Evidence for IRF-1-dependent gene expression deficiency in interferon unresponsive HepG2 cells.
Induction of the antiproliferative and antiviral state by IFNs (type I and II) is dramatically impaired in HepG2 cells. We show here that RNase L, IDO, GBP-2 and iNOS genes normally expressed as a secondary response to IFN are no longer inducible in HepG2 cells, while induction of primary response genes (IRF-1, PKR, p48-ISGF3gamma, 2-5AS, 6-16 and p56-(trp)tRNA) are unaffected. On the basis of previous data implicating transcription factor IRF-1 in the induction of some IFN-induced genes, we tested the effects of transfecting an IRF-1 oligonucleotide antisense in HeLa cells and found specifically impaired IFN induction of secondary response genes (RNase L, IDO and GBP-2). This raised the possibility that IRF-1 was defective in HepG2 cells. However, some molecular and biochemical analyses reveal that IRF-1 is induced normally by IFNs and retains its normal size, cellular location, phosphorylation status and ability to bind the IDO promoter in vitro. Therefore, we conclude that although the primary response pathway is fully functional, some aspects of the secondary pathway involving IRF-1 (but not IRF-1 itself) are defective in HepG2 cells. It may be possible that the promoter region of these deficient HepG2-genes requires an unidentified transcription factor in addition to de novo IRF-1, which could be elicited by a cooperative activator.
Tnani
M
M
UMR 5539 Centre National de la Recherche Scientifique, Université de Montpellier II, Place E. Bataillon, Case 107, 34095, Montpellier Cédex 5, France.
Bayard
B A
BA
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004686:Encephalomyocarditis virus / Q000187:drug effects; D004722:Endoribonucleases / Q000096:biosynthesis; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins; D005786:Gene Expression Regulation / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D050856:Interferon Regulatory Factor-1; D007372:Interferons / Q000494:pharmacology*; D051379:Mice; D016376:Oligonucleotides, Antisense / Q000235:genetics; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics*; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014366:Tryptophan Oxygenase / Q000096:biosynthesis; D014407:Tumor Cells, Cultured; D014721:Vesicular stomatitis Indiana virus / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects
D004268:DNA-Binding Proteins; C490287:GBP1 protein, human; C490288:Gbp2b protein, mouse; C494257:IRF1 protein, human; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; D012333:RNA, Messenger; D007372:Interferons; D014366:Tryptophan Oxygenase; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease; D019204:GTP-Binding Proteins