Epstein-Barr virus nuclear protein 2 transactivates a cis-acting CD23 DNA element

Abstract

Epstein-Barr virus (EBV) nuclear protein 2 (EBNA-2) is essential for B-lymphocyte growth transformation. EBNA-2 upregulates mRNAs encoding CD23, a B-lymphocyte surface protein closely associated with EBVinduced growth transformation. To further investigate this EBNA-2 effect, we searched in the genomic DNA spanning the type a and type b CD23 mRNA start sites for a cis-acting fragment that would render a promoter transactivatable by EBNA-2. An 800-bp CD23 DNA fragment (-335 to +465 relative to the type a CD23 mRNA start site) conferred EBNA-2 responsiveness to the herpes simplex virus thymidine kinase (TK) promoter when transfected into EBV-negative B-lymphoma cells. Deletional analysis identified a-275/-89 subfragment that was EBNA-2 responsive when cloned in either orientation and at variable distances upstream of the heterologous promoter. EBNA-2 and the cis-acting CD23 element increased TK-promoted mRNA and did not alter the herpes simplex virus TK promoter transcription start site. As expected, a type a CD23 promoter (-335/+80) which contained the EBNA-2-responsive element was transactivated by EBNA-2. As in EBV infection and stable EBNA-2 transfection, the CD23 DNA element in cis with heterologous or homologous promoters was less responsive to type 2 than to type 1 EBNA-2, whereas the EBNA-2-responsive DNA fragment from the EBV latent membrane protein 1 promoter was more responsive to the type 2 EBNA-2. These experiments delineate a 186-bp, EBNA-2-responsive cell DNA fragment and provide firm evidence that EBNA-2 transactivates transcription of cell genes. The greater type 1 versus type 2 EBNA-2 responsiveness of the CD23 promoter and the lack of a similar effect on the latent membrane protein 1 promoter is consistent with the hypothesis that greater cell gene transactivation by type 1 EBNA-2 is the basis for the more efficient growthtransforming properties of type 1 EBV.

CD23/FcεRII: molecular multi-tasking

“…The CD23 gene has two transcription initiation sites and differential usage of these sites and alternate splicing of RNA transcripts gives rise to two distinct protein isoforms, CD23a and CD23b [55], which differ by six or seven amino acids in the N-terminal cytoplasmic domain of the protein in both murine and human systems (Figs 1 and 4). In broad terms, CD23a is expressed constitutively in B cells while transcription of the CD23b isoform is subject to up-regulation following Epstein-Barr virus (EBV) infection [56], stimulation by IL-4 in B cells [57] or monocytes [12] or by engagement of CD40 on B cells [58]. Elements in the human CD23a and CD23b promoters that are responsive to defined stimuli (e.g.…”

DNA of lymphoma‐associated herpesvirus (HVMF1) in SIV‐infected monkeys (Macaca fascicularis) shows homologies to EBNA‐1, ‐2 and ‐5 genes

“…EBV-LMP1 inserts in the cell membrane and also induces a whole array of cellular genes (Wang et al, 1991). We were unable in a previous study (Li et al, 1993) to detect immunoreactivity for EBV LMPl in the HVMF1-carrying cells, using 2 monoclonal antibodies (MAbs), S12 and CS1-4.…”

“…In Southern blotting, a homologous DNA region was also detected by a probe covering the right part of the BYRF1-exon. EBNA2 has been shown to be necessary for initiation of EBV-induced immortalization (Cohen et al, 1989), to induce the viral LMP1, the NFkB transcription factor and several cellular proteins, in particular the CD 21-CD 23 complex, which may serve as an autocrine growth factor of EBV-infected B cells (Wang et aL, 1990(Wang et aL, , 1991. It is of interest that a CD23 cross-reacting protein was also found in most monkey lymphomas (Li et al, 1993).…”

Immune regulation in Epstein-Barr virus-associated diseases.

“…Sequential analysis of latent-gene expression following EBV infection in B lymphocytes in vitro suggests that EBNA2 and EBNA5 are the first nuclear antigens expressed (3). EBNA2 trans activates cellular genes such as CD21, CD23, c-fgr and viral genes, including those encoding LMP1 and LMP2 (1,3,37,58,59,246,251,252). Within 48 h of primary B-cell infection in vitro, all EBNA proteins have reached the level that is maintained consistently through latent infection (4,152).…”