Localization of Antigenic Sites on Human Cytomegalovirus Virion Structural Proteins Encoded by UL48 and UL56

Bradshaw, Peggy; Duran-Guarino, M. R.; Perkins, Susan; Rowe, Judy; Fernández, J; Fry, Kirk E.; Reyes, Gregory R.; Young, Lucy H.; Foung, Steven K. H.

doi:10.1006/viro.1994.1648

Cited by 17 publications

(16 citation statements)

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“…Originally termed the HMWP, its incorporation into virions was known prior to establishing that it was the product of the UL48 gene (20,50). It is also found in NIEPS and dense bodies (9) and is incorporated at approximately 1,400 copies per virion (192).…”

Section: Pul48 (Hmwp)mentioning

confidence: 99%

Tegument Proteins of Human Cytomegalovirus

Kalejta

2008

Microbiol Mol Biol Rev

163

149

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SUMMARY Human cytomegalovirus (HCMV) is a common, medically relevant human herpesvirus. The tegument layer of herpesvirus virions lies between the genome-containing capsids and the viral envelope. Proteins within the tegument layer of herpesviruses are released into the cell upon entry when the viral envelope fuses with the cell membrane. These proteins are fully formed and active and control viral entry, gene expression, and immune evasion. Most tegument proteins accumulate to high levels during later stages of infection, when they direct the assembly and egress of progeny virions. Thus, viral tegument proteins play critical roles at the very earliest and very last steps of the HCMV lytic replication cycle. This review summarizes HCMV tegument composition and structure as well as the known and speculated functions of viral tegument proteins. Important directions for future investigation and the challenges that lie ahead are identified and discussed.

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Section: Pul48 (Hmwp)mentioning

confidence: 99%

Tegument Proteins of Human Cytomegalovirus

Kalejta

2008

Microbiol Mol Biol Rev

163

149

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“…The open reading frame (ORF) UL48-encoded protein of HCMV, pUL48, is the largest inner tegument protein that is closely associated with the capsid (6,7). A deletion of the UL48 gene is lethal to the virus (8), and viruses containing an insertion of a transposon within the upstream region of the UL48 ORF show severely impaired viral growth (9), suggesting that the function of UL48 is critical for the viral replication cycle to be successful.…”

mentioning

confidence: 99%

Involvement of the N-Terminal Deubiquitinating Protease Domain of Human Cytomegalovirus UL48 Tegument Protein in Autoubiquitination, Virion Stability, and Virus Entry

Kim

Kwon

et al. 2016

J Virol

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Human cytomegalovirus (HCMV) protein pUL48 is closely associated with the capsid and has a deubiquitinating protease (DUB) activity in its N-terminal region. Although this DUB activity moderately increases virus replication in cultured fibroblast cells, the requirements of the N-terminal region of pUL48 in the viral replication cycle are not fully understood. In this study, we characterized the recombinant viruses encoding UL48(⌬DUB/NLS), which lacks the DUB domain and the adjacent nuclear localization signal (NLS), UL48(⌬DUB), which lacks only the DUB, and UL48(⌬360 -1200), which lacks the internal region (amino acids 360 to 1200) downstream of the DUB/NLS. While ⌬DUB/NLS and ⌬360 -1200 mutant viruses did not grow in fibroblasts, the ⌬DUB virus replicated to titers 100-fold lower than those for wild-type virus and showed substantially reduced viral gene expression at low multiplicities of infection. The DUB domain contained ubiquitination sites, and DUB activity reduced its own proteasomal degradation in trans. Deletion of the DUB domain did not affect the nuclear and cytoplasmic localization of pUL48, whereas the internal region (360 -1200) was necessary for cytoplasmic distribution. In coimmunoprecipitation assays, pUL48 interacted with three tegument proteins (pUL47, pUL45, and pUL88) and two capsid proteins (pUL77 and pUL85) but the DUB domain contributed to only pUL85 binding. Furthermore, we found that the ⌬DUB virus showed reduced virion stability and less efficiently delivered its genome into the cell than the wild-type virus. Collectively, our results demonstrate that the N-terminal DUB domain of pUL48 contributes to efficient viral growth by regulating its own stability and promoting virion stabilization and virus entry. IMPORTANCEHCMV pUL48 and its herpesvirus homologs play key roles in virus entry, regulation of immune signaling pathways, and virion assembly. The N terminus of pUL48 contains the DUB domain, which is well conserved among all herpesviruses. Although studies using the active-site mutant viruses revealed that the DUB activity promotes viral growth, the exact role of this region in the viral life cycle is not fully understood. In this study, using the mutant virus lacking the entire DUB domain, we demonstrate that the DUB domain of pUL48 contributes to viral growth by regulating its own stability via autodeubiquitination and promoting virion stability and virus entry. This report is the first to demonstrate the characteristics of the mutant virus with the entire DUB domain deleted, which, along with information on the functions of this region, is useful in dissecting the functions associated with pUL48. H uman cytomegalovirus (HCMV) belongs to the Betaherpesvirus subfamily. HCMV infection is usually asymptomatic and causes latent or persistent infections in healthy people. However, congenital infection and reactivation from latent infection in immunocompromised individuals can cause severe disease (1). The HCMV virion is composed of an icosahedral capsid containing a 235-kb linea...

