Herpes simplex virus 1 DNA cleavage/packaging: The U(L)28 gene encodes a minor component of B capsids

Abstract

An antiserum directed against a bacterial fusion protein containing U(L)28 protein sequences specifically recognized an 86,000 apparent M(r) protein in immunoblots of wild-type capsids. This protein was not detected in immunoblots of capsids purified from cells infected with a U(L)28 deletion virus, indicating that the protein was a product of U(L)28. The 86,000 M(r) protein was also detected in capsids purified from cells infected with mutant viruses lacking the U(L)6, U(L)15, and U(L)25 genes, indicating that the U(L)28 protein can associate with capsids independently of successful DNA packaging and other minor capsid components. The U(L)6 protein, full-length U(L)15 protein, and U(L)25-encoded proteins were also detected in capsids purified from cells infected with the U(L)28 deletion virus. The U(L)28 and U(L)6 proteins remained associated with capsids treated with 1.0 M guanidine- HCl, indicating that, like the U(L)6 protein, the U(L)28 protein was an integral component of capsids. Amounts of U(L)28 protein were reduced in DNA- containing capsids and U(L)28 protein was not detected in virions, suggesting that some U(L)28 protein is lost during the cleavage-packaging reaction.