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Mol. Cell. Biol., 08 1996, 4052-4063, Vol 16, No. 8
ML Schmitz, A Indorf, FP Limbourg, H Stadtler, EB Traenckner and PA Baeuerle
The genomes of human adenoviruses encode several regulatory proteins,
including the two differentially spliced gene products E1A and E1B. Here,
we show that the 13S but not the 12S splice variant of E1A of adenovirus
type 5 can activate the human transcription factor NF-kappaB in a bimodal
fashion. One mode is the activation of NF-kappaB containing the p65 subunit
from the cytoplasmic NF-kappaB-IkappaB complex. This activation required
reactive oxygen intermediates and the phosphorylation of IkappaBalpha at
serines 32 and 36, followed by IkappaBalpha degradation and the nuclear
uptake of NF-kappaB. In addition, 13S E1A stimulated the transcriptional
activity of the C- terminal 80 amino acids of p65 at a core promoter with
either a TATA box or an initiator (INR) element. The C-terminal 80 amino
acids of p65 were found to associate with E1A in vitro. The activation of
NF-kappaB- dependent reporter gene transcription by E1A was potently
suppressed upon coexpression of the E1B 19-kDa protein (19K). E1B 19K
prevented both the activation of NF-kappaB and the E1A-mediated
transcriptional enhancement of p65. These inhibitory effects were not found
for the 55- kDa splice variant of the E1B protein. We suggest that the
inductive effect of E1A 13S on the host factor NF-kappaB, whose activation
is important for the transcription of various adenovirus genes, must be
counteracted by the suppressive effect of E1B 19K so that the
adenovirus-infected cell can escape the immune-stimulatory and apoptotic
effects of NF-kappaB.
Copyright © 1996, American Society for Microbiology
The dual effect of adenovirus type 5 E1A 13S protein on NF-kappaB activation is antagonized by E1B 19K
Institute of Biochemistry and Molecular Biology, Albert-Ludwigs- Universitat, Freiburg, Germany.
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