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The large tegument protein pUL36 is essential for formation of the capsid vertex-specific component at the capsid-tegument interface of herpes simplex virus 1.

Fan WH, Roberts AP, McElwee M, Bhella D, Rixon FJ, Lauder R - J. Virol. (2014)

Bottom Line: In addition, the presence of full-length pUL36 results in weak density that extends the CVSC toward the penton, suggesting either that this extra density is formed directly by pUL36 or that pUL36 stabilizes other components of the vertex-tegument interface.Herpesviruses have complex particles that are formed as a result of a carefully controlled sequence of assembly steps.We show that the largest viral protein, pUL36, which occupies the layer of tegument closest to the capsid, is essential for formation of structurally normal connections to the capsid.

View Article: PubMed Central - PubMed

Affiliation: MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom.

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CVSC densities on capsids of two unrelated UL36 deletion mutants. The icosahedrally reconstructed structure of C-capsids purified from the cytoplasm of cells infected with the UL36 deletion mutant KΔUL36 is shown radially colored (A) and superimposed on a B-capsid map (shown in gray) (B). To allow comparison, the superimposed ARΔUL36/B-capsid map from Fig. 1B is shown again as panel C. The locations of the penton (5), a peripentonal hexon (P), and a Ta and Tc triplex are marked on panel A. Each black arrowhead indicates the position of one CVSC density. Scale bar = 50 Å.
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Figure 3: CVSC densities on capsids of two unrelated UL36 deletion mutants. The icosahedrally reconstructed structure of C-capsids purified from the cytoplasm of cells infected with the UL36 deletion mutant KΔUL36 is shown radially colored (A) and superimposed on a B-capsid map (shown in gray) (B). To allow comparison, the superimposed ARΔUL36/B-capsid map from Fig. 1B is shown again as panel C. The locations of the penton (5), a peripentonal hexon (P), and a Ta and Tc triplex are marked on panel A. Each black arrowhead indicates the position of one CVSC density. Scale bar = 50 Å.

Mentions: To confirm that the smaller CVSC was directly related to the lack of pUL36, the experiment was repeated using an independent HSV-1 strain KOS mutant, KΔUL36 (26). KΔUL36 has an internal deletion which removes 3,600 bases from an internal region of the UL36 open reading frame. This incomplete deletion allows the expression of the N-terminal 361 amino acids of pUL36 (20, 26). Despite this difference, the phenotype of KΔUL36 resembles that of the complete deletion in ARΔUL36, with accumulation of cytoplasmic C-capsids but no progression to envelopment or formation of mature virions. KΔUL36 cytoplasmic C-capsids were prepared, imaged, and reconstructed to a final resolution of 19 Å using the conditions and procedures described above. Comparison with the WT B-capsid again showed additional densities at the vertices which were similar to those in ARΔUL36 and much smaller than those in WT or FRΔUL37 C-capsids (Fig. 3). The close similarities between the KΔUL36 and ARΔUL36 structures implies that the unexpectedly small size of their CVSCs is not mutant or virus strain specific but is directly related to the absence of full-length pUL36.


The large tegument protein pUL36 is essential for formation of the capsid vertex-specific component at the capsid-tegument interface of herpes simplex virus 1.

Fan WH, Roberts AP, McElwee M, Bhella D, Rixon FJ, Lauder R - J. Virol. (2014)

CVSC densities on capsids of two unrelated UL36 deletion mutants. The icosahedrally reconstructed structure of C-capsids purified from the cytoplasm of cells infected with the UL36 deletion mutant KΔUL36 is shown radially colored (A) and superimposed on a B-capsid map (shown in gray) (B). To allow comparison, the superimposed ARΔUL36/B-capsid map from Fig. 1B is shown again as panel C. The locations of the penton (5), a peripentonal hexon (P), and a Ta and Tc triplex are marked on panel A. Each black arrowhead indicates the position of one CVSC density. Scale bar = 50 Å.
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Related In: Results  -  Collection

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Figure 3: CVSC densities on capsids of two unrelated UL36 deletion mutants. The icosahedrally reconstructed structure of C-capsids purified from the cytoplasm of cells infected with the UL36 deletion mutant KΔUL36 is shown radially colored (A) and superimposed on a B-capsid map (shown in gray) (B). To allow comparison, the superimposed ARΔUL36/B-capsid map from Fig. 1B is shown again as panel C. The locations of the penton (5), a peripentonal hexon (P), and a Ta and Tc triplex are marked on panel A. Each black arrowhead indicates the position of one CVSC density. Scale bar = 50 Å.
Mentions: To confirm that the smaller CVSC was directly related to the lack of pUL36, the experiment was repeated using an independent HSV-1 strain KOS mutant, KΔUL36 (26). KΔUL36 has an internal deletion which removes 3,600 bases from an internal region of the UL36 open reading frame. This incomplete deletion allows the expression of the N-terminal 361 amino acids of pUL36 (20, 26). Despite this difference, the phenotype of KΔUL36 resembles that of the complete deletion in ARΔUL36, with accumulation of cytoplasmic C-capsids but no progression to envelopment or formation of mature virions. KΔUL36 cytoplasmic C-capsids were prepared, imaged, and reconstructed to a final resolution of 19 Å using the conditions and procedures described above. Comparison with the WT B-capsid again showed additional densities at the vertices which were similar to those in ARΔUL36 and much smaller than those in WT or FRΔUL37 C-capsids (Fig. 3). The close similarities between the KΔUL36 and ARΔUL36 structures implies that the unexpectedly small size of their CVSCs is not mutant or virus strain specific but is directly related to the absence of full-length pUL36.

Bottom Line: In addition, the presence of full-length pUL36 results in weak density that extends the CVSC toward the penton, suggesting either that this extra density is formed directly by pUL36 or that pUL36 stabilizes other components of the vertex-tegument interface.Herpesviruses have complex particles that are formed as a result of a carefully controlled sequence of assembly steps.We show that the largest viral protein, pUL36, which occupies the layer of tegument closest to the capsid, is essential for formation of structurally normal connections to the capsid.

View Article: PubMed Central - PubMed

Affiliation: MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom.

Show MeSH
Related in: MedlinePlus