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Mol. Cell. Biol., Oct 1997, 5748-5757, Vol 17, No. 10
L Zhang and JS Pagano
The Epstein-Barr virus (EBV) BamHI Q promoter (Qp) is the only promoter
used for the transcription of Epstein-Barr virus nuclear antigen 1 (EBNA-1)
mRNA in cells in the most restricted (type I) latent infection state.
However, Qp is inactive in type III latency. With the use of the yeast
one-hybrid system, a new cellular gene has been identified that encodes
proteins which bind to sequence in Qp. The deduced amino acid sequence of
the gene has significant homology to the interferon regulatory factors
(IRFs). This new gene and products including two splicing variants are
designated IRF-7A, IRF-7B, and IRF-7C. The expression of IRF-7 is
predominantly in spleen, thymus, and peripheral blood leukocytes (PBL).
IRF-7 proteins were identified in primary PBL with specific antiserum
against IRF-7B protein. IRF-7s can bind to interferon-stimulated response
element (ISRE) sequence and repress transcriptional activation by both
interferon and IRF-1. Additionally, a functional viral ISRE sequence,
5'-GCGAAAACGAAAGT-3', has been identified in Qp. Finally, the expression of
IRF-7 is consistently high in type III latency cells and almost
undetectable in type I latency, corresponding to the activity of endogenous
Qp in these latency states and the ability of the IRF-7 proteins to repress
Qp-reporter constructs. The identification of a functional viral ISRE and
association of IRF-7 with type III latency may be relevant to the mechanism
of regulation of Qp.
Copyright © 1997, American Society for Microbiology
IRF-7, a new interferon regulatory factor associated with Epstein-Barr virus latency
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599-7295, USA. luzhang@med.unc.edu
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