Distinctions between bovine herpesvirus 1 and herpes simplex virus type 1 VP22 tegument protein subcellular associations

The alphaherpesvirus tegument protein VP22 has been characterized with mult iple traits including microtubule reorganization, nuclear localization, and nonclassical intercellular trafficking. However, all these data were deriv ed from studies using herpes simplex virus type 1 (HSV-1) and may not apply to VP22 homologs of other alphaherpesviruses. We compared subcellular attr ibutes of HSV-1 VP22 (HVP22) with bovine herpesvirus 1 (BHV-1) VP22 (BVP22) using green fluorescent protein (GFP)-fused VP22 expression vectors. Fluor escence microscopy of cell lines transfected with these constructs revealed differences as well as similarities between the two VP22 homologs. Compare d to that of HVP22, the BVP22 microtubule interaction was much less pronoun ced. The VP22 nuclear interaction varied,,vith a marbled or halo appearance for BVP22 and a speckled or nucleolus-bound appearance for HVP22: Both VP2 2 homologs associated with chromatin at various stages of mitosis and could traffic from expressing cells to the nuclei of nonexpressing cells. Howeve r, distinct qualitative differences in microtubule, nuclear, and chromatin association as well as trafficking were observed. The differences in VP22 h omolog characteristics revealed in this study will help define VP22 functio n within HSV-1 and BHV-1 infection.