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J. Virol., Jan 1998, 142-150, Vol 72, No. 1
PM Day, RB Roden, DR Lowy and JT Schiller
We have used immunofluorescent staining and confocal microscopy to examine
the subcellular localization of structural and nonstructural bovine
papillomavirus (BPV) proteins in cultured cells that produce infectious
virions. When expressed separately, L1, the major capsid protein, showed a
diffuse nuclear distribution while L2, the minor capsid protein, was found
to localize to punctate nuclear regions identified as promonocytic leukemia
protein (PML) oncogenic domains (PODs). Coexpression of L1 and L2 induced a
relocation of L1 into the PODs, leading to the colocalization of L1 and L2.
The effect of L2 expression on the distribution of the nonstructural viral
proteins E1 and E2, which are required for maintenance of the genome and
viral DNA synthesis, was also examined. The localization of the E1 protein
was unaffected by L2 expression. However, the pattern of anti-E2 staining
was dramatically altered in L2-expressing cells. Similar to L1, E2 was
shifted from a dispersed nuclear locality into the PODs and colocalized
with L2. The recruitment of full-length E2 by L2 occurred in the absence of
other viral components. L2 was shown previously to be essential for the
generation of infectious BPV. Our present results provide evidence for a
role for L2 in the organization of virion components by recruiting them to
a distinct nuclear domain. This L2- dependent colocalization probably
serves as a mechanism to promote the assembly of papillomaviruses either by
increasing the local concentration of virion constituents or by providing
the physical architecture necessary for efficient packaging and assembly.
The data also suggest a role for a nonstructural viral protein, E2, in
virion assembly, specifically the recruitment of the viral genome to the
sites of assembly, through its high-affinity interaction with specific
sequences in the viral DNA.
Copyright © 1998, American Society for Microbiology
The papillomavirus minor capsid protein, L2, induces localization of the major capsid protein, L1, and the viral transcription/replication protein, E2, to PML oncogenic domains
Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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