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EMBO Press is an editorially independent publishing platform for the development of EMBO scientific publications.

Having developed a genetic procedure to expose a foreign epitope at the surface of Escherichia coli by using the outer membrane LamB protein as a carrier, we apply this procedure to express two distinct portions of the preS2 region of hepatitis B virus: region A, residues 132-145, and region B, residues 153-171. The resulting hybrid proteins (LamB-preS2 A and LamB-preS2 B) were normally expressed, stable, and still kept most biologic functions of LamB. The corresponding bacterial strains were used directly as immunogens in rabbits and mice. Both viral sequences were found to be immunogenic in the two animal species. With LamB-preS2 A, antibodies induced were able to react with the viral particles and the immobilized peptide. With LamB-preS2 B, the antibodies raised were not able to recognize the immobilized peptide. However, the results suggest that the B epitope, inserted in LamB, was at least as efficient as the corresponding synthetic peptide in raising antiviral antibodies. Thus, epitope presentation with LamB may present advantages for immunization. We also have shown that peptide A is an essential part of the polymerized human serum albumin receptor. These results, which validate further the LamB vector system for epitope presentation, provide information on the two hepatitis B regions expressed.

We studied the enrichment and distribution of the histone variant mH2A1 in the condensed inactive X (Xi) chromosome. By using highly specific antibodies against mH2A1 and stable HEK 293 cell lines expressing either green fluorescent protein (GFP)-mH2A1 or GFP-H2A, we found that the Xi chromosome contains approximately 1.5-fold more mH2A1 than the autosomes. To determine the in vivo distribution of mH2A1 along the X chromosome, we used a native chromatin immunoprecipitation-on-chip technique. DNA isolated from mH2A1-immunoprecipitated nucleosomes from either male or female mouse liver were hybridized to tiling microarrays covering 5 kb around most promoters or the entire X chromosome. The data show that mH2A1 is uniformly distributed across the entire Xi chromosome. Interestingly, a stronger mH2A1 enrichment along the pseudoautosomal X chromosome region was observed in both sexes. Our results indicate a potential role for macroH2A in large-scale chromosome structure and genome stability.