Regulation of hepatitis B virus core promoter by transcription factors HNF1 and HNF4 and the viral X protein.
Hepatitis B virus (HBV) core promoter contains a binding site for nuclear receptors. A natural double mutation in this binding site, which changes nucleotide (nt) 1765 from A to T and nt 1767 from G to A, selectively abolishes the binding of several nuclear receptors without affecting that of HNF4. This double mutation also creates a binding site for the transcription factor HNF1 and changes two amino acids in the overlapping X protein sequence. In this study, we have examined the roles of HNF1, HNF4, and the X protein in the regulation of the core promoter activities in Huh7 hepatoma cells. Our results indicate that HNF4 could stimulate the expression of the precore RNA and the core RNA from the core promoter of both the wild-type (WT) HBV and the double mutant, although its effect on the former was more prominent. In contrast, HNF1, which did not affect the WT core promoter, suppressed the precore RNA expression of the double mutant. Further analysis using HBV genomic constructs, with and without the ability to express the X protein, indicates that the X protein did not affect the HNF4 activity on the core promoter and affected the HNF1 activity on the core promoter of only the double mutant. Thus, our results indicate that the phenotypic differences of HBV WT and double-mutant core promoters are at least partially due to the differential activities of HNF1, HNF4, and the X protein on these two promoters.
Zheng
Yanyan
Y
Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, CA 90033, USA.
Li
Jie
J
Ou
Jing-hsiung
JH
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006512:Hepatitis B Core Antigens / Q000235:genetics / Q000378:metabolism*; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; D006512:Hepatitis B Core Antigens; D051538:Hepatocyte Nuclear Factor 1-alpha; D051557:Hepatocyte Nuclear Factor 4; D009687:Nuclear Proteins; D010750:Phosphoproteins; D015534:Trans-Activators; D014157:Transcription Factors; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D051537:Hepatocyte Nuclear Factor 1