent distinct fibroblast lineages. One subset of fibroblasts expresses hematopoietic markers, suggesting their myeloid origin. We validate this finding using single-cell western blot and single-cell RNA-sequencing on genetically labeled myofibroblasts. Using bone marrow transplantation and Cre recombinase-based lineage tracing experiments, we rule out cell fusion events and confirm that hematopoietic lineage cells give rise to a subset of myofibroblasts and rare regenerated adipocytes. In conclusion, our study reveals that wounding induces a high degree of heterogeneity among fibroblasts and recruits highly plastic myeloid cells that contribute to adipocyte regeneration.
Group 2 innate lymphoid cells (ILC2) are innate lymphocytes that confer protective type 2 immunity during helminth infection and are also involved in allergic airway inflammation. Here we report that ...ILC2 development required T cell factor 1 (TCF-1, the product of the Tcf7 gene), a transcription factor also implicated in T cell lineage specification. Tcf7−/− mice lack ILC2, and were unable to mount ILC2-mediated innate type 2 immune responses. Forced expression of TCF-1 in bone marrow progenitors partially bypassed the requirement for Notch signaling in the generation of ILC2 in vivo. TCF-1 acted through both GATA-3-dependent and GATA-3-independent pathways to promote the generation of ILC2. These results are reminiscent of the critical roles of TCF-1 in early T cell development. Hence, transcription factors that underlie early steps of T cell development are also implicated in the development of innate lymphoid cells.
► TCF-1 is required for the generation of ILC2 ► ILC2-mediated immune responses are compromised in Tcf7−/− mice ► TCF-1 promotes ILC2 development under Notch signaling ► TCF-1 acts through both GATA-3-dependent and GATA-3-independent mechanisms
COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of COP1 resides within a ...WD40-repeat domain that also binds to Trib proteins, which are adaptors for C/EBPα degradation. Here we report structures of the human COP1 WD40 domain in isolation, and complexes of the human and Arabidopsis thaliana COP1 WD40 domains with the binding motif of Trib1. The human and Arabidopsis WD40 domains are seven-bladed β propellers with an inserted loop on the bottom face of the first blade. The Trib1 peptide binds in an extended conformation to a highly conserved surface on the top face of the β propeller, indicating a general mode for recognition of peptide motifs by COP1. Together, these studies identify the structural basis and key interactions for motif recognition by COP1, and hint at how Trib1 autoinhibition is overcome to target C/EBPα for degradation.
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•X-Ray structures reported for human and plant COP1 β-propeller-peptide complexes•Trib1 peptides bind to a conserved surface on the top face of the propeller•Structures reveal a universal mechanism for motif recognition by COP1•Competition binding assays confirm importance of consensus VP sequence
COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of COP1 resides within a WD40-repeat domain that also binds to Trib proteins, the adaptors for C/EBPα degradation. Uljon et al. identify the structural basis and key interactions for motif recognition by COP1, and hint at how Trib1 autoinhibition is overcome to target C/EBPα for degradation.
Two models are proposed to explain Notch function during helper T (Th) cell differentiation. One argues that Notch instructs one Th cell fate over the other, whereas the other posits that Notch ...function is dictated by cytokines. Here we provide a detailed mechanistic study investigating the role of Notch in orchestrating Th cell differentiation. Notch neither instructed Th cell differentiation nor did cytokines direct Notch activity, but instead, Notch simultaneously regulated the Th1, Th2, and Th17 cell genetic programs independently of cytokine signals. In addition to regulating these programs in both polarized and nonpolarized Th cells, we identified Ifng as a direct Notch target. Notch bound the Ifng CNS-22 enhancer, where it synergized with Tbet at the promoter. Thus, Notch acts as an unbiased amplifier of Th cell differentiation. Our data provide a paradigm for Notch in hematopoiesis, with Notch simultaneously orchestrating multiple lineage programs, rather than restricting alternate outcomes.
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•Notch concurrently regulates Th1, Th2, and Th17 cell differentiation•Notch activity is unbiased and is not affected by the cytokine environment•Notch regulates Ifng at the Ifng CNS-22 and synergizes with Tbet at the promoter•Notch can simultaneously orchestrate multiple lineage programs
The main oncogenic driver in T-lymphoblastic leukemia is NOTCH1, which activates genes by forming chromatin-associated Notch transcription complexes. Gamma-secretase-inhibitor treatment prevents ...NOTCH1 nuclear localization, but most genes with NOTCH1-binding sites are insensitive to gamma-secretase inhibitors. Here, we demonstrate that fewer than 10% of NOTCH1-binding sites show dynamic changes in NOTCH1 occupancy when T-lymphoblastic leukemia cells are toggled between the Notch-on and -off states with gamma-secretase inhibiters. Dynamic NOTCH1 sites are functional, being highly associated with Notch target genes, are located mainly in distal enhancers, and frequently overlap with RUNX1 binding. In line with the latter association, we show that expression of IL7R , a gene with key roles in normal T-cell development and in T-lymphoblastic leukemia, is coordinately regulated by Runx factors and dynamic NOTCH1 binding to distal enhancers. Like IL7R , most Notch target genes and associated dynamic NOTCH1-binding sites cooccupy chromatin domains defined by constitutive binding of CCCTC binding factor, which appears to restrict the regulatory potential of dynamic NOTCH1 sites. More remarkably, the majority of dynamic NOTCH1 sites lie in superenhancers, distal elements with exceptionally broad and high levels of H3K27ac. Changes in Notch occupancy produces dynamic alterations in H3K27ac levels across the entire breadth of superenhancers and in the promoters of Notch target genes. These findings link regulation of superenhancer function to NOTCH1, a master regulatory factor and potent oncoprotein in the context of immature T cells, and delineate a generally applicable roadmap for identifying functional Notch sites in cellular genomes.
