Human hepatitis B virus enhancer 1 is responsive to human interleukin-6.
Serum levels of interleukin-6 (IL-6) are elevated in acute and chronic hepatitis B patients. The effect of IL-6 and its transcription factor of NF-IL6 (a nuclear factor for IL-6) on hepatitis B virus (HBV) enhancer 1 (Enh1), which controls HBV X expression, were investigated in HepG2 cells. Twenty ng/ml of IL-6 increased 4-fold the enhancer activity of Enh1 according to the CAT assay. The IL-6 stimulation was abolished by introducing a mutation either in an AP-1-related site or a C-stretch sequence in the Enh1 sequence, demonstrating that the cis-elements are necessary for the IL-6 response. Co-transfection of NF-IL6 expression plasmid similarly increased the enhancer activity of Enh1 through both binding sites. Further, a specific complex formation of the Enh1 was detected using HepG2 nuclear lysates by electromobility shift assays, and the complex formation was increased in the lysates of cells treated with IL-6 and NF-IL6-transfection. In competition assays, one half of the complex formed was found to remain in the presence of 500-times excess competitor DNA fragment harboring NF-IL2 binding site, suggesting indirect binding of NF-IL6 to the Enh1 sequence. These results indicate that IL-6 increased the enhancer activity of HBV Enh1 through signal transduction pathways, indirectly involving NF-IL6, and may control HBV X expression and viral replication in HBV infected liver.
Ohno
H
H
First Department of Internal Medicine, Faculty of Medicine, Kanazawa University, Ishikawa, Japan.
Kaneko
S
S
Kobayashi
K
K
Murakami
S
S
D001483:Base Sequence; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000187:drug effects*; D017930:Genes, Reporter; D005814:Genes, Viral / Q000187:drug effects; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins; D014779:Virus Replication
D022762:CCAAT-Enhancer-Binding Proteins; C497252:CEBPD protein, human; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D051743:CCAAT-Enhancer-Binding Protein-delta; D015500:Chloramphenicol O-Acetyltransferase