Herpes Simplex Virus 1 DNA Cleavage/Packaging: The U28 Gene Encodes a Minor Component of B Capsids

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