title: Regulation of Stat1 protein expression by phenylalanine 172 in the coiled-coil domain.
abstract: Stat1 plays an essential role in signal transduction and gene expression of various cytokines including interferons (IFNs). Although the mechanism of cytokine-induced activation of Stat1 and transcriptional regulation of Stat1 gene expression have been established, post-transcriptional regulation of Stat1 protein expression is not fully understood. Here, we report identification of a mutant of Stat1 that has decreased expression levels by using inducible translocation trap (ITT), a reporter gene-based detection system of nuclear translocation. The substitution of serine for phenylalanine 172 (F172S) in the coiled-coil domain causes marked decrease in Stat1 protein expression in various cell lines without decreasing its mRNA levels. Our results suggest that the decrease is caused by translational/post-translational mechanisms independent of proteasome machinery. These results suggest a novel potential mechanism of determination of specificity of Stat proteins and showed that the ITT system is a powerful technique to identify mutants of nuclear translocating signal transducers.
authors.affiliation: Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Akemi
authors.initials: A
authors.lastname: Hoshino
authors.forename: Shella
authors.initials: S
authors.lastname: Saint Fleur
authors.forename: Hodaka
authors.initials: H
authors.lastname: Fujii
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010649:Phenylalanine / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D014176:Protein Biosynthesis / Q000235:genetics; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D050794:STAT1 Transcription Factor / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D061988:Proteasome Inhibitors; D050794:STAT1 Transcription Factor; D010649:Phenylalanine; D007371:Interferon-gamma; D046988:Proteasome Endopeptidase Complex