title: Characterization of TH3, an induction-specific protein interacting with the interferon beta promoter.
abstract: We report the purification and characterization of a unique DNA-binding protein termed TH3 that interacts with the positive regulatory domain (PRD) I and PRDIII domains of the interferon (IFN) beta promoter. In cells treated with poly rl:rC and cycloheximide, appearance of TH3 DNA-binding activity was inversely proportional to the disappearance of a constitutive complex TH1 and coincided temporally with induction of IFN-beta gene transcription. The TH3 DNA-binding protein is a small 14-kDa polypeptide that appears to be derived from the TH1 complex; TH1 in turn is related to interferon regulatory factor (IRF) 2 by immunological cross-reactivity. The TH3 protein appeared to lack the epitope required for recognition by anti-IRF-2 antisera; however, a short microsequence obtained for TH3 overlapped a sequence from the IRF-2 protein. Although TH3 binds to multimers of the AAGTGA hexamer and to PRDI, the TH3 protein alone had a predominantly neutral phenotype on PRDI-dependent transcription in vitro and lacked the negative transcriptional effect attributed to IRF-2. These results raise the possibility that specific proteolysis of a negative regulatory protein involved in silencing the IFN-beta promoter may be an important event leading to transcriptional activation of the interferon gene.
authors.affiliation: Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Quebec.
authors.forename: L
authors.initials: L
authors.lastname: Cohen
authors.forename: J
authors.initials: J
authors.lastname: Hiscott
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000302:isolation & purification*; D006367:HeLa Cells; D006801:Humans; D007369:Interferon Inducers / Q000302:isolation & purification / Q000378:metabolism*; D016899:Interferon-beta / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D007369:Interferon Inducers; C078422:TH3 protein; D014157:Transcription Factors; D016899:Interferon-beta; D003513:Cycloheximide