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  • American Society of Hematology  (5)
  • National Academy of Sciences  (4)
  • 1
    Publication Date: 2015-11-09
    Description: The dicistrovirus intergenic region internal ribosome entry site (IRES) adopts a triple-pseudoknotted RNA structure and occupies the core ribosomal E, P, and A sites to directly recruit the ribosome and initiate translation at a non-AUG codon. A subset of dicistrovirus IRESs directs translation in the 0 and +1 frames to produce the viral structural proteins and a +1 overlapping open reading frame called ORFx, respectively. Here we show that specific mutations of two unpaired adenosines located at the core of the three-helical junction of the honey bee dicistrovirusIsraeli acute paralysis virus(IAPV) IRES PKI domain can uncouple 0 and +1 frame translation, suggesting that the structure adopts distinct conformations that contribute to 0 or +1 frame translation. Using a reconstituted translation system, we show that ribosomes assembled on mutant IRESs that direct exclusive 0 or +1 frame translation lack reading frame fidelity. Finally, a nuclear magnetic resonance/small-angle X-ray scattering hybrid approach reveals that the PKI domain of the IAPV IRES adopts an RNA structure that resembles a complete tRNA. The tRNA shape-mimicry enables the viral IRES to gain access to the ribosome tRNA-binding sites and form intermolecular contacts with the ribosome that are necessary for initiating IRES translation in a specific reading frame.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 2
    Publication Date: 2019-03-19
    Description: Maternal infection during pregnancy increases risk of neurodevelopmental disorders such as schizophrenia and autism spectrum disorder (ASD) in offspring. In rodents, maternal immune activation (MIA) yields offspring with schizophrenia- and ASD-like behavioral abnormalities. Soluble epoxide hydrolase (sEH) plays a key role in inflammation associated with neurodevelopmental disorders. Here we found higher levels of sEH in the prefrontal cortex (PFC) of juvenile offspring after MIA. Oxylipin analysis showed decreased levels of epoxy fatty acids in the PFC of juvenile offspring after MIA, supporting increased activity of sEH in the PFC of juvenile offspring. Furthermore, expression of sEH (orEPHX2) mRNA in induced pluripotent stem cell-derived neurospheres from schizophrenia patients with the 22q11.2 deletion was higher than that of healthy controls. Moreover, the expression ofEPHX2mRNA in postmortem brain samples (Brodmann area 9 and 40) from ASD patients was higher than that of controls. Treatment with 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea (TPPU), a potent sEH inhibitor, in juvenile offspring from prenatal day (P) 28 to P56 could prevent cognitive deficits and loss of parvalbumin (PV) immunoreactivity in the medial PFC of adult offspring after MIA. In addition, dosing of TPPU to pregnant mothers from E5 to P21 could prevent cognitive deficits, and social interaction deficits and PV immunoreactivity in the medial prefrontal cortex of juvenile offspring after MIA. These findings suggest that increased activity of sEH in the PFC plays a key role in the etiology of neurodevelopmental disorders in offspring after MIA. Therefore, sEH represents a promising prophylactic or therapeutic target for neurodevelopmental disorders in offspring after MIA.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2016-03-14
    Description: Depression is a severe and chronic psychiatric disease, affecting 350 million subjects worldwide. Although multiple antidepressants have been used in the treatment of depressive symptoms, their beneficial effects are limited. The soluble epoxide hydrolase (sEH) plays a key role in the inflammation that is involved in depression. Thus, we examined here the role of sEH in depression. In both inflammation and social defeat stress models of depression, a potent sEH inhibitor, TPPU, displayed rapid antidepressant effects. Expression of sEH protein in the brain from chronically stressed (susceptible) mice was higher than of control mice. Furthermore, expression of sEH protein in postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, was higher than controls. This finding suggests that increased sEH levels might be involved in the pathogenesis of certain psychiatric diseases. In support of this hypothesis, pretreatment with TPPU prevented the onset of depression-like behaviors after inflammation or repeated social defeat stress. Moreover, sEH KO mice did not show depression-like behavior after repeated social defeat stress, suggesting stress resilience. The sEH KO mice showed increased brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor TrkB in the prefrontal cortex, hippocampus, but not nucleus accumbens, suggesting that increased BDNF-TrkB signaling in the prefrontal cortex and hippocampus confer stress resilience. All of these findings suggest that sEH plays a key role in the pathophysiology of depression, and that epoxy fatty acids, their mimics, as well as sEH inhibitors could be potential therapeutic or prophylactic drugs for depression.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2018-05-07
