Interferon-alpha stimulation of liver cells enhances hepatitis delta virus RNA editing in early infection.
OBJECTIVE
RNA editing controls the formation of hepatitis-delta-antigen-S and -L and therefore plays a central role in the hepatitis-delta-virus (HDV) life-cycle. Editing is catalyzed by the enzyme Adenosine-deaminase-acting-on-RNA1 (ADAR1) of which two different forms, ADAR1-L and ADAR1-S, exist. As ADAR1-L is induced by interferon (IFN)-alpha, we examined the influence of IFN-alpha-stimulation of host cells on HDV-RNA editing.


METHODS
Editing was studied in Huh-7-cells transfected with HDV-RNA on days 7, 14, 21 and 28 after transfection. ADAR1-L mRNA was measured by RT-PCR.


RESULTS
IFN-alpha-treatment led to a 5-fold higher expression of ADAR1-L and to an increase in editing from 14+/-2% (SD) in unstimulated controls to 27+/-4% (SD) on day 7 after transfection. Editing further increases over time to the same maximum level of 35% in IFN-alpha-treated as well as untreated cells.


CONCLUSIONS
By IFN-alpha-stimulation both ADAR1-L expression and editing are increased in Huh-7-cells at day 7, and the maximum level of edited antigenomes is reached earlier with IFN-alpha-treatment as compared to untreated cells. Thus, ADAR1-L appears to be able to increase editing, but the HDV genome apparently has an intrinsic negative feed-back regulation mechanism that limits editing to roughly a third of the genomes.
Institute of Immunology and Transfusion Medicine, University of Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany. dirkhartwig@gmx.de
Dirk
D
Hartwig
Lutz
L
Schoeneich
Jobst
J
Greeve
Claudia
C
Schütte
Isabel
I
Dorn
Holger
H
Kirchner
Holger
H
Hennig
D000243:Adenosine Deaminase / Q000096:biosynthesis / Q000235:genetics; D000998:Antiviral Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004279:DNA, Viral; D003699:Hepatitis D / Q000821:virology*; D003698:Hepatitis Delta Virus / Q000235:genetics*; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000821:virology*; D017393:RNA Editing / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins; D013997:Time Factors; D014162:Transfection
D000998:Antiviral Agents; D004279:DNA, Viral; D016898:Interferon-alpha; D007527:Isoenzymes; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase