Disease relevance of EBNA-3B/EBNA-3C

• Analysis of EBV polymorphisms demonstrated that before CTL infusion, more than one virus was present, including a virus with wild-type EBNA-3B [1].
• 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 [2].
• However, the EBNA3B gene in nasal lymphoma tissues exhibited predominantly the prototype A sequence [3].

High impact information on EBNA-3B/EBNA-3C

• 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 [4].
• Since deletion of EBNA-3B has no significant impact on B-cell immortalization in tissue culture, this finding suggested that EBNA-3B-mediated regulation of CXCR4 may be an important viral strategy for alteration of B-cell homing in the infected host [5].
• EBNA-3B- and EBNA-3C-Regulated Cellular Genes in Epstein-Barr Virus-Immortalized Lymphoblastoid Cell Lines [5].
• Two of these isolates could potentially express truncated EBNA-3B products, and, similarly, we now show that the third isolate, IB4, has a point mutation and in-frame deletion of 263 amino acids [6].
• 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) [7].

Chemical compound and disease context of EBNA-3B/EBNA-3C

• 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 [8].

Biological context of EBNA-3B/EBNA-3C

• Recombinant Epstein-Barr viruses with a stop codon inserted into the nuclear protein 3B (EBNA 3B) open reading frame were generated by second-site homologous recombination [9].
• In order to test whether a virus with EBNA-3B completely deleted can immortalize B-cell growth, we first cloned the EBV genome as a bacterial artificial chromosome (BAC) and showed that the BAC-derived virus was B-cell immortalization competent [6].
• Computer analyses identified four potential nuclear-localization signals (NLSs) in the EBNA3B amino acid sequence [10].
• The nucleotide sequence of Epstein-Barr virus (EBV) nuclear antigen (EBNA)-2 and EBNA-3B regions of an EBV-2 isolate in Japan was analyzed [11].
• The remarkably well-conserved sequence seems to suggest that the structure of the EBNA-2 and EBNA-3B genes of EBV-2 is crucial for their function in virus replication [11].

Anatomical context of EBNA-3B/EBNA-3C

• These data indicate that the EBNA 3B protein is not critical for primary B-lymphocyte infection, growth transformation, or lytic virus infection in vitro [9].
• No difference was noted between mutant and wild-type recombinants, derived in parallel, in latent (other than EBNA 3B) or lytic cycle-infected cell virus protein expression or in the growth of the latently infected transformed cell lines [9].
• A sixth Epstein-Barr virus nuclear protein (EBNA3B) is expressed in latently infected growth-transformed lymphocytes [12].
• These EBNA3B CTL epitopes in the normal Japanese population and in 2 lymphoid neoplasias, pyothorax-associated lymphoma (PAL) and nasal natural killer-cell lymphoma, were directly sequenced by PCR [3].

Associations of EBNA-3B/EBNA-3C with chemical compounds

• 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 [13].

Other interactions of EBNA-3B/EBNA-3C

• 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 [14].
• The fusion is from EBV coordinate 80299 within the BMRF1 sequence to coordinate 90998 in the EBNA3B sequence [8].
• Furthermore, activation of the LMP-1 promoter is a unique function of EBNA-3C, not shared by EBNA-3A and EBNA-3B [15].

Analytical, diagnostic and therapeutic context of EBNA-3B/EBNA-3C

• Western immunoblotting and immunofluorescence experiments using human 293 cells showed that the recombinant plasmid is capable of expressing a protein with a size, immunological characteristics, and a subcellular localization indistinguishable from those of native B95-8 EBNA3B [16].
• Because PAL cells expressed EBNA3B mRNA, detected by RT-PCR, but nasal lymphoma cells did not, mutations and strain differences of the sequences of EBNA3B CTL epitopes were specific findings in EBNA3B-positive lymphomas [3].
• By utilizing fusion proteins with EGFP, deletion constructs of EBNA3B and site-directed mutagenesis, three of the four NLSs (aa 160-166, 430-434 and 867-873) were shown to be functional in truncated forms of EBNA3B, whilst an additional NLS (aa 243-246) was identified within the N-terminal region of EBNA3B [10].

References