title: A dominant negative mutant of an IFN regulatory factor family protein inhibits both type I and type II IFN-stimulated gene expression and antiproliferative activity of IFNs.
abstract: Type I (alpha,beta) and type II (gamma) IFNs elicit antiproliferative and antiviral activities through two distinct transcription pathways involving 1) IRF family proteins and ISGF3, and 2) STAT1. We have employed a dominant negative strategy to study the role of IRF family proteins in eliciting the biologic activities of IFN. A truncated IRF protein retaining the DNA-binding domain (DBD) of ICSBP (a member of the IRF family) was stably transfected into U937 monocytic cells. Clones expressing DBD had markedly reduced ISRE-binding activity and were defective in expressing several type I IFN-inducible genes. STAT1 was one such type I IFN-inducible gene whose expression was also inhibited in DBD clones. As a result, the expression of several IFN-gamma-inducible genes was also inhibited in these clones, indicating functional coupling of the type I and type II IFN transcription pathways. Furthermore, DBD clones grew more slowly than control clones and were refractory to antiproliferative effects of both types of IFNs. We found that IFN treatment of U937 cells leads to a G1 arrest and an increase in underphosphorylated retinoblastoma gene product. However, IFN treatment did not change the cell cycle profile, nor retinoblastoma gene product phosphorylation state in DBD clones. These data indicate that expression of DBD disrupts cell cycle regulatory mechanisms. Combined with the previously noted failure of DBD clones to elicit antiviral activity, the present work shows that IRF family proteins play an integral part in growth control activities of IFNs.
authors.affiliation: Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Thornton
authors.forename: V V
authors.initials: VV
authors.lastname: Ogryzko
authors.forename: A
authors.initials: A
authors.lastname: Dent
authors.forename: R
authors.initials: R
authors.lastname: Sharf
authors.forename: B Z
authors.initials: BZ
authors.lastname: Levi
authors.forename: Y
authors.initials: Y
authors.lastname: Kanno
authors.forename: L M
authors.initials: LM
authors.lastname: Staudt
authors.forename: B H
authors.initials: BH
authors.lastname: Howard
authors.forename: K
authors.initials: K
authors.lastname: Ozato
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002999:Clone Cells; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D050835:Interferon Regulatory Factors; D007370:Interferon Type I / Q000494:pharmacology*; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D007371:Interferon-gamma / Q000494:pharmacology*; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation; D011817:Rabbits; D012097:Repressor Proteins; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014162:Transfection; D000099185:Interferon Regulatory Factor-8
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D050835:Interferon Regulatory Factors; D007370:Interferon Type I; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D007371:Interferon-gamma; D010750:Phosphoproteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D050794:STAT1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D000099185:Interferon Regulatory Factor-8; C494257:IRF1 protein, human; C494229:IRF2 protein, human; C494227:IRF9 protein, human; C494079:STAT1 protein, human