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J. Virol., Jun 1996, 3844-3851, Vol 70, No. 6
M Bondesson, K Ohman, M Manervik, S Fan and G Akusjarvi
Here we show that the adenovirus early region 4 (E4) open reading frame 4
(ORF4) protein autoregulates its own transcription by inhibiting adenovirus
E1A-induced activation of E4 transcription both in transient transfection
experiments and during lytic virus growth. The inhibitory activity of
E4-ORF4 was selective for E1A-CR3-dependent transactivation and had no
effect on CR1 transactivation. The inhibitory activity of E4- ORF4 was
relieved by okadaic acid treatment, which inhibits the cellular protein
phosphatase 2A (PP2A), suggesting that E4-ORF4 controls the phosphorylated
status of transcription factors important for E4 promoter activity. This
conclusion agrees with previous demonstrations that E4-ORF4 associates with
PP2A and causes a partial dephosphorylation of certain transcription
factors, including E1A (U. Muller, T. Kleinberger, and T. Shenk, J. Virol.
66:5869-5878, 1992; T. Kleinberger and T. Shenk, J. Virol. 67:7556-7560,
1993). However, our results indicate that dephosphorylation of E1A itself
might not be the primary target for E4-ORF4. Instead, the E4-ORF4-PP2A
complex appears to work by dephosphorylation of multiple cellular
transcription factors that are involved in E1A transactivation of the E4
promoter.
Copyright © 1996, American Society for Microbiology
Adenovirus E4 open reading frame 4 protein autoregulates E4 transcription by inhibiting E1A transactivation of the E4 promoter
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, Stockholm, Sweden.
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