TRANSCRIPTIONAL REPRESSION BY THE EPSTEIN-BARR-VIRUS EBNA3A PROTEIN TETHERED TO DNA DOES NOT REQUIRE RBP-J(KAPPA)

The Epstein-Barr virus (EBV) proteins EBNA1, EBNA2, EBNA3A, EBNA3C, LM P1 and EBNA-LP are essential for the in vitro immortalization of prima ry B lymphocytes by EBV. EBNA2 is a transcriptional activator of viral and cellular genes. Both EBNA3A and EBNA3C have been shown to specifi cally inhibit EBNA2-activated transcription by direct interaction with RBP-JK, a cellular DNA-binding factor known to recruit EBNA2 to EBNA2 -responsive genes. This interaction interferes with the binding of RBP -JK to DNA in vitro, and this is probably the mechanism by which EBNA3 A and EBNA3C repress EBNA2-activated transcription in vivo. EBNA3A and EBNA3C also directly repress transcription when tethered to a promote r via the DNA-binding domain of the yeast Gal4 protein. As RBP-J kappa has been previously shown to be a repressor in mam malian cells, this repression could be due to the recruitment of RBP-J kappa by Gal4-EBN A3A and 3C. In this study, we have precisely mapped the domain of EBNA 3A involved in the interaction with RBP-JK and we have shown that inte raction with RBP-IK is not required for the Gal4-EBNA3A-mediated repre ssion. Furthermore, we have characterized in EBNA3A a domain of 143 am ino acids which is necessary and sufficient for EBNA3A-dependent repre ssion.