Hitomi (ASTRO-H) X-ray Astronomy Satellite

The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E  >  2  keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month

Hitomi X-Ray Studies of Giant Radio Pulses from the Crab Pulsar

To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2300 keV band and the Kashima NICT radio telescope in the 1.41.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 fluctuations of the X-ray fluxes at the pulse peaks, and the 3 upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.510 keV and 70300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) 10(exp 11) erg cm(exp 2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions

Defining HIV-1 Vif residues that interact with CBFβ by site-directed mutagenesis

AbstractVif is essential for HIV-1 replication in T cells and macrophages. Vif recruits a host ubiquitin ligase complex to promote proteasomal degradation of the APOBEC3 restriction factors by poly-ubiquitination. The cellular transcription cofactor CBFβ is required for Vif function by stabilizing the Vif protein and promoting recruitment of a cellular Cullin5-RING ubiquitin ligase complex. Interaction between Vif and CBFβ is a promising therapeutic target, but little is known about the interfacial residues. We now demonstrate that Vif conserved residues E88/W89 are crucial for CBFβ binding. Substitution of E88/W89 to alanines impaired binding to CBFβ, degradation of APOBEC3, and virus infectivity in the presence of APOBEC3 in single-cycle infection. In spreading infection, NL4-3 with Vif E88A/W89A mutation replicated comparably to wild-type virus in permissive CEM-SS cells, but not in multiple APOBEC3 expressing non-permissive CEM cells. These results support a model in which HIV-1 Vif residues E88/W89 may participate in binding CBFβ

HTLV-1 bZIP factor suppresses TDP1 expression through inhibition of NRF-1 in adult T-cell leukemia

Abstract Adult T-cell leukemia (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1). We recently reported that abacavir, an anti-HIV-1 drug, potently and selectively kills ATL cells. This effect was attributed to the reduced expression of tyrosyl-DNA-phosphodiesterase 1 (TDP1), a DNA repair enzyme, in ATL cells. However, the molecular mechanism underlying the downregulation of TDP1 in ATL cells remains elusive. Here we identified the core promoter of the TDP1 gene, which contains a conserved nuclear respiratory factor 1 (NRF-1) binding site. Overexpression of NRF-1 increased TDP1-promoter activity, whereas the introduction of dominant-negative NRF-1 repressed such activity. Overexpression of NRF-1 also upregulated endogenous TDP-1 expression, while introduction of shNRF-1 suppressed TDP1 in Jurkat T cells, making them susceptible to abacavir. These results indicate that NRF-1 is a positive transcriptional regulator of TDP1-gene expression. Importantly, we revealed that HTLV-1 bZIP factor (HBZ) protein which is expressed in all ATL cases physically interacts with NRF-1 and inhibits the DNA-binding ability of NRF-1. Taken together, HBZ suppresses TDP1 expression by inhibiting NRF-1 function in ATL cells. The HBZ/NRF-1/TDP1 axis provides new therapeutic targets against ATL and might explain genomic instability leading to the pathogenesis of ATL

CKIP-1 Is an Intrinsic Negative Regulator of T-Cell Activation through an Interaction with CARMA1

<div><p>The transcription factor NF-κB plays a key regulatory role in lymphocyte activation and generation of immune response. Stimulation of T cell receptor (TCR) induces phosphorylation of CARMA1 by PKCθ, resulting in formation of CARMA1-Bcl10-MALT1 (CBM) complex at lipid rafts and subsequently leading to NF-κB activation. While many molecular events leading to NF-κB activation have been reported, it is less understood how this activation is negatively regulated. We performed a cell-based screening for negative regulators of TCR-mediated NF-κB activation, using mutagenesis and complementation cloning strategies. Here we show that casein kinase-2 interacting protein-1 (CKIP-1) suppresses PKCθ-CBM-NF-κB signaling. We found that CKIP-1 interacts with CARMA1 and competes with PKCθ for association. We further confirmed that a PH domain of CKIP-1 is required for association with CARMA1 and its inhibitory effect. CKIP-1 represses NF-κB activity in unstimulated cells, and inhibits NF-κB activation induced by stimulation with PMA or constitutively active PKCθ, but not by stimulation with TNFα. Interestingly, CKIP-1 does not inhibit NF-κB activation induced by CD3/CD28 costimulation, which caused dissociation of CKIP-1 from lipid rafts. These data suggest that CKIP-1 contributes maintenance of a resting state on NF-κB activity or prevents T cells from being activated by inadequate signaling. In conclusion, we demonstrate that CKIP-1 interacts with CARMA1 and has an inhibitory effect on PKCθ-CBM-NF-κB signaling.</p></div

PH domain of CKIP-1 is essential not only for the interaction with CARMA1 but also for the inhibitory effect on NF-κB activation.

<p>(A) Jurkat T cells were electroporated with 5 µg of each CKIP-1 truncated form together with 5 µg of κB-Luc and 0.1 µg of <i>Renilla</i>-Luc. Nineteen hours later, cells were stimulated for 5 hr upon PMA (10 ng/ml) or CD3/CD28 (2 µg/ml each). The expressed protein levels were analyzed by Western blotting. (B) Jurkat T cells were electroporated with 5 µg of each CKIP-1 truncated form together with 5 µg of PKCθ AE or Myc-CARMA1, 5 µg of κB-Luc and 0.1 µg of <i>Renilla</i>-Luc. After 24 hr, cells were lysed and luciferase activity was assessed. The expressed protein levels were analyzed by Western blotting. Values represent the average of three independent experiments and error bars represent the SD from the average.</p

Identification of CKIP-1 as a negative regulator in NF-κB activation.

<p>(A) 400 pmol of human CKIP-1-specific siRNA or non-targeting siRNA together with 5 µg of κB-Luc, 0.1 µg of <i>Renilla</i>-Luc were electroporated into Jurkat T cells. Luciferase activity was assayed after 48 hr. The reduction of endogenous CKIP-1 protein levels was analyzed by Western blotting. (B) Jurkat T cells were electroporated with human CKIP-1-specific siRNA or non-targeting siRNA using AMAXA Nucleofector System (Lonza). Thirty hours later, nuclear protein extracts were harvested and NF-κB activity was measured by TransAM NF-κB p65 chemi kit (Active Motif). The reduction of endogenous CKIP-1 protein levels was analyzed by Western blotting. (C) Jurkat T cells were transfected with 5 µg of CKIP-1 or empty vector (mock) together with 5 µg of κB-Luc and 0.1 µg of <i>Renilla</i>-Luc. Nineteen hours later, cells were stimulated for 5 hr upon CD3 (2 µg/ml), CD3/CD28 (2 µg/ml each), TNFα (20 ng/ml), PMA (10 ng/ml) or PMA (10 ng/ml) + CD28 (2 µg/ml). The expressed protein levels were analyzed by Western blotting. (D) Jurkat T cells were transfected with 5 µg of CKIP-1 or empty vector (mock). Twenty-four hours later, cells were stimulated for 30 min upon PMA (10 ng/ml). Then cells were harvested and NF-κB activity was measured by TransAM NF-κB p65 chemi kit. The expressed protein levels were analyzed by Western blotting. Values represent the average of three independent experiments and error bars represent the SD from the average.</p

Lipid rafts accumulated by CD3/CD28 costimulation do not contain CKIP-1.

<p>Jurkat T cells were stimulated for 15-CD3 (10 µg/ml) and anti-CD28 (5 µg/ml), together with 15 µg of mouse IgG. The cells were then lysed and subjected to OptiPrep density gradient centrifugation to isolate lipid rafts. Lysates were subjected to SDS-PAGE and analyzed by Western blotting.</p