    Description: Parkinson’s disease (PD) is characterized as a chronic and progressive neurodegenerative disorder, and the deposition of specific protein aggregates of α-synuclein, termed Lewy bodies, is evident in multiple brain regions of PD patients. Although there are several available medications to treat PD symptoms, these medications do not prevent the progression of the disease. Soluble epoxide hydrolase (sEH) plays a key role in inflammation associated with the pathogenesis of PD. Here we found that MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced neurotoxicity in the mouse striatum was attenuated by subsequent repeated administration of TPPU, a potent sEH inhibitor. Furthermore, deletion of the sEH gene protected against MPTP-induced neurotoxicity, while overexpression of sEH in the striatum significantly enhanced MPTP-induced neurotoxicity. Moreover, the expression of the sEH protein in the striatum from MPTP-treated mice or postmortem brain samples from patients with dementia of Lewy bodies (DLB) was significantly higher compared with control groups. Interestingly, there was a positive correlation between sEH expression and phosphorylation of α-synuclein in the striatum. Oxylipin analysis showed decreased levels of 8,9-epoxy-5Z,11Z,14Z-eicosatrienoic acid in the striatum of MPTP-treated mice, suggesting increased activity of sEH in this region. Interestingly, the expression of sEH mRNA in human PARK2 iPSC-derived neurons was higher than that of healthy control. Treatment with TPPU protected against apoptosis in human PARK2 iPSC-derived dopaminergic neurons. These findings suggest that increased activity of sEH in the striatum plays a key role in the pathogenesis of neurodegenerative disorders such as PD and DLB. Therefore, sEH may represent a promising therapeutic target for α-synuclein–related neurodegenerative disorders.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 2004-06-15
    Description: The cells of hematopoietic and vascular endothelial cell lineages are believed to share a common precursor, termed hemangioblast. However, the existence of a growth factor acting relatively specifically on hemangioblasts remains unclear. Here we report the identification of hemangiopoietin (HAPO), a novel growth factor acting on both hematopoietic and endothelial cell lineages. In vitro in the human system, recombinant human HAPO (rhHAPO) significantly stimulated the proliferation and hematopoietic and/or endothelial differentiation of human bone marrow mononuclear cells and of purified CD34+, CD133+, kinase domain receptor-positive (KDR+), or CD34+/KDR+ cell populations. In the murine system, rhHAPO stimulated the proliferation of long-term culture-initiating cells (LTC-ICs) as well as CD34+ and stem cell antigen-1 (Sca-1+) cell subsets. In vivo, subcutaneous injection of rhHAPO into normal mice resulted in a significant increase in bone marrow hematopoietic cells. Furthermore, irradiated mice injected with rhHAPO had an enhanced survival rate and accelerated hematopoiesis. Our data suggest that HAPO is a novel growth factor acting on the primitive cells of both hematopoietic and endothelial cell lineages and that HAPO may have a clinical potential in the treatment of various cytopenias and radiation injury and in the expansion of hematopoietic and endothelial stem/progenitor cells. (Blood. 2004;103:4449-4456)
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 6
    Publication Date: 2020-11-05
    Description: The mitochondria of hematopoietic stem cell (HSC) play crucial roles in regulating cell fate and in preserving HSC functionality and survival. However, the mechanism underlying its regulation remain poorly understood. Here, we identify transcription factor TWIST1 as a novel regulator of HSC maintenance through modulating mitochondrial function. We demonstrate that Twist1 deletion results in a significantly decreased long-term HSC (LT-HSC) frequency, markedly reduced dormancy and self-renewal capacities and skewed myeloid differentiation in steady-state hematopoiesis. Twist1-deficient LT-HSC are more compromised in tolerance of irradiation and 5 fluorouracil-induced stresses, and exhibit typical phenotypes of senescence and higher levels of DNA damage and apoptosis. Mechanistically, Twist1 deficiency upregulates the expression of voltage-gated calcium channel Cacna1b in HSC, leading to noticeable increases in mitochondrial calcium levels, biogenesis, metabolic activity and reactive oxygen species production. Suppression of voltage-gated calcium channel by a calcium channel blocker largely rescues the phenotypic and functional defects in Twist1-deleted HSCs under both steady-state and stress conditions. Collectively, our data, for the first time, characterize TWIST1 as a critical regulator of HSC function acting through CACNA1B/Ca2+/mitochondria axis, and highlight the importance of Ca2+ in HSC maintenance. These observations provide new insights into the mechanisms for the control of HSC fate. Disclosures No relevant conflicts of interest to declare.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
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  • 7
    Publication Date: 2021-02-22
    Description: Mitochondria of hematopoietic stem cells (HSCs) play crucial roles in regulating cell fate and preserving HSC functionality and survival. However, the mechanism underlying its regulation remains poorly understood. Here, we identify transcription factor TWIST1 as a novel regulator of HSC maintenance through modulating mitochondrial function. We demonstrate that Twist1 deletion results in a significantly decreased lymphoid-biased (Ly-biased) HSC frequency, markedly reduced HSC dormancy and self-renewal capacities, and skewed myeloid differentiation in steady-state hematopoiesis. Twist1-deficient HSCs are more compromised in tolerance of irradiation and 5-fluorouracil-induced stresses, and exhibit typical phenotypes of senescence. Mechanistically, Twist1 deletion induces transactivation of voltage-gated calcium channel (VGCC) Cacna1b which exhausts Ly-biased HSCs, impairs genotoxic hematopoietic recovery, and enhances mitochondrial calcium levels, metabolic activity, and reactive oxygen species production. Suppression of VGCC by a calcium channel blocker largely rescues the phenotypic and functional defects in Twist1-deleted HSCs under both steady-state and stress conditions. Collectively, our data, for the first time, characterize TWIST1 as a critical regulator of HSC function acting through the CACNA1B/Ca2+/mitochondria axis, and highlight the importance of Ca2+ in HSC maintenance. These observations provide new insights into the mechanisms for the control of HSC fate.
