| 61. |
- Cova, Giovanni, et al.
(författare)
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Helios represses megakaryocyte priming in hematopoietic stem and progenitor cells
- 2021
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 218:10
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of cell fate decisions in hematopoietic stem cells is incomplete. Here, we show that the transcription factor Helios is highly expressed in murine hematopoietic stem and progenitor cells (HSPCs), where it is required to suppress the separation of the platelet/megakaryocyte lineage from the HSPC pool. Helios acts mainly in quiescent cells, where it directly represses the megakaryocyte gene expression program in cells as early as the stem cell stage. Helios binding promotes chromatin compaction, notably at the regulatory regions of platelet-specific genes recognized by the Gata2 and Runx1 transcriptional activators, implicated in megakaryocyte priming. Helios null HSPCs are biased toward the megakaryocyte lineage at the expense of the lymphoid and partially resemble cells of aging animals. We propose that Helios acts as a guardian of HSPC pluripotency by continuously repressing the megakaryocyte fate, which in turn allows downstream lymphoid priming to take place. These results highlight the importance of negative and positive priming events in lineage commitment.
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| 62. |
- Cunha, Sara I, et al.
(författare)
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Genetic and pharmacological targeting of activin receptor-like kinase 1 impairs tumor growth and angiogenesis
- 2010
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Ingår i: Journal of Experimental Medicine. - : The Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 207:1, s. 85-100
-
Tidskriftsartikel (refereegranskat)abstract
- Members of the transforming growth factor beta (TGF-beta) family have been genetically linked to vascular formation during embryogenesis. However, contradictory studies about the role of TGF-beta and other family members with reported vascular functions, such as bone morphogenetic protein (BMP) 9, in physiological and pathological angiogenesis make the need for mechanistic studies apparent. We demonstrate, by genetic and pharmacological means, that the TGF-beta and BMP9 receptor activin receptor-like kinase (ALK) 1 represents a new therapeutic target for tumor angiogenesis. Diminution of ALK1 gene dosage or systemic treatment with the ALK1-F(c) fusion protein RAP-041 retarded tumor growth and progression by inhibition of angiogenesis in a transgenic mouse model of multistep tumorigenesis. Furthermore, RAP-041 significantly impaired the in vitro and in vivo angiogenic response toward vascular endothelial growth factor A and basic fibroblast growth factor. In seeking the mechanism for the observed effects, we uncovered an unexpected signaling synergy between TGF-beta and BMP9, through which the combined action of the two factors augmented the endothelial cell response to angiogenic stimuli. We delineate a decisive role for signaling by TGF-beta family members in tumor angiogenesis and offer mechanistic insight for the forthcoming clinical development of drugs blocking ALK1 in oncology.
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| 63. |
- de Miranda, Noel F. C. C., et al.
(författare)
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DNA repair genes are selectively mutated in diffuse large B cell lymphomas
- 2013
-
Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 210:9, s. 1729-1742
-
Tidskriftsartikel (refereegranskat)abstract
- DNA repair mechanisms are fundamental for B cell development, which relies on the somatic diversification of the immunoglobulin genes by V(D)J recombination, somatic hypermutation, and class switch recombination. Their failure is postulated to promote genomic instability and malignant transformation in B cells. By performing targeted sequencing of 73 key DNA repair genes in 29 B cell lymphoma samples, somatic and germline mutations were identified in various DNA repair pathways, mainly in diffuse large B cell lymphomas (DLBCLs). Mutations in mismatch repair genes (EXO1, MSH2, and MSH6) were associated with microsatellite instability, increased number of somatic insertions/deletions, and altered mutation signatures in tumors. Somatic mutations in nonhomologous end-joining (NHEJ) genes (DCLRE1C/ARTEMIS, PRKDC/DNA-PKcs, XRCC5/KU80, and XRCC6/KU70) were identified in four DLBCL tumors and cytogenetic analyses revealed that translocations involving the immunoglobulin-heavy chain locus occurred exclusively in NHEJ-mutated samples. The novel mutation targets, CHEK2 and PARP1, were further screened in expanded DLBCL cohorts, and somatic as well as novel and rare germline mutations were identified in 8 and 5% of analyzed tumors, respectively. By correlating defects in a subset of DNA damage response and repair genes with genomic instability events in tumors, we propose that these genes play a role in DLBCL lymphomagenesis.
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| 64. |
- deCamposLima, PO, et al.
