EBNA-2 transactivates a lymphoid-specific enhancer in the BamHI C promoter of Epstein-Barr virus

Abstract

Among the few Epstein-Barr virus (EBV) genes expressed during latency are the Epstein-Barr nuclear antigens (EBNAs), at least one of which contributes to the ability of the virus to transform B lymphocytes. We have analyzed a promoter located in the BamHI-C fragment of EBV which is responsible for the expression of EBNA-1 in some cell lines. Deletion analysis of a 1.4-kb region 5' of the RNA start site has identified a 700-bp fragment that is required for optimal promoter activity in latently infected B lymphocytes, as shown by promoter constructs linked to the chloramphenicol acetyltransferase reporter gene. This fragment is also able to enhance activity, in an orientation-independent manner, of the simian virus 40 early promoter linked to the chloramphenicol acetyltransferase gene. The enhancer element has some constitutive activity in EBV-negative lymphoid cells, which is increased in the presence of the EBNA-2 gene product. Further deletions have shown that the EBNA-2-responsive region requires a 98-bp region that contains a degenerate octamer-binding motif. In epithelial cells there was no enhancer activity regardless of the presence of EBNA-2. These results demonstrate that BamHI-C promoter activity may be dependent not on an enhancer contained in the ori-P, as was previously assumed, but rather on EBNA-2 transactivation of this more proximal enhancer located in the upstream region of the BamHI C promoter itself.

Epstein-Barr virus latent membrane protein (LMP1) is not sufficient to maintain proliferation of B cells but both it and activated CD40 can prolong their survival.

“…transactivates the viral promoters of three latent membrane antigens (LMP1, LMP2A and LMP2B) and the Cp promoter, which regulates the expression of EBV nuclear antigens (Fahraeus et al, 1990a;Sung et al, 1991;Zimber-Strobl et al, 1991;Laux et al, 1994b). EBNA2 does not bind to DNA directly (Ling et al, 1993;Zimber-Strobl et al, 1993) but interacts with the cellular DNA binding proteins RBP-JK and PU.…”

Epstein-Barr virus immortalization: Notch2 interacts with CBF1 and blocks differentiation

“…EBNA-2 is required for both initiation and initial maintenance of immortalization (32). EBNA2 is a transcriptional activator that regulates EBNA latency gene expression from the C promoter (28,46,58,67) and expression of both the LMP-1 and LMP-2 genes (29,70). EBNA2 also contributes to the activation of expression of cellular genes such as those encoding the B-cell activation markers CD21 and CD23 and the cell cycle regulator cyclin D2 (6,32,44,57,63).…”

Epstein-Barr virus nuclear antigen 2 is a transcriptional suppressor of the immunoglobulin mu gene: implications for the expression of the translocated c-myc gene in Burkitt's lymphoma cells.

“…It appears in two allelic forms (EBNA2A and EBNA2B) in natural isolates which share -50% homology (Zimber et al, 1986). EBNA2, together with EBNA-LP, is the first viral gene expressed after infection of primary B cells, and is a transcriptional activator of latent viral as well as cellular genes (CD21, CD23 and c-fgr) (Calender et al, 1987;Wang et al, 1987;Abbot et al, 1990;Cordier et al, 1990;Fahraeus et al, 1990;Ghosh and Kieff, 1990;Knutson, 1990;Sung et al, 1991;Woisetschlaeger et al, 1991;Zimber-Strobl et al, 1991Jin and Speck, 1992;Ling et al, 1993;Laux et al, 1994a;Meitinger et al, 1994). EBNA2 has been shown to exert its transactivating function, at least in part, by binding to a ubiquitously expressed cellular protein, RBP-JK, which binds to DNA in a sequence-specific manner (Grossmann et al, 1994;Henkel et al, 1994;Waltzer et al, 1994;Zimber-Strobl et al, 1994), and through interaction with transcription factors of the ets gene family (Spi-1, PU-1) (Laux et al, 1994b;Johannsen et al, 1995).…”