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PMID: 2347309 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't

The X protein of the hepatitis B virus acts as a transcription factor when targeted to its responsive element.

The EMBO journal ·Vol. 9 ·No. 6 ·1990-06-00 ·Pages 1889-95

Unger T, Shaul Y

Abstract

The X protein of hepatitis B virus (HBV) stimulates transcription of a large number of viral enhancers. This protein augments the activity of the HBV enhancer through a specific cis element, termed X responsive element (XRE). Multimers of XRE exhibit enhancer activity which is further stimulated by X. XRE binds multiple cellular transcription factors one of which is the C/EBP. We have constructed the DB gene containing the DNA-binding domain of the C/EBP. This gene efficiently represses the enhancer activity of the XRE by competitive displacement of the XRE-binding factors. Under these conditions, X was found to have only a partially stimulatory effect on transcription, suggesting that the XRE-binding proteins are required for the activity of X. In contrast, an X-DB hybrid protein that binds to the XRE is a strong transcription factor and acts without additional XRE-binding proteins. Furthermore, studies of X mutants revealed that the carboxy-terminus of the protein is required for this activation. These data show that X directly stimulates the cellular transcription machinery, possibly by protein-protein interaction with the XRE-binding factors.

MeSH Terms
Amino Acid Sequence Base Sequence Chimera DNA, Viral/metabolism Genes, Viral Hepatitis B virus/genetics Molecular Sequence Data Retroviridae Proteins/genetics Trans-Activators/genetics Transcription Factors/genetics Transcription, Genetic Transcriptional Activation Viral Regulatory and Accessory Proteins
Chemicals
DNA, Viral Retroviridae Proteins Trans-Activators Transcription Factors Viral Regulatory and Accessory Proteins hepatitis B virus X protein
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
Unger T
Department of Molecular Genetics and Virology, Weizmann Institute of Science, Rehovot, Israel.
Shaul Y
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Article Info
Journal
The EMBO journal
Abbr.
EMBO J
ISSN
0261-4189
Published
1990-06-00
Pages
1889-95
Language
English
Region
England
NLM ID
8208664
PMCID
PMC551895
Subset
IM
External Links
PubMed source PMC Full Text View journal details
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