A Chromatin-remodeling Protein Is a Component of Fission Yeast Mediator

The multiprotein Mediator complex is an important regulator of RNA polymerase II-dependent genes in eukaryotic cells. In contrast to the situation in many other eukaryotes, the conserved Med15 protein is not a stable component of Mediator isolated from fission yeast. We here demonstrate that Med15 exists in a protein complex together with Hrp1, a CHD1 ATP-dependent chromatin-remodeling protein. The Med15-Hrp1 subcomplex is not a component of the core Mediator complex but can interact with the L-Mediator conformation. Deletion of med15⁺ and hrp1⁺ causes very similar effects on global steady-state levels of mRNA, and genome-wide analyses demonstrate that Med15 associates with a distinct subset of Hrp1-bound gene promoters. Our findings therefore indicate that Mediator may directly influence histone density at regulated promoters.     

Acute symptomatic gastritis due to Helicobacter heilmannii

Helicobacter heilmannii is a Gram-negative spiral-shaped organism predominantly associated with zoonotic infection. Human pathology has also been described, but acute symptoms with complete resolution have been infrequently reported. We present a 50-year-old man in whom H. heilmannii gastritis presented as an acute febrile illness and was successfully treated with antibiotics and proton pump inhibitor. Epidemiology, diagnosis, and treatment of similar cases are reviewed.     

Photoaffinity labelling with an ATP analog of the N-terminal peptide of myosin.

Photoaffinity labelling of tryptic and chymotryptic heavy meromyosin with 3′O-3-[N-(4-azido-2-nitrophenyl) amino]propionyl-adenosine 5′-triphosphate (arylazido-β-alanine ATP) resulted in incorporation of radioactivity and inhibition of the ATPase activity. ATP prevented the reaction with the photoaffinity label, as shown by the lack of incorporation of ³H and intact ATPase activity. On the tryptic digestion of either type of photoaffinity labeled HMM the label was found in a 25K peptide identifiable with the N-terminus of the myosin heavy chain (Lu et al., Fed. Proc. $\text{37}$ 1695 1978). The results are discussed in the light of previous localization of the reactive thiol groups, SH-1 and SH-2 (Balint et al., Arch. Biochem. Biophys. $\text{190}$, 793 1978).     

Primary DNA damage in human blood lymphocytes exposed in vitro to 2450 MHz radiofrequency radiation

Human peripheral blood samples collected from three healthy human volunteers were exposed in vitro to pulsed-wave 2450 MHz radiofrequency (RF) radiation for 2 h. The RF radiation was generated with a net forward power of 21 W and transmitted from a standard gain rectangular antenna horn in a vertically downward direction. The average power density at the position of the cells in the flask was 5 mW/cm(2). The mean specific absorption rate, calculated by finite difference time domain analysis, was 2.135 (+/-0.005 SE) W/kg. Aliquots of whole blood that were sham-exposed or exposed in vitro to 50 cGy of ionizing radiation from a (137)Cs gamma-ray source were used as controls. The lymphocytes were examined to determine the extent of primary DNA damage (single-strand breaks and alkali-labile lesions) using the alkaline comet assay with three different slide-processing schedules. The assay was performed on the cells immediately after the exposures and at 4 h after incubation of the exposed blood at 37 +/- 1 degrees C to allow time for rejoining of any strand breaks present immediately after exposure, i.e. to assess the capacity of the lymphocytes to repair this type of DNA damage. At either time, the data indicated no significant differences between RF-radiation- and sham-exposed lymphocytes with respect to the comet tail length, fluorescence intensity of the migrated DNA in the tail, and tail moment. The conclusions were similar for each of the three different comet assay slide-processing schedules examined. In contrast, the response of lymphocytes exposed to ionizing radiation was significantly different from RF-radiation- and sham-exposed cells. Thus, under the experimental conditions tested, there is no evidence for induction of DNA single-strand breaks and alkali-labile lesions in human blood lymphocytes exposed in vitro to pulsed-wave 2450 MHz radiofrequency radiation, either immediately or at 4 h after exposure.     

The C-terminus SH3-binding domain of Kv1.3 is required for the actin-mediated immobilization of the channel via cortactin

Kv1.3 channels play a pivotal role in the activation and migration of T-lymphocytes. These functions are accompanied by the channels'' polarization, which is essential for associated downstream events. However, the mechanisms that govern the membrane movement of Kv1.3 channels remain unclear. F-actin polymerization occurs concomitantly to channel polarization, implicating the actin cytoskeleton in this process. Here we show that cortactin, a factor initiating the actin network, controls the membrane mobilization of Kv1.3 channels. FRAP with EGFP-tagged Kv1.3 channels demonstrates that knocking down cortactin decreases the actin-based immobilization of the channels. Using various deletion and mutation constructs, we show that the SH3 motif of Kv1.3 mediates the channel immobilization. Proximity ligation assays indicate that deletion or mutation of the SH3 motif also disrupts interaction of the channel with cortactin. In T-lymphocytes, the interaction between HS1 (the cortactin homologue) and Kv1.3 occurs at the immune synapse and requires the channel''s C-terminal domain. These results show that actin dynamics regulates the membrane motility of Kv1.3 channels. They also provide evidence that the SH3 motif of the channel and cortactin plays key roles in this process.     

Improving protein structure prediction using multiple sequence-based contact predictions

Although residue-residue contact maps dictate the topology of proteins, sequence-based ab initio contact predictions have been found little use in actual structure prediction due to the low accuracy. We developed a composite set of nine SVM-based contact predictors that are used in I-TASSER simulation in combination with sparse template contact restraints. When testing the strategy on 273 nonhomologous targets, remarkable improvements of I-TASSER models were observed for both easy and hard targets, with p value by Student's t test<0.00001 and 0.001, respectively. In several cases, template modeling score increases by >30%, which essentially converts "nonfoldable" targets into "foldable" ones. In CASP9, I-TASSER employed ab initio contact predictions, and generated models for 26 FM targets with a GDT-score 16% and 44% higher than the second and third best servers from other groups, respectively. These findings demonstrate a new avenue to improve the accuracy of protein structure prediction especially for free-modeling targets.     

Sulfur K-edge XAS of WVO vs. MoVO bis(dithiolene) complexes: contributions of relativistic effects to electronic structure and reactivity of tungsten enzymes

Molybdenum- or tungsten-containing enzymes catalyze oxygen atom transfer reactions involved in carbon, sulfur, or nitrogen metabolism. It has been observed that reduction potentials and oxygen atom transfer rates are different for W relative to Mo enzymes and the isostructural Mo/W complexes. Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations on [Mo(V)O(bdt)(2)](-) and [W(V)O(bdt)(2)](-), where bdt=benzene-1,2-dithiolate(2-), have been used to determine that the energies of the half-filled redox-active orbital, and thus the reduction potentials and MO bond strengths, are different for these complexes due to relativistic effects in the W sites.     

Erthyrocyte changes in the hibernating woodchuck (Marmota monax)

Active woodchucks were maintained at 23 °C with a photoperiod of LD 12:12. Hibernating woodchucks were kept at 10 °C with a photoperiod of LD 8:16. Blood was collected and the erythrocytes were counted and measured.The data showed an increase in red blood cell count, a decrease in erythrocyte diameter and a decrease in mean corpuscular diameter during hibernation. The hematocrit was the same in both the hibernating and active woodchucks. It would appear that there are a greater number of smaller cells present in the circulation of the hibernating woodchuck as compared to that of the active woodchuck. This may result from the combined effects of increased life span, decreased destruction and continued, but slowed, production of red blood cells.