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Herpes simplex virus 1 DNA cleavage/packaging: the UL28 gene encodes a minor component of B capsids
1C5169 Veterinary Education Center, Cornell University, Ithaca, New York, 14853, USA.
Abstract:
An antiserum directed against a bacterial fusion protein containing UL28 protein sequences specifically recognized an 86,000 apparent Mr protein in immunoblots of wild-type capsids. This protein was not detected in immunoblots of capsids purified from cells infected with a UL28 deletion virus, indicating that the protein was a product of UL28. The 86,000 Mr protein was also detected in capsids purified from cells infected with mutant viruses lacking the UL6, UL15, and UL25 genes, indicating that the UL28 protein can associate with capsids independently of successful DNA packaging and other minor capsid components. The UL6 protein, full-length UL15 protein, and UL25-encoded proteins were also detected in capsids purified from cells infected with the UL28 deletion virus. The UL28 and UL6 proteins remained associated with capsids treated with 1.0 M guanidine-HCl, indicating that, like the UL6 protein, the UL28 protein was an integral component of capsids. Amounts of UL28 protein were reduced in DNA-containing capsids and UL28 protein was not detected in virions, suggesting that some UL28 protein is lost during the cleavage-packaging reaction.
Insights
The UL28 protein is an integral component of viral capsids, associating independently of DNA packaging. Some UL28 protein is lost during DNA cleavage and packaging into virions.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Viral capsid assembly is crucial for viral replication.
- The precise roles of individual capsid proteins are not fully understood.
- Herpesvirus assembly involves complex protein-protein interactions.
Purpose of the Study:
- To investigate the role and association of the UL28 protein in viral capsid formation.
- To determine if UL28 is an integral capsid component.
- To understand UL28's behavior during DNA packaging.
Main Methods:
- Western blot analysis using antiserum against UL28 fusion protein.
- Purification of viral capsids from wild-type and mutant virus-infected cells.
- Treatment of capsids with guanidine hydrochloride to assess protein association.
Main Results:
- An 86,000 Mr protein, identified as a UL28 product, was detected in wild-type capsids.
- UL28 associated with capsids independently of UL6, UL15, and UL25 genes.
- UL28 remained associated with capsids after guanidine-HCl treatment, indicating integral status.
- UL28 amounts decreased in DNA-containing capsids and were absent in virions.
Conclusions:
- The UL28 protein is an integral component of herpesvirus capsids.
- UL28 association with capsids occurs independently of DNA packaging.
- UL28 is likely lost or modified during the cleavage-packaging process.