The localization of histone H3.3 in germ line chromatin of Drosophila males as established with a histone H3.3-specific antiserum.

A rabbit antiserum, specific for the histone H3.3 replacement variant, was raised with the aid of a histone H3.3-specific peptide. Immuno blot experiments demonstrated the specificity of this polyclonal antiserum. In addition, we showed on immuno blots that two monoclonal antibodies isolated from mice with systemic lupus erythematosus (SLE) display strong reactivity with the H3.3 histone, but not with its replication-dependent counterparts. Our observations indicate that histone H3.3 might play a role as autoantigen in SLE. We used the histone H3.3-specific antiserum to characterize the germ line chromatin in cytological preparations of Drosophila testes, because our previous studies had shown that a histone H3.3-encoding gene is strongly expressed in the germ line of Drosophila males. The antiserum reacted with some of the lampbrush loops in spermatocytes and with chromatin of the postmeiotic germ cells of males. Our data indicate that histone H3.3 is not evenly distributed throughout the chromatin of germ cells, but is concentrated in distinct regions. Histone H3.3 disappears from the spermatid nuclei, along with the other core histones, during the late stages of spermatogenesis. In Drosophila polytene chromosomes, however, a rather uniform distribution of the histone H3.3 was observed. The possible role of histone H3.3 is discussed.