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Journal of Virology, November 2001, p. 10334-10347, Vol. 75, No. 21
The Wistar Institute, Philadelphia,
Pennsylvania 19104,1 and University
of Birmingham, Birmingham, United Kingdom2
Received 16 April 2001/Accepted 17 July 2001
Epstein-Barr virus (EBV) lytic cycle transcription and
DNA replication require the transcriptional activation function of the
viral immediate-early protein Zta. We describe a series of alanine
substitution mutations in the Zta activation domain that reveal two
functional motifs based on amino acid composition. Alanine
substitution of single or paired hydrophobic aromatic amino acid
residues resulted in modest transcription activation defects,
while combining four substitutions of aromatic residues (F22/F26/W74/F75) led to more severe transcription defects.
Substitution of acidic amino acid residue E27, D35, or E54 caused
severe transcription defects on most viral promoters.
Promoter- and cell-specific defects were observed for some substitution
mutants. Aromatic residues were required for Zta interaction with
TFIIA-TFIID and the CREB-binding protein (CBP) and for stimulation of
CBP histone acetyltransferase activity in vitro. In contrast, acidic
amino acid substitution mutants interacted with TFIIA-TFIID and CBP
indistinguishably from the wild type. The nuclear domain 10 (ND10)
protein SP100 was dispersed by most Zta mutants, but acidic residue
mutations led to reduced, while aromatic substitution mutants led to
increased SP100 nuclear staining. Acidic residue substitution
mutants had more pronounced defects in transcription activation of
endogenous viral genes in latently infected cells and for viral
replication, as measured by the production of infectious virus. One
mutant, K12/F13, was incapable of stimulating EBV lytic replication but had only modest transcription defects. These results indicate that Zta
stimulates viral reactivation through two nonredundant structural
motifs, one of which interacts with general transcription factors and
coactivators, and the other has an essential but as yet not
understood function in lytic transcription.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.21.10334-10347.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification of Acidic and Aromatic Residues in the
Zta Activation Domain Essential for Epstein-Barr Virus
Reactivation
*
Corresponding author. Mailing address: The Wistar
Institute, Philadelphia, PA 19104. Phone: (215) 898-9491. Fax:
(215) 898-0663. E-mail: lieberman{at}wistar.upenn.edu.
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