Analysis of the functional domains of herpes simplex virus type 1 immediate-early polypeptide Vmw110

At the onset of infection by herpes simplex virus type 1 (HSV-1) in tissue culture, five immediate-early (IE) genes are expressed. At least four of the IE gene products have some role in the transcriptional regulation of later classes of viral genes. This study concerns the product of IE gene 1, Vmw110. Several laboratories have shown that a cloned copy of IE gene 1 can stimulate gene expression in trans in transfection experiments; this transactivation can occur either with Vmw110 by itself or in a strongly synergistic fashion with the product of IE gene 3, Vmw175. As an approach to study the mechanism of this effect, a large number of in-frame insertion mutations in the Vmw110 coding region have been constructed. The effect of the insertions on the ability of Vmw110 to activate transcription in the presence of Vmw175 has been described. This report concerns the effect of the insertions on the ability of Vmw110 to activate gene expression in the absence of Vmw175. In addition, a family of in-frame deletion mutations has been constructed and tested in transfection and immunofluorescence assays. The results show (1) that mutations in different domains of the Vmw110 polypeptide can have different effects on function in the presence or absence of Vmw175; (2) that mutations can affect the pattern of immunofluorescent intranuclear staining of Vmw110; and (3) that deletions in the region of a particular highly basic region of the polypeptide result in failure of Vmw110 to be transported into the nucleus.