(författare)
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Epitope-dependent selection of highly restricted or diverse T cell receptor repertoires in response to persistent infection by Epstein-Barr virus
- 1997
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Ingår i: The Journal of experimental medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 186:1, s. 83-89
-
Tidskriftsartikel (refereegranskat)abstract
- The T cell receptor (TCR) repertoires of cytotoxic responses to the immunodominant and subdominant HLA A11–restricted epitopes in the Epstein-Barr virus (EBV) nuclear antigen-4 were investigated in four healthy virus carriers. The response to the subdominant epitope (EBNA4 399-408, designated AVF) was highly restricted with conserved Vβ usage and identical length and amino acid motifs in the third complementarity-determining regions (CDR3), while a broad repertoire using different combinations of TCR-α/β V and J segments and CDR3 regions was selected by the immunodominant epitope (EBNA4 416-424, designated IVT). Distinct patterns of interaction with the A11–peptide complex were revealed for each AVF- or IVT-specific TCR clonotype by alanine scanning mutagenesis analysis. Blocking of cytotoxic function by antibodies specific for the CD8 coreceptor indicated that, while AVF-specific TCRs are of high affinity, the oligoclonal response to the IVT epitope includes both low- and high-affinity TCRs. Thus, comparison of the memory response to two epitopes derived from the same viral antigen and presented through the same MHC class I allele suggests that immunodominance may correlate with the capacity to maintain a broad TCR repertoire.
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| 65. |
- Djerbi, M, et al.
(författare)
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The inhibitor of death receptor signaling, FLICE-inhibitory protein defines a new class of tumor progression factors
- 1999
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Ingår i: The Journal of experimental medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 190:7, s. 1025-1031
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Tidskriftsartikel (refereegranskat)abstract
- Death receptor–mediated apoptosis can be modulated by several antiapoptotic proteins, such as the FLICE (FADD [Fas-associated death domain]-like IL-1β–converting enzyme)-inhibitory proteins (FLIPs). The FLIP family includes both cellular and viral members. The Kaposi's sarcoma–associated herpesvirus protein (KSHV)-FLIP is expressed by human herpesvirus 8 (HHV-8), which is associated with malignancies such as Kaposi's sarcoma and certain lymphomas. In this paper, we demonstrate that KSHV-FLIP protects cells from Fas-mediated apoptosis by inhibiting caspase activation and permits clonal growth in the presence of death stimuli in vitro. Furthermore, we show that KSHV-FLIP can act as a tumor progression factor by promoting tumor establishment and growth in vivo. When injected into immunocompetent recipient mouse strains, murine B lymphoma cells (A20) transduced with KSHV-FLIP rapidly develop into aggressive tumors showing a high rate of survival and growth. The tumor-progressive activity of KSHV-FLIP is mediated by prevention of death receptor–induced apoptosis triggered by conventional T cells. Consequently, inhibitors of death receptor signaling can be regarded as a new class of tumor progression factors, and HHV-8–associated tumors may represent naturally occurring examples of the tumorigenic effect of such inhibitors.
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| 66. |
- Du, Likun, et al.
(författare)
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Cernunnos influences human immunoglobulin class switch recombination and may be associated with B cell lymphomagenesis
- 2012
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 209:2, s. 291-305
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Tidskriftsartikel (refereegranskat)abstract
- Cernunnos is involved in the nonhomologous end-joining (NHEJ) process during DNA double-strand break (DSB) repair. Here, we studied immunoglobulin (Ig) class switch recombination (CSR), a physiological process which relies on proper repair of the DSBs, in B cells from Cernunnos-deficient patients. The pattern of in vivo generated CSR junctions is altered in these cells, with unusually long microhomologies and a lack of direct end-joining. The CSR junctions from Cernunnos-deficient patients largely resemble those from patients lacking DNA ligase IV, Artemis, or ATM, suggesting that these factors are involved in the same end-joining pathway during CSR. By screening 269 mature B cell lymphoma biopsies, we also identified a somatic missense Cernunnos mutation in a diffuse large B cell lymphoma sample. This mutation has a dominant-negative effect on joining of a subset of DNA ends in an in vitro NHEJ assay. Translocations involving both Ig heavy chain loci and clonal-like, dynamic IgA switching activities were observed in this tumor. Collectively, our results suggest a link between defects in the Cernunnos-dependent NHEJ pathway and aberrant CSR or switch translocations during the development of B cell malignancies.
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| 67. |
- Du, LK, et al.
(författare)
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Involvement of Artemis in nonhomologous end-joining during immunoglobulin class switch recombination
- 2008
-
Ingår i: The Journal of experimental medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 205:13, s. 3031-3040
-
Tidskriftsartikel (refereegranskat)abstract
- DNA double-strand breaks (DSBs) introduced in the switch (S) regions are intermediates during immunoglobulin class switch recombination (CSR). These breaks are subsequently recognized, processed, and joined, leading to recombination of the two S regions. Nonhomologous end-joining (NHEJ) is believed to be the principle mechanism involved in DSB repair during CSR. One important component in NHEJ, Artemis, has however been considered to be dispensable for efficient CSR. In this study, we have characterized the S recombinational junctions from Artemis-deficient human B cells. Sμ–Sα junctions could be amplified from all patients tested and were characterized by a complete lack of “direct” end-joining and a remarkable shift in the use of an alternative, microhomology-based end-joining pathway. Sμ–Sγ junctions could only be amplified from one patient who carries “hypomorphic” mutations. Although these Sμ–Sγ junctions appear to be normal, a significant increase of an unusual type of sequential switching from immunoglobulin (Ig)M, through one IgG subclass, to a different IgG subclass was observed, and the Sγ–Sγ junctions showed long microhomologies. Thus, when the function of Artemis is impaired, varying modes of CSR junction resolution may be used for different S regions. Our findings strongly link Artemis to the predominant NHEJ pathway during CSR.
