title: The cellular localization pattern of Varicella-Zoster virus ORF29p is influenced by proteasome-mediated degradation.
abstract: Varicella-zoster virus (VZV) open reading frame 29 (ORF29) encodes a single-stranded DNA binding protein. During lytic infection, ORF29p is localized primarily to infected-cell nuclei, whereas during latency it appears in the cytoplasm of infected neurons. Following reactivation, ORF29p accumulates in the nucleus. In this report, we analyze the cellular localization patterns of ORF29p during VZV infection and during autonomous expression. Our results demonstrate that ORF29p is excluded from the nucleus in a cell-type-specific manner and that its cellular localization pattern may be altered by subsequent expression of VZV ORF61p or herpes simplex virus type 1 ICP0. In these cases, ORF61p and ICP0 induce nuclear accumulation of ORF29p in cell lines where it normally remains cytoplasmic. One cellular system utilized by ICP0 to influence protein abundance is the proteasome degradation pathway. Inhibition of the 26S proteasome, but not heat shock treatment, resulted in accumulation of ORF29p in the nucleus, similar to the effect of ICP0 expression. Immunofluorescence microscopy and pulse-chase experiments reveal that stabilization of ORF29p correlates with its nuclear accumulation and is dependent on a functional nuclear localization signal. ORF29p nuclear translocation in cultured enteric neurons and cells derived from an astrocytoma is reversible, as the protein's distribution and stability revert to the previous states when the proteasomal activity is restored. Thus, stabilization of ORF29p leads to its nuclear accumulation. Although proteasome inhibition induces ORF29p nuclear accumulation, this is not sufficient to reactivate latent VZV or target the immediate-early protein ORF62p to the nucleus in cultured guinea pig enteric neurons.
authors.affiliation: Integrated Program in Cellular, Molecular and Biophysical Studies, and Department of Microbiology, Columbia University College of Physicians and Surgeons, 701 W. 168th Street, New York, NY 10032, USA.
authors.forename: Christina L
authors.initials: CL
authors.lastname: Stallings
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Duigou
authors.forename: Anne A
authors.initials: AA
authors.lastname: Gershon
authors.forename: Michael D
authors.initials: MD
authors.lastname: Gershon
authors.forename: Saul J
authors.initials: SJ
authors.lastname: Silverstein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D017615:Enteric Nervous System / Q000378:metabolism / Q000821:virology; D005091:Exons; D006168:Guinea Pigs; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000378:metabolism; D014645:Herpesvirus 3, Human / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D016366:Open Reading Frames; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism / Q000821:virology; D046509:Tissue Culture Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D007976:Leupeptins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; C073411:protein 61, Varicella-zoster virus; D044767:Ubiquitin-Protein Ligases; C051804:Vmw110 protein, Human herpesvirus 1; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde