PMID:22623767

Citation	Chang, CW, Lee, CP, Huang, YH, Yang, PW, Wang, JT and Chen, MR (2012) Epstein-Barr virus protein kinase BGLF4 targets the nucleus through interaction with nucleoporins. J. Virol. 86:8072-85
Abstract	BGLF4 of Epstein-Barr virus (EBV) encodes a serine/threonine protein kinase that phosphorylates multiple viral and cellular substrates to optimize the cellular environment for viral DNA replication and the nuclear egress of viral nucleocapsids. BGLF4 is expressed predominantly in the nucleus at early and late stages of virus replication, while a small portion of BGLF4 is distributed in the cytoplasm at the late stage of virus replication and packaged into the virion. Here, we analyzed systematically the functional domains crucial for nuclear localization of BGLF4 and found that both the N and C termini play important modulating roles. Analysis of amino acid substitution mutants revealed that the C terminus of BGLF4 does not contain a conventional nuclear localization signal (NLS). Additionally, deletion of the C-terminal putative helical regions at amino acids 386 to 393 and 410 to 419 diminished the nuclear translocation of BGLF4, indicating that the secondary structure of the C terminus is important for the localization of BGLF4. The green fluorescent protein-fused wild-type or C-terminal helical regions of BGLF4 associate with phenylalanine/glycine repeat-containing nucleoporins (Nups) in nuclear envelope fractionation. Both coimmunoprecipitation and in vitro pull-down assays further demonstrated that BGLF4 binds to Nup62 and Nup153. Remarkably, nuclear import assay with permeabilized HeLa cells demonstrated that BGLF4 translocated into nucleus independent of cytosolic factors. Data presented here suggest that BGLF4 employs a novel mechanism through direct interactions with nucleoporins for its nuclear targeting.
Links	PubMed PMC3421656 Online version:10.1128/JVI.01058-12
Keywords	Active Transport, Cell Nucleus/genetics; Amino Acid Substitution; Cell Nucleus/enzymology; Cell Nucleus/genetics; Cell Nucleus/virology; DNA Replication/physiology; DNA, Viral/genetics; DNA, Viral/metabolism; Epstein-Barr Virus Infections/genetics; Epstein-Barr Virus Infections/metabolism; HeLa Cells; Herpesvirus 4, Human/physiology; Humans; Membrane Glycoproteins/genetics; Membrane Glycoproteins/metabolism; Mutation, Missense; Nuclear Pore Complex Proteins/genetics; Nuclear Pore Complex Proteins/metabolism; Protein Binding; Protein Structure, Secondary; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases/genetics; Protein-Serine-Threonine Kinases/metabolism; Viral Proteins/genetics; Viral Proteins/metabolism; Virus Assembly/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
EBVB9:KR2	part_of	GO:0042025: host cell nucleus	ECO:0000315: mutant phenotype evidence used in manual assertion		C		Seeded From UniProt	complete
EBVB9:KR2	part_of	GO:0044199: host cell nuclear envelope	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
EBVB9:KR2		GO:0042025: host cell nucleus	ECO:0000315:		C		Figure 2 demonstrates that deletions of the N- and C-terminal regions of this protein inhibit its ability to localize to the host nucleus	complete CACAO 6775
EBVB9:KR2		GO:0044199: host cell nuclear envelope	ECO:0000314:		C		Fig. 6 shows the association of the C terminus of this protein with the host nuclear envelope	complete CACAO 6800

References

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