Epstein-Barr virus encoded nuclear protein EBNA-3 binds a novel human uridine kinase/uracil phosphoribosyltransferase
Epstein-Barr virus encoded nuclear protein EBNA-3 binds a novel human uridine kinase/uracil phosphoribosyltransferase
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Abstract Background Epstein-Barr virus (EBV) infects resting B-lymphocytes and transforms read more them into immortal proliferating lymphoblastoid cell lines (LCLs) in vitro.The transformed immunoblasts may grow up as immunoblastic lymphomas in immuno-suppressed hosts.Results In order to identify cellular protein targets that may be involved in Epstein-Barr virus mediated B-cell transformation, human LCL cDNA library was screened with one of the transformation associated nuclear antigens, EBNA-3 (also called EBNA-3A), using the yeast two-hybrid system.A clone encoding a fragment of a novel human protein was isolated (clone 538).The interaction was confirmed using in vitro binding assays.
A full-length cDNA clone (F538) was isolated.Sequence alignment with known proteins and 3D structure predictions suggest that F538 is a novel human uridine kinase/uracil phosphoribosyltransferase.The GFP-F538 fluorescent fusion protein showed a preferentially cytoplasmic distribution but translocated to the nucleus upon co-expression of EBNA-3.A naturally occurring splice variant of F538, that lacks the C-terminal uracil phosphoribosyltransferase part but maintain uridine kinase domain, did not translocate to the nucleus in the presence of EBNA3.Antibody that was here raised against the bacterially produced GST-538 protein showed cytoplasmic staining in EBV negative Burkitt lymphomas but gave a predominantly nuclear staining in EBV positive LCL-s and stable transfected cells expressing EBNA-3.
Conclusion We suggest that EBNA-3 by direct protein-potein interaction induces the nuclear accumulation of a novel enzyme, that is part of the ribonucleotide salvage pathway.Increased intranuclear levels of UK/UPRT may contribute to the metabolic build-up that is needed for blast transformation and rapid proliferation.