PU box-binding transcription factors and a POU domain protein cooperate in the Epstein--Barr virus (EBV) nuclear antigen 2-induced transactivation of the EBV latent membrane protein 1 promoter

Abstract

Expression of the Epstein-Ban" virus (EBV) latent membrane protein (LMP1) is regulated by virus-and host cell-specific factors. The EBV nuclear antigen 2 (EBNA2) has been shown to transactivate a number of viral and cellular gene promoters including the promoter for the LMP1 gene. EBNA2 is targeted to at least some of these promoters by interacting with a cellular DNA binding protein, RBP-Jlc. In the present report we confirm and extend our previous observation that the LMP1 promoter can be activated by EBNA2 in the absence of the RBP-Jtc-binding sequence in the LMP1 promoter regulatory region (LRS). We show that two distinct LRS regions, -106 to +40 and -176 to -136, contribute to EBNA2 responsiveness. Site-directed mutagenesis analysis of the upstream -176/-136 EBNA2 responsive element revealed that two critical cis-acting elements are required for full promoter function. These same elements analysed by electrophoretic mobility shift assays define two binding sites recognized by nuclear factors derived from B cells. An octamer-like sequence (-147 to -139) contained overlapping binding sites for an unidentified transcriptional repressor on the one hand and a factor(s) belonging to the POU domain family but distinct from Oct-1 and Oct-2 on the other. An adjacent purine tract (-171 to -155) held a PU.1 binding site, which was also recognized by a related factor. The results suggest that the POU domain protein and either of two PU boxbinding factors bind simultaneously to LRS, creating a ternary complex that might be in part responsible for mediating the transactivation of the LMP1 promoter by EBNA2. There were no qualitative differences between EBV-negative and EBV-positive cells with regard to transcription factor binding to the octamer-like sequence and the PU.1 recognition site, as revealed by electrophoretic mobility shift assays.

Cellular Corepressor TLE2 Inhibits Replication-and-Transcription- Activator-Mediated Transactivation and Lytic Reactivation of Kaposi's Sarcoma-Associated Herpesvirus

“…Downregulation of RTA-mediated transactivation by TLE2 could be an important mechanism by which the host cell responds to the microenvironmental stimuli that potentially reactivate the virus through preventing expression of viral genes and suppressing viral DNA replication during coevolution of virus and host. This is supported by recent studies on EpsteinBarr virus, another human herpesvirus, which have demonstrated that the corepressor Groucho/TLE can repress EBNA1 (Epstein-Barr virus nuclear antigen 1) auto-activation and interfere with latent infection by cooperation with Oct-1 (60).…”

Regulation of Expression of the Epstein-Barr Virus BamHI-A Rightward Transcripts

“…Having two control regions also allows tissue-specific or signal transduction-specific expression after establishment of infection. LMP1 is also expressed from two promoters that are responsive to completely different transcription factors (6,9,23,35,46,50,51,59).…”

Protein Kinase A Associates with HA95 and Affects Transcriptional Coactivation by Epstein-Barr Virus Nuclear Proteins

“…EBNA-2 activates transcription of cellular genes, including CD21, CD23, and c-myc and of viral genes, including the EBNAs, LMP1, and LMP2 (1,2,8,17,32,60,(69)(70)(71). EBNA-2 has the intrinsic ability to self associate and recognizes promoters by binding to RBP-J and PU.1/Spi1, cellular transcription factors that recognize specific DNA sequences (20,25,26,31,58). Once associated with a promoter, the EBNA-2 acidic domain can recruit basal and activated transcription factors p300, CBP, and PCAF histone acetylases and a p100 transcriptional coactivator (25,(65)(66)(67)73).…”