When confronted with poor oxygenation, cells adapt by activating survival signaling pathways, including the oxygen-sensitive transcriptional regulators called hypoxia-inducible factor alphas ...(HIF-αs). We report here that HIF-1α also regulates the life cycle of Epstein-Barr virus (EBV). Incubation of EBV-positive gastric carcinoma AGS-Akata and SNU-719 and Burkitt lymphoma Sal and KemIII cell lines with a prolyl hydroxylase inhibitor, L-mimosine or deferoxamine, or the NEDDylation inhibitor MLN4924 promoted rapid and sustained accumulation of both HIF-1α and lytic EBV antigens. ShRNA knockdown of HIF-1α significantly reduced deferoxamine-mediated lytic reactivation. HIF-1α directly bound the promoter of the EBV primary latent-lytic switch BZLF1 gene, Zp, activating transcription via a consensus hypoxia-response element (HRE) located at nt -83 through -76 relative to the transcription initiation site. HIF-1α did not activate transcription from the other EBV immediate-early gene, BRLF1. Importantly, expression of HIF-1α induced EBV lytic-gene expression in cells harboring wild-type EBV, but not in cells infected with variants containing base-pair substitution mutations within this HRE. Human oral keratinocyte (NOK) and gingival epithelial (hGET) cells induced to differentiate by incubation with either methyl cellulose or growth in organotypic culture accumulated both HIF-1α and Blimp-1α, another cellular factor implicated in lytic reactivation. HIF-1α activity also accumulated along with Blimp-1α during B-cell differentiation into plasma cells. Furthermore, most BZLF1-expressing cells observed in lymphomas induced by EBV in NSG mice with a humanized immune system were located distal to blood vessels in hypoxic regions of the tumors. Thus, we conclude that HIF-1α plays central roles in both EBV's natural life cycle and EBV-associated tumorigenesis. We propose that drugs that induce HIF-1α protein accumulation are good candidates for development of a lytic-induction therapy for treating some EBV-associated malignancies.
The immediate-early (IE) BZLF1 gene of Epstein-Barr virus (EBV) regulates the switch between latent and lytic infection by EBV. We previously showed that the cellular transcription factor ZEB1 binds ...to a sequence element, ZV, located at nt -17 to -12 relative to the transcription initiation site of the BZLF1 promoter, Zp, repressing transcription from Zp in a transient transfection assay. Here, we report the phenotype in the context of a whole EBV genome of a variant of EBV strain B95.8 containing a 2-bp substitution mutation in the ZV element of Zp that reduced, but did not eliminate, ZEB1 binding to Zp. Strikingly, epithelial 293 cells latently infected with the EBV ZV mutant spontaneously produced IE-, early-, and late-gene products and infectious virus, while wild-type (WT)-infected 293 cells did not and have never been reported to do so. Furthermore, treatment with the chemical inducers sodium butyrate and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) led to an additional order-of-magnitude production of infectious virus in the ZV mutant-infected 293 cells, but still no virus in the WT-infected 293 cells. Similarly, ZV mutant-infected Burkitt's lymphoma BJAB cells accumulated at least 10-fold more EBV IE mRNAs than did WT-infected BJAB cells, with TPA or sodium butyrate treatment leading to an additional 5- to 10-fold accumulation of EBV IE mRNAs in the ZV mutant-infected cells. Thus, we conclude that ZEB1 binding to Zp plays a central role in regulating the latent-lytic switch in EBV-infected epithelial and B cells, suggesting ZEB1 as a target for lytic-induction therapies in EBV-associated malignancies.
•Evaluating the effectiveness of the formulas to calculate the DIF proposed by the specification for the DIF test values of UHPC.•Establishing an impact compressive model of UHPC using SHPB ...technology by calibrating the K&C model.•Supplementing and improving the DIF-strain rate curves of UHPC based on the established analysis model.•Obtaining the expressions of DIF varying in the strain rate and uniaxial compressive strength under six different specimen sizes of UHPC.
This work numerically investigates the dynamic increase factor (DIF) of ultra-high performance concrete (UHPC) under compressive impact by employing a split-Hopkinson pressure bar (SHPB). The DIF test values of UHPC are collated at six different sizes of SHPB devices, and the effectiveness of the formulas to calculate the DIF proposed by the specification for normal concrete (NC) is evaluated. An analysis model simulating the SHPB test of UHPC in the LS-DYNA is established by calibrating the Karagozian and Case concrete (K&C) model, and the DIF-strain rate curves of UHPC are further supplemented and improved. The expressions of DIF under six different specimen sizes for UHPC are obtained by regression analysis. The results indicate that (1) the proposed formulas by the specification for NC will overestimate the strain rate effect of UHPC under impact compression; (2) the calibrated K&C model can simulate well the dynamic stress–strain curve of UHPC in compression under different specimen sizes; (3) the DIF value increases with the increase of the specimen size and decreases with the increase of the uniaxial compressive strength, while the variation trends of the threshold of strain rate in the DIF-strain rate curves are opposite to those of the DIF value; (4) the proposed formulas to calculate the DIF can match well the numerical results, and avoid overestimating the DIF of UHPC to a certain extent.
•Calibrating the KCC model in LS-DYNA software for UHPC material.•Establishing an impact analysis model of UHPC using SHPB technology.•Performing a parameter study to investigate the lateral inertia ...effect of UHPC in SHPB testing.•Providing the diameter and aspect ratio (AR) of UHPC specimen under high strain rates.
The paper focuses on investigating the lateral inertia effect in dynamic impact testing of ultra-high performance concrete (UHPC) using a Split-Hopkinson pressure bar (SHPB), based on numerical analysis. The assigned material parameters of the UHPC are obtained by calibrating the parameters of the Karagozian and Case concrete (KCC) model in LS-DYNA software. An impact analysis model of UHPC using SHPB technology is established and calibrated by the test results. A parametric study is performed to estimate the influences of the diameter and aspect ratio (AR) of the UHPC specimen, and the strain rate on the lateral inertia effect in the SHPB testing. The numerical simulation results show that: (1) the impact analysis model can predict the test results of UHPC specimens using the SHPB technique with reasonable accuracy; (2) to reduce the lateral inertia effect, the suggested diameter and AR of the UHPC specimen is 0.9–0.95 times the diameter of the bar, and 0.35–0.45 at a 100 s−1 strain rate or lower, respectively; (3) the lateral inertia effect of UHPC in the SHPB testing is more noticeable with an increase in strain rate, and the diameter of the UHPC specimen is recommended to be 0.95 times the diameter of the bar, as the strain rate is higher than 100 s−1.
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