Disease relevance of EBNA-3A

• Two Epstein-Barr virus (EBV) types are known, EBV1 and EBV2, which possess substantially diverged alleles for latency genes EBNA-2, EBNA-3A, EBNA-3B and EBNA-3C but are thought to be otherwise similar [1].
• Mature DCs pulsed with either live or inactivated vaccinia EBNA-3A virus could elicit strong EBNA-3A-specific CTLs [2].
• To determine the biological significance of the interaction of EBNA-3A with Jkappa, we have studied its conservation in the simian lymphocryptovirus herpesvirus papio (HVP) by cloning HVP-3A, the homolog of EBNA-3A encoded by this virus [3].
• No expression of EBNA-1, EBNA-2, or EBNA-3A RNA was detected in the oral hairy leukoplakia cDNA library [4].
• We now show that EBNA3A and EBNA3B expressed in non-EBV-infected Burkitt tumor lymphoblasts are similar to EBNA3C in binding to glutathione S-transferase-RBPJkappa in vitro and in coimmunoprecipitating from cell lysates with antibody to RBPJkappa [5].

High impact information on EBNA-3A

• The dramatic reversal of EBV-driven lymphoproliferations in bone marrow transplant patients following CTL infusion demonstrates the potential of this approach, and here we discuss prospects for its extension to other EBV-positive tumors in which the immunodominant EBNA3A, 3B, 3C proteins are not expressed [6].
• During these experiments, we identified a new human leukocyte antigen-A3-restricted EBNA-3A epitope, residues 603-611, RLRAEAGVK [7].
• Vaccinia recombinants encoding EBNA 3A and EBNA 3C were recognized more frequently than any other vaccinia recombinants used in this study, while no CTL epitopes were localized in EBNA 1 [8].
• WT EBNA3C expression from an oriP plasmid transfected into E3C-HT LCLs protected the LCLs from growth arrest in medium without 4HT, whereas expression of EBNA3A or EBNA3B did not [9].
• Two naturally occurring EBV variants (EBV types 1 and 2) differ extensively in their growth-transformation phenotype and in their EBNA-LP, EBNA-2, and EBNA-3A, -3B, and -3C genes [10].

Chemical compound and disease context of EBNA-3A

• This deletion encodes major EBV genes involved in both infection and transformation of human primary B lymphocytes and includes the glycoprotein gp350, the entire open reading frame of EBNA3A, and the amino-terminal region of EBNA3B [11].

Biological context of EBNA-3A

• Recombinant Epstein-Barr viruses (EBV) with a translation termination codon mutation inserted into the nuclear protein 3A (EBNA-3A) or 3C (EBNA-3C) open reading frame were generated by second-site homologous recombination [12].
• Consistent with this binding, EBNA-3A inhibited reporter gene expression from plasmids containing RBP-Jk DNA binding sites within their promoters, including the Cp promoter [13].
• Using a reporter gene assay based on the recruitment of Jkappa by various regions spanning EBNA-3A, we have shown that this mutation abolished binding of Jkappa to the N-proximal region (amino acids 125 to 222) and that no other region of EBNA-3A alone was sufficient to mediate an association with Jkappa [3].
• There appears to be a gene activation function within EBNA-3A that is masked in the full-length protein in this assay [13].
• Epstein-Barr virus (EBV) nuclear antigen 3A (EBNA-3A) is essential for virus-mediated immortalization of B lymphocytes in vitro and is believed to regulate transcription of cellular and/or viral genes [3].

Anatomical context of EBNA-3A

• In unselected, HLA-B8(+) donors, monocyte-derived mature DCs were pulsed with the HLA-B8-restricted EBNA-3A peptide, FLRGRAYGL, and added to autologous T cells for 7 days at a DC:T ratio of 1:5 to 1:60 [2].
• The cultured cells specifically lysed EBNA-3A peptide-pulsed, HLA-B8(+), B-lymphoblastoid cell lines in a 5-hour (51)Cr-release assay [2].
• Induction of Epstein-Barr virus-specific cytotoxic T-lymphocyte responses using dendritic cells pulsed with EBNA-3A peptides or UV-inactivated, recombinant EBNA-3A vaccinia virus [2].
• EBNA-3 (also called EBNA-3A) is one of the EBV encoded nuclear antigens that are necessary for B-cell transformation [14].
• EBNA3A has been reported to have one nuclear-localization signal and is targeted to the nucleus during transformation, where it associates with components of the nuclear matrix [15].

Associations of EBNA-3A with chemical compounds

• A mutant EBNA-3A protein in which alanine residues were substituted for amino acids 199, 200, and 202 no longer downregulated transcription [3].
• Here we show that EBNA3A binds CtBP both in vitro and in vivo but that this interaction does not require a near consensus (98)PLDLR(102) motif in the NH(2) terminus of EBNA3A [16].
• Wild-type (wt) EBNA3A expressed in the LCLs specifically sustained growth under nonpermissive conditions, whereas EBNA3B or EBNA3C expression had no effect (S. Mauro, E. Johannsen, D. Illanes, A. Cooper, and E. Kieff, J. Virol. 77:10437-10447, 2003) [17].
• Wild-type EBNA3A expression from an oriP plasmid transfected into the LCLs protected the EBNA3AHT-infected LCLs from growth arrest and death in medium without 4HT, whereas EBNA3B or EBNA3C expression was unable to protect the LCLs from growth arrest and death [18].

Regulatory relationships of EBNA-3A

• In a transient-expression assay, the EBNA2-activated transcription was found to be downregulated by EBNA3A, EBNA3B, and EBNA3C [19].

Other interactions of EBNA-3A

• We have also found that the behavior of EBNA-3A in a cell fractionation procedure that distinguishes insoluble matrix from soluble cell fractions is modified by EBNA-LP, indicating a further novel level of interplay between the EBNA proteins [13].
• Furthermore, we chose three known HLA-B8-restricted epitopes, RAKFKQLL (RAK), FLRGRAYGL (FLR), and QAKWRLQTL (QAK), of the lytic protein BZLF1 and the latent protein EBNA3A [20].
• Frequencies of the HLA-A3-restricted epitope RVRAYTYSK (RVR) whose minimal length was mapped in this study to amino acid position 148-156 of the immediate-early protein BRLF1 were compared with those of a further known HLA-A3-restricted epitope within EBNA3A, RLRAEAQVK (RLR) [20].

Analytical, diagnostic and therapeutic context of EBNA-3A

• By using enhanced green fluorescent protein-tagged deletion mutants of EBNA3A in combination with site-directed mutagenesis, an additional five functional nuclear-localization signals have been identified in the EBNA3A protein [15].

References