Bovine herpesvirus 1 tegument protein VP22 interacts with histones, and the carboxyl terminus of VP22 is required for nuclear localization

The bovine herpesvirus 1(BHV-1) UL49 gene encodes a viral tegument protein termed VP22. UL49 homologs are conserved among alphaherpesviruses. Interest ingly, the BHV-1 VP22 deletion mutant virus is asymptomatic and avirulent i n infected cattle but produces only a slight reduction in titer in vitro. A ttenuation of the BHV-1 VP22 deletion mutant virus in vivo suggests that VP 22 plays a functional role in BHV-1 replication. In herpes simplex virus ty pe 1, the VP22 homolog was previously shown to interact with another tegume nt protein,VP16, the alpha -transinducing factor in vitro. In this report, we show that (i) the nuclear targeting of VP22 is independent of other vira l factors, (ii) the carboxyl terminus of VP22 is required for its nuclear l ocalization, (iii) VP22 associates with histones and nucleosomes, (iv) an a ntihistone monoclonal antibody cross-reacts with VP22, and (v) acetylation of histone H4 is decreased in VP22-expressing cells as well as virus-infect ed cells. Our data suggest that VP22 may have a modulatory function during BHV-1 infection.