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    Electronic ISSN: 1528-0020
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  • 8
    Publication Date: 2020-11-05
    Description: Macrophages are important member in tissue microenvironments and play diverse physiologic and pathologic roles. Leukemia associated macrophages (LAM) are a kind of specifically activated macrophages in leukemia microenvironment, which are different from M1, M2 and TAMs. We have reported the heterogeneities in gene expression profiles of LAMs. However, MicroRNA expression profiles of LAMs and regulatory mechanism are still unknown. Here, a MLL-AF9 induced mouse acute myeloid leukemia (AML) model was used, and LAMs in the spleen and bone marrow were sorted for microRNA sequencing. The microRNA expression profiles of LAMs in bone marrow and spleen in AML mice were different from macrophages from control mice. Based on the volcano plot, more than 100 microRNAs were differentially expressed in LAMs compared with macrophages in control mice. Next, five differentially expressed microRNAs were selected and verified by qRT-PCR in LAMs from spleen. The results showed that miR-451a and miR-155-5p in spleen LAMs were significantly upregulated in LAMs from spleen. Overexpression of miR-451a altered the morphology of macrophages, enhanced the phagocytic ability of macrophages, and promotes the expression of macrophage differentiation marker CD11b. Furthermore, overexpression of miR-451a had little effect on M0 macrophages, but increased the proliferation capacity of macrophages upon stimulation toward M1 or M2 phenotype. MiR-451a overexpressed-macrophages had higher level of iNOS when stimulated with LPS or IL-4 whereas there was no difference in the expression of IL-1β, IL-6, CD206 and Arg-1 between MiR-451a overexpressed-macrophages and control macrophage. Therefore, our data revealed the characteristics of the microRNA expression profile of LAMs for the first time, and verified the effect of miR-451a on macrophage in vitro. Disclosures No relevant conflicts of interest to declare.
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  • 9
    Publication Date: 2021-05-04
    Description: Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy for which there is an unmet need for novel treatment strategies. Here, we characterize the growth arrest and DNA damage-inducible gene gamma (GADD45g) as a novel tumor suppressor in AML. We show that GADD45g is preferentially silenced in AML, especially in AML with FMS-like tyrosine kinase 3–internal tandem duplication (FLT3-ITD) mutations and mixed-lineage leukemia (MLL)-rearrangements, and reduced expression of GADD45g is correlated with poor prognosis in patients with AML. Upregulation of GADD45g impairs homologous recombination DNA repair, leading to DNA damage accumulation, and dramatically induces apoptosis, differentiation, and growth arrest and increases sensitivity of AML cells to chemotherapeutic drugs, without affecting normal cells. In addition, GADD45g is epigenetically silenced by histone deacetylation in AML, and its expression is further downregulated by oncogenes FLT3-ITD and MLL-AF9 in patients carrying these genetic abnormalities. Combination of the histone deacetylase 1/2 inhibitor romidepsin with the FLT3 tyrosine kinase inhibitor AC220 or the bromodomain inhibitor JQ1 exerts synergistic antileukemic effects on FLT3-ITD+ and MLL-AF9+ AML, respectively, by dually activating GADD45g. These findings uncover hitherto unreported evidence for the selective antileukemic role of GADD45g and provide novel strategies for the treatment of FLT3-ITD+ and MLL-AF9+ AML.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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