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J. Virol., 01 1995, 253-262, Vol 69, No. 1
E Johannsen, E Koh, G Mosialos, X Tong, E Kieff and SR Grossman
Expression of the Epstein-Barr virus (EBV) latent membrane protein 1
(LMP-1) oncogene is regulated by the EBV nuclear protein 2 (EBNA-2)
transactivator. EBNA-2 is known to interact with the cellular DNA- binding
protein J kappa and is recruited to promoters containing the GTGGGAA J
kappa recognition sequence. The minimal EBNA-2-responsive LMP- 1 promoter
includes one J kappa-binding site, and we now show that mutation of that
site, such that J kappa cannot bind, reduces EBNA-2 responsiveness by 60%.
To identify other factors which interact with the LMP-1 EBNA-2 response
element (E2RE), a -236/-145 minimal E2RE was used as a probe in an
electrophoretic mobility shift assay. The previously characterized factors
J kappa, PU.1, and AML1 bind to the LMP-1 E2RE, along with six other
unidentified factors (LBF2 to LBF7). Binding sites were mapped for each
factor. LBF4 is B- and T-cell specific and recognizes the PU.1 GGAA core
sequence as shown by methylation interference. LBF4 has a molecular mass of
105 kDa and is probably unrelated to PU.1. LBF2 was found only in
epithelial cell lines, whereas LBF3, LBF5, LBF6, and LBF7 were not cell
type specific. Mutations of the AML1- or LBF4-binding sites had no effect
on EBNA-2 transactivation, whereas mutation of the PU.1-binding site
completely eliminated EBNA-2 responses. A gst-EBNA-2 fusion protein
specifically depleted PU.1 from nuclear extracts and bound in vitro
translated PU.1, providing biochemical evidence for a direct EBNA-2-PU.1
interaction. Thus, EBNA-2 transactivation of the LMP-1 promoter is
dependent on interaction with at least two distinct sequence-specific
DNA-binding proteins, J kappa and PU.1. LBF3, LBF5, LBF6, or LBF7 may also
be involved, since their binding sites also contribute to EBNA-2
responsiveness.
Copyright © 1995, American Society for Microbiology
Epstein-Barr virus nuclear protein 2 transactivation of the latent membrane protein 1 promoter is mediated by J kappa and PU.1
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts.
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