Identification and Characterization of the UL24 Gene Product of Herpes Simplex Virus Type 2

The UL24 gene of herpes simplex virus type 2 (HSV-2) is predicted to encode a 281 amino acid protein with a molecular mass of 30.5kDa. In this study, the HSV-2 UL24 gene product has been identified by using a rabbit polyclonal antiserum produced against a recombinant protein containing the full-length UL24 gene product of HSV-2 fused to glutathione-S-transferase. The antiserum reacted specifically with a 32kDa protein in HSV-2 186-infected Vero cells and with 31 and 32kDa proteins in UL24-expressing Cos-7 cells. Accumulation of UL24 protein to detectable levels required viral DNA synthesis, indicating that the protein was regulated as a late gene. UL24 protein was found to be associated with purified HSV-2 virions and C capsids. Indirect immunofluorescence analysis demonstrated that the UL24-specific fluorescence was detected in perinuclear regions of the cytoplasm and/or in the nucleus as small discrete granules from 9h post infection (hpi). Furthermore, the UL24 protein expressed singly was detected predominantly in the nucleus and slightly in the cytoplasm at 24h after transfection, with branch-like cytoplasmic protruding structures. Strong nucleolus staining was visible in partial cells.