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An ATF/CRE element mediates both EBNA2-dependent and EBNA2-independent activation of the Epstein-Barr virus LMP1 gene promoter.

Artikel i vetenskaplig tidskrift
Författare A Sjöblom-Hallén
Weiwen Yang
Lars Palmqvist
Ann Jansson
Lars Rymo
Publicerad i Journal of virology
Volym 72
Nummer/häfte 2
Sidor 1365-76
ISSN 0022-538X
Publiceringsår 1998
Publicerad vid Institutionen för laboratoriemedicin, Avdelningen för klinisk kemi/transfusionsmedicin
Sidor 1365-76
Språk en
Länkar www.ncbi.nlm.nih.gov/entrez/query.f...
Ämnesord Activating Transcription Factor 1, Activating Transcription Factor 2, Cell Line, Cyclic AMP Response Element-Binding Protein, genetics, DNA-Binding Proteins, Epstein-Barr Virus Nuclear Antigens, genetics, Gene Expression Regulation, Viral, Herpesvirus 4, Human, genetics, Humans, Oncogene Proteins, Viral, genetics, Promoter Regions, Genetic, genetics, Transcription Factors, genetics, Viral Matrix Proteins, genetics
Ämneskategorier Medicinsk cellbiologi, Virologi, Tumörbiologi

Sammanfattning

The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) is a viral oncogene whose expression is regulated by both viral and cellular factors. EBV nuclear antigen 2 (EBNA2) is a potent transactivator of LMP1 expression in human B cells, and several EBNA2 response elements have been identified in the promoter regulatory sequence (LRS). We have previously shown that an activating transcription factor/cyclic AMP response element (ATF/CRE) site in LRS is involved in EBNA2 responsiveness. We now establish the importance of the ATF/CRE element by mutational analysis and show that both EBNA2-dependent activation and EBNA2-independent activation of the promoter occur via this site but are mediated by separate sets of factors. An electrophoretic mobility shift assay (EMSA) with specific antibodies showed that the ATF-1, CREB-1, ATF-2 and c-Jun factors bind to the site as ATF-1/CREB-1 and ATF-2/c-Jun heterodimers whereas the Sp1 and Sp3 factors bind to an adjacent Sp site. Overexpression of ATF-1 and CREB-1 in the cells by expression vectors demonstrated that homodimeric as well as heterodimeric forms of the factors transactivate the LMP1 promoter in an EBNA2-independent manner. The homodimers of ATF-2 and c-Jun did not significantly stimulate promoter activity. In contrast, the ATF-2/c-Jun heterodimer had only a minor stimulatory effect in the absence of EBNA2 but induced a strong transactivation of the LMP1 promoter when coexpressed with this protein. Evidence for a direct interaction between the ATF-2/c-Jun heterodimeric complex and EBNA2 was obtained by EMSA and coimmunoprecipitation experiments. Thus, our results suggest that EBNA2-induced transactivation via the ATF/CRE site occurs through a direct contact between EBNA2 and an ATF-2/c-Jun heterodimer. EBNA2-independent promoter activation via this site, on the other hand, is mediated by a heterodimeric complex between the ATF-1 and CREB-1 factors.

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