Characterization of nuclear proteins which bind to interferon-inducible transcriptional enhancers in hematopoietic cells

Nuclear proteins isolated from untreated lymphoid cells formed complexes with the interferon-inducible transcriptional enhancer (IITE) containing a 73- and an 84-kDa protein, whereas the nuclear proteins of untreated myeloid cells formed complexes with the IITE which contained 50-, 65-, and 73-, but not 84-kDa nuclear proteins. The difference in the molecular masses of the nuclear proteins binding to the IITE in lymphoid and myeloid cells was due to a phosphatase present in the cytoplasm of the myeloid cells. Induction of transcriptional activation by interferon was accompanied by the binding of a 95-kDa nuclear protein to the IITE 1-4 h after the start of exposure to interferon. Cycloheximide did not inhibit the binding of the 95-kDa nuclear protein or the transcriptional activation of α-interferon-inducible genes. These data suggest that the induction of gene transcription by α-interferon in hematopoietic cells may be associated with post-translational changes in a 95-kDa nuclear protein that binds to IITE, thereby leading to transcriptional activation. * This research was supported in part by National Cancer Institute, National Institutes of Health, Grant PO1 CA49639-01A1, American Cancer Society Grant IM-580, the Kleberg Foundation, the Sid Richardson Foundation, and the Gillson-Longenbaugh Foundation (to A. D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.