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“…The inner tegument layer is comprised of those tegument proteins that most closely associate with the capsid. These proteins are thus thought to be important for the stability of the capsid (6, 7) and for its proper trafficking within the cell (8,9).…”

mentioning

confidence: 99%

“…One of these inner tegument proteins of HCMV is the large tegument protein pUL48 (also referred to as high-molecularweight protein [HMWP]), which is highly conserved among herpesviruses (8,9). It is the largest tegument protein of HCMV, with a size of 2,241 amino acids and a molecular mass of about 253 kDa (2,8,10).…”

mentioning

confidence: 99%

Nuclear Targeting of Human Cytomegalovirus Large Tegument Protein pUL48 Is Essential for Viral Growth

Brock¹,

Krüger²,

Mertens³

et al. 2013

J Virol

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We report the identification of a functional nuclear localization signal (NLS) in the human cytomegalovirus (HCMV) large tegument protein pUL48 that is required for nuclear localization in transfected cells and is essential for viral growth. The NLS was mapped to pUL48 amino acid residues 284 to 302. This sequence contains a bipartite NLS comprising two clusters of basic residues (bC1 and bC2) separated by 9 amino acids. Deletion or mutation of bC1 or mutation of bC2 abrogated the nuclear localization of full-length pUL48 in transiently expressing cells, thus strongly implying a bipartite character of the NLS. Nuclear localization could be restored by fusion of a functional NLS together with enhanced green fluorescent protein (EGFP) to the N terminus of these mutants. In HCMV-infected cells, pUL48 was found in both nuclear and cytoplasmic fractions, supporting a function of the NLS during virus infection. NLS mutant viruses, generated by markerless bacterial artificial chromosome mutagenesis, were not viable in cell culture, whereas coexpression of pUL48 complemented growth of these mutants. The fusion of a functional NLS to the N terminus of pUL48 in a nonviable NLS mutant virus partially rescued the growth defect. Furthermore, the replacement of the bipartite pUL48 NLS by the monopartite pUL36 NLS of herpes simplex virus 1 supported viral growth to some extent but still revealed a severe defect in focus formation and release of infectious virus particles. Together, these results show that nuclear targeting of pUL48 is mediated by a bipartite NLS whose function is essential for HCMV growth.

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Localization of Antigenic Sites on Human Cytomegalovirus Virion Structural Proteins Encoded by UL48 and UL56

Cited by 17 publications

References 0 publications

Tegument Proteins of Human Cytomegalovirus

Tegument Proteins of Human Cytomegalovirus

Involvement of the N-Terminal Deubiquitinating Protease Domain of Human Cytomegalovirus UL48 Tegument Protein in Autoubiquitination, Virion Stability, and Virus Entry

Nuclear Targeting of Human Cytomegalovirus Large Tegument Protein pUL48 Is Essential for Viral Growth

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