Two hnRNP-associated proteins share common structural features with the adenoviral 72-kDa protein

Using our anti-hnRNP monoclonal antibody library Y. Lutz, M. Jacob, and J.-P. Fuchs (1988) Exp. Cell Res., 175, 108-124; P. Mähl, Y. Lutz, E. Puvion, and J.-P. Fuchs, (1989) J. Cell Biol. 109, 1921-1935, we investigated by immunocytofluorescence the fate of a series of speckled-distributed nuclear antigens, after HeLa cells were infected with adenovirus type 2. Although the speckled pattern, which corresponds to the nucleoplasmic fibrillogranular network, including the interchromatin-granule clusters, was still observed during most of the infectious cycle, several antibodies also revealed additional, increasingly fluorescent virus-induced structures. In noninfected cells, two of these antibodies, termed 3F2 and 2A5, recognize two antigens of 33 and 31 kDa, respectively. Western blot analysis showed that this increasing amount of fluorescence observed in infected cells did not reflect an accumulation of the 33- and 31-kDa antigens, but is actually due to the fact that both antibodies also recognize the multifunctional adenovirus 72-kDa single-stranded DNA-binding protein (DBP). Immunoelectron microscopy analyses, including sequential double-labeling, indeed showed that this additional signal precisely colocalizes with the viral 72-kDa DBP, which essentially accumulates over the entire surface of the virus-induced single-stranded DNA accumulation sites. Taken together, our data show that two host-specific hnRNP-associated antigens share common epitopes with the viral 72-kDa DBP.