Epstein-Barr virus nuclear protein 3C modulates transcription through interaction with the sequence-specific DNA-binding protein J kappa

Abstract

The Epstein-Barr virus (EBV) nuclear protein 3C (EBNA 3C) is essential for EBV-mediated transformation of primary B lymphocytes, is turned on by EBNA 2, and regulates transcription of some of the viral and cellular genes which are regulated by EBNA 2. EBNA 2 is targeted to response elements by binding to the DNA sequence-specific, transcriptional repressor protein J. We now show that EBNA 3C also binds to J. EBNA 3C causes J to not bind DNA or EBNA 2. J DNA binding activity in EBV-transformed lymphoblastoid cells is consequently reduced. More than 10% of the EBNA 3C coimmunoprecipitated with J from extracts of non-EBV-infected B lymphoblasts that had been stably converted to EBNA 3C expression. EBNA 3C in nuclear extracts from these cells (or in vitro-translated EBNA 3C) prevented J from interacting with a high-affinity DNA binding site. Under conditions of transient overexpression in B lymphoblasts, EBNA 2 and EBNA 3C associated with J and less EBNA 2 associated with J when EBNA 3C was coexpressed in the same cell. EBNA 3C had no effect on the activity of a ؊512/؉40 LMP1 promoter-CAT reporter construct that has two upstream J sites, but it did inhibit EBNA 2 transactivation of this promoter. These data are compatible with a role for EBNA 3C as a ''feedback'' down modulator of EBNA 2-mediated transactivation. EBNA 3C could, in theory, also activate transcription by inhibiting the interaction of the J repressor with its cognate DNA. The interaction of two viral transcriptional regulators with the same cell protein may reflect an unusually high level of complexity or stringency in target gene regulation.

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.

“…The number of replicating cells may be equal to the number of dying cells under these conditions. This effect of the ER-EBNA2 fusion protein on BJAB cells may be explained by the assumption that EBNA2 is inhibiting proliferation when expressed at an unselectedly high level (transfected cells express a non-functional fusion protein in the absence of estrogen), or that the EBNA2 function has to be balanced by other viral gene products such as, for example, EBNA3C (Le Roux et al, 1994;Marshall and Sample, 1995;Robertson et al, 1995) or LMP1 in order to promote proliferation. The observation that EBNA2 is down-regulating IgM expression as well as c-myc expression in cells with a t(8; 14) translocation not only provides an explanation for the apparent inefficiency of using EBV-transformed cells for monoclonal antibody (mAb) production, it also has important implications for the role of EBV in the development of lymphomas in immunocompromised individuals as well as BL.…”

“…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). Even though the transformation of primary B cells in vitro is strictly dependent on EBNA2 (Cohen et al, 1989;Hammerschmidt and Sugden, 1989;Kempkes et al, 1995), EBNA2 appears not to be expressed in BL tumors (Rowe et al, 1986), Hodgkin's disease (Kanavaros et al, 1993) and nasopharyngeal carcinoma (Fahraeus et al, 1988;Young et al, 1988), thus questioning its role in the development of these malignancies in vivo.…”

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

“…EBNA2 binds to the repression domain of CBF1, blocking repression function, and relief of repression combined with the presence of the strong EBNA2 transcriptional activation domain transactivates expression of genes containing upstream CBF1 binding sites (24). Two of the other essential immortalizing proteins, EBNA-3A and EBNA-3C, also bind to CBF1 (4,52,53,69). The interaction domain on CBF1 for these proteins lies amino terminal to that for EBNA2.…”

Epstein‐Barr virus infection and human malignancies

“…EBNA3B transactivates the CD40 and the vimentin promoters (Silins & Sculley 1994). The EBNA3 proteins can bind to RBP-Jk and therefore inhibit EBNA2 binding to RBP-Jk (Robertson et al 1995;Robertson et al 1996). The interplay between EBNA2 and the EBNA3 family therefore builds a network that allows precise modulation of the EBV target genes.…”