Although it is well recognized that haematopoietic stem cells (HSCs) develop from a specialized population of endothelial cells known as haemogenic endothelium, the regulatory pathways that control ...this transition are not well defined. Here we identify Sox17 as a key regulator of haemogenic endothelial development. Analysis of Sox17-GFP reporter mice revealed that Sox17 is expressed in haemogenic endothelium and emerging HSCs and that it is required for HSC development. Using the mouse embryonic stem cell differentiation model, we show that Sox17 is also expressed in haemogenic endothelium generated in vitro and that it plays a pivotal role in the development and/or expansion of haemogenic endothelium through the Notch signalling pathway. Taken together, these findings position Sox17 as a key regulator of haemogenic endothelial and haematopoietic development.
Notch1 is a rational therapeutic target in several human cancers, but as a transcriptional regulator, it poses a drug discovery challenge. To identify Notch1 modulators, we performed two cell-based, ...high-throughput screens for small-molecule inhibitors and cDNA enhancers of a NOTCH1 allele bearing a leukemia-associated mutation. Sarco/endoplasmic reticulum calcium ATPase (SERCA) channels emerged at the intersection of these complementary screens. SERCA inhibition preferentially impairs the maturation and activity of mutated Notch1 receptors and induces a G0/G1 arrest in NOTCH1-mutated human leukemia cells. A small-molecule SERCA inhibitor has on-target activity in two mouse models of human leukemia and interferes with Notch signaling in Drosophila. These studies “credential” SERCA as a therapeutic target in cancers associated with NOTCH1 mutations.
► Intersecting high-throughput screens identify SERCA inhibition to modulate Notch1 ► A small-molecule SERCA inhibitor has on-target antileukemia activity in vitro ► A SERCA inhibitor has on-target antileukemia activity in T-ALL mouse models ► SERCA inhibition preferentially impairs the maturation of mutated Notch1 receptors
Notch1 regulates gene expression by associating with the DNA-binding factor RBPJ and is oncogenic in murine and human T-cell progenitors. Using ChIP-Seq, we find that in human and murine ...T-lymphoblastic leukemia (TLL) genomes Notch1 binds preferentially to promoters, to RBPJ binding sites, and near imputed ZNF143, ETS, and RUNX sites. ChIP-Seq confirmed that ZNF143 binds to ∼40% of Notch1 sites. Notch1/ZNF143 sites are characterized by high Notch1 and ZNF143 signals, frequent cobinding of RBPJ (generally through sites embedded within ZNF143 motifs), strong promoter bias, and relatively low mean levels of activating chromatin marks. RBPJ and ZNF143 binding to DNA is mutually exclusive in vitro, suggesting RBPJ/Notch1 and ZNF143 complexes exchange on these sites in cells. K-means clustering of Notch1 binding sites and associated motifs identified conserved Notch1-RUNX, Notch1-ETS, Notch1-RBPJ, Notch1-ZNF143, and Notch1-ZNF143-ETS clusters with different genomic distributions and levels of chromatin marks. Although Notch1 binds mainly to gene promoters, ∼75% of direct target genes lack promoter binding and are presumably regulated by enhancers, which were identified near MYC, DTX1, IGF1R, IL7R, and the GIMAP cluster. Human and murine TLL genomes also have many sites that bind only RBPJ. Murine RBPJ-only sites are highly enriched for imputed REST (a DNA-binding transcriptional repressor) sites, whereas human RPBJ-only sites lack REST motifs and are more highly enriched for imputed CREB sites. Thus, there is a conserved network of cis-regulatory factors that interacts with Notch1 to regulate gene expression in TLL cells, as well as unique classes of divergent RBPJ-only sites that also likely regulate transcription.
Notch signaling in leukemia Aster, Jon C; Pear, Warren S; Blacklow, Stephen C
Annual review of pathology,
01/2008, Letnik:
3
Journal Article
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Recent discoveries indicate that gain-of-function mutations in the Notch1 receptor are very common in human T cell acute lymphoblastic leukemia/lymphoma. This review discusses what these mutations ...have taught us about normal and pathophysiologic Notch1 signaling, and how these insights may lead to new targeted therapies for patients with this aggressive form of cancer.
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