Characterization of the U(L)33 gene product of herpes simplex virus 1

The U(L)33 protein is one of six genes (including U(L)6, U(L)15, U(L)17, U( L)28, and U(L)32) required for cleavage of viral concatemeric DNA into unit -length genomes and packaging of the virus genomes into preformed capsids. The U(L)25 gene product is dispensable for cleavage of viral DNA but essent ial for packaging of DNA into capsids. A polyclonal antiserum was produced against an affinity-purified protein containing the full-length U(L)33 gene product of herpes simplex Virus 1 fused to glutathione-S-transferase. A pr otein of approximate M-r 19,000 that reacted with the antiserum was detecte d in immunoblots of herpes simplex virus 1-infected cellular lysates. This protein was not detected in lysates of mock-infected cells or cells infecte d with a mutant virus containing a stop codon in U(L)33, indicating that th e 19,000 M-r protein is the product of the U(L)33 open reading frame. The U (L)33 gene product was not detected in purified virions or capsids. Accumul ation of the U(L)33 protein to detectable levels required viral DNA synthes is, indicating that the protein was regulated as a late gene. Indirect immu nofluorescence analysis demonstrated that U(L)33 protein accumulated predom inantly within replication compartments in the central domains of infected cell nuclei and within the cytoplasm. Localization of the U(L)33 gene produ ct in replication compartments was maintained in cells infected with a vari ety of cleavage/packaging mutants. (C) 2000 Academic Press.