Activating Transcription Factor 2 (ATF2) Down-regulates Hepatitis B Virus X Promoter Activity by the Competition for the Activating Protein 1 Binding Site and the Formation of the ATF2-Jun Heterodimer

The hepatitis B viral X promoter is known to be positively autoregulated by its own HBx protein, which also interacts with many cellular regulatory proteins. We investigated the effect of activating transcription factor 2 (ATF2) on the activity of the X promoter. Cotransfection of the ATF2 expressio...

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Bibliographic Details
Published in:The Journal of biological chemistry 1997-07, Vol.272 (27), p.16934-16939
Main Authors: Choi, Cheol Yong, Choi, Byung Hyune, Park, Geon Tae, Rho, Hyune Mo
Format: Article
Language:English
Subjects:
Activating Transcription Factor 2
Binding Sites
Binding, Competitive
Chloramphenicol O-Acetyltransferase - genetics
Cyclic AMP Response Element-Binding Protein - metabolism
Dimerization
Down-Regulation
Enhancer Elements, Genetic - genetics
hepatitis B virus
Hepatitis B virus - genetics
Humans
Leucine Zippers
Promoter Regions, Genetic
Proto-Oncogene Proteins c-jun - metabolism
Transcription Factors - metabolism
Tumor Cells, Cultured
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Summary:The hepatitis B viral X promoter is known to be positively autoregulated by its own HBx protein, which also interacts with many cellular regulatory proteins. We investigated the effect of activating transcription factor 2 (ATF2) on the activity of the X promoter. Cotransfection of the ATF2 expression vector with a X promoter-chloramphenicol acetyltransferase plasmid repressed the X promoter activity in HepG2 cells. HBx activated activating protein 1 (AP-1)-mediated transcription through the hepatitis B virus E element by 35-fold, while its activation activity was inhibited in the presence of ATF2, suggesting that ATF2 inhibited the autoactivation of X promoter by HBx and basal transcription mediated by AP-1. Since the binding sites of AP-1 and ATF2 in the hepatitis B virus E element overlap, the repression of X promoter activity by ATF2 is exerted by the competition for the AP-1 binding site and the formation of the ATF2-Jun heterodimer as in the case of the consensus AP-1 element. However, the small X promoter had a ATF2 binding site and was activated by ATF2. These results suggest that the syntheses of X proteins are differentially regulated by ATF2.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.272.27.16934