Immunosuppressive function of hepatitis B antigens in vitro: role of endoribonuclease V as one potential trans inactivator for cytokines in macrophages and human hepatoma cells.
The mRNAs of transiently expressed cytokine genes contain AUUUA-rich sequences in the 3' untranslated regions. In order to examine whether the AU-specific endoribonuclease V (EC 3.1.27.8) described previously by us transinactivates those mRNA species, we introduced a 51-nucleotide ATTTA sequence from tumor necrosis factor into the 3' untranslated region of beta-globin gene. Transcripts of that construct, synthesized in vitro, were prone to endoribonuclease V digestion at those AU-rich sequences. Stimulation of human macrophages with lipopolysaccharide resulted in a shift of the association state of the enzyme from the nuclear matrix-associated to the free form. This shift was strongly prevented by the hepatitis B surface antigen (HBsAg) and more weakly by hepatitis B nucleocapsid antigen and hepatitis B antigen of the X region. HBsAg and, to a lesser extent, hepatitis B nucleocapsid antigen and hepatitis B antigen of the X region inhibited the release of alpha interferon, tumor necrosis factor alpha, and granulocyte-macrophage colony stimulating factor, while it had no effect on interleukin-1 production from stimulated macrophages. Using the human hepatoma cell line PLC/PRF/5, we provide further experimental evidence that endoribonuclease V acts in trans as a posttranscriptional inactivator for nuclear matrix-associated cytokine transcripts. These results suggest that those cytokine transcripts which contain reiterated (overlapping) AUUUA sequences are degraded by nuclear matrix-associated endoribonuclease V. This degradation was comparably high in cells incubated with HBsAg or cells which produced this antigen.
Jochum
C
C
Abteilung Angewandte Molekularbiologie, Institut für Physiologische Chemie, Duesbergweg, Federal Republic of Germany.
Voth
R
R
Rossol
S
S
Meyer zum Büschenfelde
K H
KH
Hess
G
G
Will
H
H
Schröder
H C
HC
Steffen
R
R
Müller
W E
WE
D000818:Animals; D001483:Base Sequence; D001685:Biological Factors / Q000235:genetics*; D006528:Carcinoma, Hepatocellular; D002417:Cattle; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines; D004722:Endoribonucleases / Q000378:metabolism*; D005784:Gene Amplification; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics; D006514:Hepatitis B Surface Antigens / Q000276:immunology*; D006801:Humans; D007165:Immunosuppression Therapy; D008070:Lipopolysaccharides / Q000494:pharmacology; D008113:Liver Neoplasms; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D010957:Plasmids; D013379:Substrate Specificity; D013950:Thymus Gland / Q000201:enzymology; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D001685:Biological Factors; D016207:Cytokines; D006514:Hepatitis B Surface Antigens; D008070:Lipopolysaccharides; D015345:Oligonucleotide Probes; D005914:Globins; D004722:Endoribonucleases; C025115:ribonuclease V