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| 68. |
- Du, X., et al.
(författare)
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Mevalonate metabolism-dependent protein geranylgeranylation regulates thymocyte egress
- 2020
-
Ingår i: The Journal of experimental medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 217:2
-
Tidskriftsartikel (refereegranskat)abstract
- Thymocyte egress is a critical determinant of T cell homeostasis and adaptive immunity. Despite the roles of G protein–coupled receptors in thymocyte emigration, the downstream signaling mechanism remains poorly defined. Here, we report the discrete roles for the two branches of mevalonate metabolism–fueled protein prenylation pathway in thymocyte egress and immune homeostasis. The protein geranylgeranyltransferase Pggt1b is up-regulated in single-positive thymocytes, and loss of Pggt1b leads to marked defects in thymocyte egress and T cell lymphopenia in peripheral lymphoid organs in vivo. Mechanistically, Pggt1b bridges sphingosine-1-phosphate and chemokine-induced migratory signals with the activation of Cdc42 and Pak signaling and mevalonate-dependent thymocyte trafficking. In contrast, the farnesyltransferase Fntb, which mediates a biochemically similar process of protein farnesylation, is dispensable for thymocyte egress but contributes to peripheral T cell homeostasis. Collectively, our studies establish context-dependent effects of protein prenylation and unique roles of geranylgeranylation in thymic egress and highlight that the interplay between cellular metabolism and posttranslational modification underlies immune homeostasis.
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| 69. |
- Eleme, K., et al.
(författare)
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Cell surface organization of stress-inducible proteins ULBP and MICA that stimulate human NK cells and T cells via NKG2D
- 2004
-
Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 199:7, s. 1005-1010
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Tidskriftsartikel (refereegranskat)abstract
- Cell surface proteins major histocompatibility complex (MHC) class I-related chain A (MICA) and UL16-binding proteins (ULBP) 1, 2, and 3 are up-regulated upon infection or tumor transformation and can activate human natural killer (NK) cells. Patches of cross-linked raft resident ganglioside GM1 colocalized with ULBP1, 2, 3, or MICA, but not CD45. Thus, ULBPs and MICA are expressed in lipid rafts at the cell surface. Western blotting revealed that glycosylphosphatidylinositol (GPI)-anchored ULBP3 but not transmembrane MICA, MHC class I protein, or transferrin receptor, accumulated in detergent-resistant membranes containing GM1. Thus, MICA may have a weaker association with lipid rafts than ULBP3, yet both proteins accumulate at an activating human N-K cell immune synapse. Target cell lipid rafts marked by green fluorescent protein-tagged GPI also accumulate with ULBP3 at some synapses. Electron microscopy reveals constitutive clusters of ULBP at the cell surface. Regarding a specific molecular basis for the organization of these proteins, ULBP1, 2, and 3 and MICA are lipid modified. ULBP1, 2, and 3 are GPI anchored, and we demonstrate here that MICA is S-acylated. Finally, expression of a truncated form of MICA that lacks the putative site for S-acylation and the cytoplasmic tall can be expressed at the cell surface, but is unable to activate NK cells.
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| 70. |
- Enervald, E, et al.
(författare)
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A regulatory role for the cohesin loader NIPBL in nonhomologous end joining during immunoglobulin class switch recombination
- 2013
-
Ingår i: The Journal of experimental medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 210:12, s. 2503-2513
-
Tidskriftsartikel (refereegranskat)abstract
- DNA double strand breaks (DSBs) are mainly repaired via homologous recombination (HR) or nonhomologous end joining (NHEJ). These breaks pose severe threats to genome integrity but can also be necessary intermediates of normal cellular processes such as immunoglobulin class switch recombination (CSR). During CSR, DSBs are produced in the G1 phase of the cell cycle and are repaired by the classical NHEJ machinery. By studying B lymphocytes derived from patients with Cornelia de Lange Syndrome, we observed a strong correlation between heterozygous loss-of-function mutations in the gene encoding the cohesin loading protein NIPBL and a shift toward the use of an alternative, microhomology-based end joining during CSR. Furthermore, the early recruitment of 53BP1 to DSBs was reduced in the NIPBL-deficient patient cells. Association of NIPBL deficiency and impaired NHEJ was also observed in a plasmid-based end-joining assay and a yeast model system. Our results suggest that NIPBL plays an important and evolutionarily conserved role in NHEJ, in addition to its canonical function in sister chromatid cohesion and its recently suggested function in HR.
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