Abstract
The X gene of human hepatitis B virus encodes the polypeptide HBx which transactivates viral and host genes through a variety of cis-acting enhancer elements present in RNA polymerases I, II and III promoters. To better understand the mechanism of X transactivation, we cloned cDNAs of proteins that bind HBx. Here we demonstrate that one of these cDNAs is a full-length cDNA of human RPB5, a subunit shared by RNA polymerases. The HBx transactivation domain and the central region of human RPB5 were necessary for the specific binding of the two proteins as shown by: (i) in vitro assays using deletion mutants of fusion proteins; (ii) in vivo assays which detect associated proteins by co-immunoprecipitation of the non-fused proteins from transfected HepG2 cells. Over-expressed HBx seemed to associate with assembled forms of endogenous human RPB5 in HBx-transfected cells, since the endogenous RPB5 co-immunoprecipitated with HBx. The HBx binding region of human RPB5 by itself stimulated chloramphenicol acetyltransferase activities from several different reporters having X-responsive element(s). Our results support the idea that the interaction of HBx and human RPB5 can facilitate HBx transactivation and that human RPB5 has a domain which can communicate with transcriptional regulators.
Original language | English (US) |
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Pages (from-to) | 143-150 |
Number of pages | 8 |
Journal | EMBO Journal |
Volume | 14 |
Issue number | 1 |
DOIs | |
State | Published - 1995 |
Externally published | Yes |
Keywords
- HBV X protein
- Human RPB5
- RNA polymerases
- Transactivation
- X-associated protein
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology