The amino-terminal C/H1 domain of CREB binding protein mediates Zta transcriptional activation of latent Epstein-Barr virus

Latent Epstein-Barr virus (EBV) is maintained as a nucleosome-covered episo me that can be transcriptionally activated by overexpression of the viral i mmediate-early protein, Zta. We show here that reactivation of latent EBV b y Zta can be significantly enhanced by coexpression of the cellular coactiv ators CREB binding protein (CBP) and p300. A stable complex containing both Zta and CBP could be isolated from lytically stimulated, but not latently infected RAJI nuclear extracts. Zta-mediated viral reactivation and transcr iptional activation were both significantly inhibited by coexpression of th e E1A 12S protein but not by an N-terminal deletion mutation of E1A (E1A De lta 2-36), which fails to bind CBP. Zta bound directly to two related cyste ine- and histidine-rich domains of CBP, referred to as C/H1 and C/H3. These domains both interacted specifically with the transcriptional activation d omain of Zta in an electrophoretic mobility shift assay. Interestingly, we found that the C/H3 domain aas a potent dominant negative inhibitor of Zta transcriptional activation function. In contrast, an amino-terminal fragmen t containing the C/H1 domain was sufficient for coactivation of Zta transcr iption and viral reactivation function. Thus, CBP can stimulate the transcr iption of latent EBV in a histone acetyltransferase-independent manner medi ated by the CBP amino-terminal C/H1-containing domain. We propose that CBP may regulate aspects of EBV latency and reactivation by integrating cellula r signals mediated by competitive interactions between C/H1, C/H3, and the Zta activation domain.