During chromatin-regulated processes, the histone H2A-H2B heterodimer functions dynamically in and out of the nucleosome. Although detailed crystal structures of nucleosomes have been established, that of the isolated full-length H2A-H2B heterodimer has remained elusive. Here, we have determined the solution structure of human H2A-H2B by NMR coupled with CS-Rosetta. H2A and H2B each contain a histone fold, comprising four α-helices and two β-strands (α1–β1–α2–β2–α3–αC), together with the long disordered N- and C-terminal H2A tails and the long N-terminal H2B tail. The N-terminal αN helix, C-terminal β3 strand, and 310 helix of H2A observed in the H2A-H2B nucleosome structure are disordered in isolated H2A-H2B. In addition, the H2A α1 and H2B αC helices are not well fixed in the heterodimer, and the H2A and H2B tails are not completely random coils. Comparison of hydrogen-deuterium exchange, fast hydrogen exchange, and {1H}-15N hetero-nuclear NOE data with the CS-Rosetta structure indicates that there is some conformation in the H2A 310 helical and H2B Lys11 regions, while the repression domain of H2B (residues 27–34) exhibits an extended string-like structure. This first structure of the isolated H2A-H2B heterodimer provides insight into its dynamic functions in chromatin.

No abstract

Aminomethylenehelicene oligomers up to the (M)‐heptamer were synthesized by reductive amination from a formylhelicene building block. The oligomers containing more than three helicenes formed a double helix in 1,3‐dilfuorobenzene. The (M)‐tetramer and (M)‐pentamer unfolded into a random coil by heating to 60 °C, whereas the (M)‐hexamer only slightly unfolded at the same temperature. A two‐sided thermal hysteresis was detected in the structural change of the (M)‐tetramer and (M)‐pentamer during cooling and heating. The (M)‐pentamer and (M)‐hexamer unfolded with the addition of trifluoroacetic acid and regenerated a double helix with the addition of triethylamine.

Since many malignancies often occur in patients with smoldering type adult T-cell leukemia (ATL) (5 of 18 cases in this report), the relationship between HTLV-I (human T-cell leukemia virus type I) infection, which is closely associated with ATL, with other malignancies in an HTLV-I endemic area was examined. Among the 394 patients with malignancies and who had not had blood cell transfusions, 61 (15.5%) tested positive for HTLV-I antibody. The prevalence was significantly higher in males older than age 40 years and females of all ages compared to age- and sex-matched healthy individuals. The overall seroprevalence (26.1%) in 291 patients with malignancies and who had had blood cell transfusions was higher than that of those who had not had blood transfusions. There was no significant correlation between the site of malignancy and antibody prevalence. These results suggest the possibility that development of malignancy may contribute to expression of latent HTLV-I infection and that HTLV-I infection may contribute to the risk of other malignancies.

Background Inducible co-stimulator (ICOS), a member of the CD28 family of costimulatory molecules, is induced on CD4+ and CD8+ T-cells following their activation. ICOS functions as an essential immune regulator and ICOS blockade is a potential approach to immune modulation in allogeneic transplantation. Here, we describe the expression profile of ICOS in dogs and determine whether ICOS expression is up-regulated during chronic graft versus host disease (GVHD) and host versus graft (HVG) reactions in the canine hematopoietic cell transplantation model. Methods Monoclonal antibodies against cell surface-expressed ICOS were produced and tested in vitro for suppression of canine mixed leukocyte reactions (MLR). Expression of ICOS on CD3+ cells was evaluated by flow cytometry using peripheral blood, lymph nodes and splenocytes obtained from dogs undergoing GVH and HVG reactions. Results Canine ICOS was expressed in an inducible pattern on T-cells activated by Con A, anti-CD3 mAb in combination with anti-CD28 mAb, and alloantigen stimulation. Immunosuppressive effects of ICOS blockade were observed in MLR using peripheral blood mononuclear cells from dog-leukocyte-antigen-nonidentical dogs. Immunosuppressive effects of ICOS blockade were observed in MLR when anti-ICOS was combined with suboptimal concentrations of cytotoxic T-lymphocyte antigen 4-Ig (CTLA4-Ig) or cyclosporine. ICOS expression was significantly up-regulated on T-cells in dogs undergoing graft rejection or chronic GVHD after allogeneic hematopoietic cell transplantation. Conclusion These studies suggest that ICOS plays a role in graft rejection and GVHD in an out-bred animal model, and ICOS blockade may be an approach to prevention and treatment of chronic GVHD.