Abstract
Reactivation of the Epstein-Barr virus from latency is dependent on expression of the BZLF1 viral immediate-early protein. The BZLF1 promoter (Zp) normally exhibits only low basal activity but is activated in response to chemical inducers such as 12-O-tetradecanoylphorbol-13-acetate and calcium ionophore. We found that Jun dimerization protein 2 (JDP2) plays a significant role in suppressing Zp activity. Reporter, EMSA, and ChIP assays of a Zp mutant virus revealed JDP2 association with Zp at the ZII cis-element, a binding site for CREB/ATF/AP-1. Suppression of Zp activity by JDP2 correlated with HDAC3 association and reduced levels of histone acetylation. Although introduction of point mutations into the ZII element of the viral genome did not increase the level of BZLF1 production, silencing of endogenous JDP2 gene expression by RNA interference increased the levels of viral early gene products and viral DNA replication. These results indicate that JDP2 plays a role as a repressor of Zp and that its replacement by CREB/ATF/AP-1 at ZII is crucial to triggering reactivation from latency to lytic replication.
Highlights
The Epstein-Barr virus (EBV)2 is a human ␥-herpesvirus that predominantly establishes latent infection in B lymphocytes
Introduction of point mutations into the ZII element of the viral genome did not increase the level of BZLF1 production, silencing of endogenous Jun dimerization protein 2 (JDP2) gene expression by RNA interference increased the levels of viral early gene products and viral DNA replication. These results indicate that JDP2 plays a role as a repressor of Zp and that its replacement by cyclic AMP-response element-binding protein (CREB)/ activating transcription factor (ATF)/activator protein-1 (AP-1) at ZII is crucial to triggering reactivation from latency to lytic replication
JDP2 Represses Transcription from EBV Zp—Because JDP2 represses transcriptional activation of reporter constructs containing cAMP-response element or tetradecanoylphorbol 13-acetate (TPA)-responsive elements [23], we hypothesized that JDP2 might regulate the BZLF1 transcription and thereby affect EBV reactivation
Summary
The Epstein-Barr virus (EBV)2 is a human ␥-herpesvirus that predominantly establishes latent infection in B lymphocytes. JDP2 binds to ZII, but not to the ZIIIA or ZIIIB cis-elements of Zp. Association of JDP2 with the BZLF1 Promoter in Vivo—To further verify the reporter assays and EMSA results, we performed ChIP analysis using cells containing wild-type or BZLF1 knock-out (BZLF1KO) EBV-BAC [27]. Because the above documented results indicated JDP2 acts to suppress the BZLF1 promoter by binding to the ZII cis-element, we generated recombinant EBV with a point mutation in the ZII element (Fig. 4A).
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