Transcriptional Induction by Double-stranded RNA Is Mediated by Interferon-stimulated Response Elements without Activation of Interferon-stimulated Gene Factor 3

Abstract

Many genes induced by type I interferons (IFNs) are also induced by double-stranded (ds)RAN. In this study, we investigated the mechanism of this induction process. Using cell lines from which the type I IFN genes have been deleted, we established that induction by dsRNA of the IFN-inducible 561 gene is direct and not mediated by the intermediate synthesis of IFN. Unlike 561 mRNA, the IFN-inducible 6-16 mRNA was induced poorly by dsRNA. Transfection studies demonstrated that the sequence difference between the core IFN-stimulated response elements (ISREs) of these two genes is not responsible for their differential inducibility by dsRNA. A point mutation in the 561 ISRE that abolished its response to IFN-alpha also made it unresponsive to dsRNA, thus demonstrating that the ISRE is the relevant cis-acting element for dsRNA signaling. The roles of different known ISRE-binding protein and tyrosine kinases in transducing the signal elicited by dsRNA were evaluated in genetically altered cell lines. dsRNA failed to induce 561 mRNA in cells expressing an anti-sense RNA for interferon regulatory factor 1, whereas it was induced strongly in cells expressing the corresponding sense mRNA. 561 mRNA was also induced strongly by dsRNA, but not by IFN-alpha, in mutant cell lines that do not express functional tyrosine kinases Tyk2 or JAK1 or ISRE binding protein, p48, or STAT2, all of which are required for IFN-alpha signaling. However, in cells devoid of functional STAT1, which is also required for IFN-alpha signaling, the induction of 561 mRNA by dsRNA was very low. Expression of transfected STAT1 alpha protein, but not of STAT 1beta protein, in these cells greatly enhanced the dsRNA inducibility of the 561 gene. These studies indicated that the major ISRE-mediated signaling pathway used by dsRNA requires interferon regulatory factor 1 and STAT alpha. This pathway, however, does not require the other known cytoplasmic components used for IFN-alpha signaling.

Identification and expression analysis of two IFN-inducible genes in crucian carp (Carassius auratus L.)

“…IFI56 is the most strongly induced gene among all ISGs (Der et al, 1998) and displays diverse activated pathway by different stimuli (Guo et al, 2000b;Peters et al, 2002;Grandvaux et al, 2002). In response to dsRNA stimulation, human IFI56 is sufficient to be induced rapidly by activation of cellular latent IRF3 without ongoing protein synthesis (Bandyopadhyay et al, 1995;Peters et al, 2002). Similar results have obtained for human IFI54 and IFI60 (Grandvaux et al, 2002).…”

“…It can be rapidly induced to a high level in IFN-treated cell (Bandyopadhyay et al, 1995). Indeed, human IFI56 mRNA was noted to be the most abundant IFN-induced mRNA in a gene array analysis (Der et al, 1998).…”

p38-dependent Activation of Interferon Regulatory Factor 3 by Lipopolysaccharide

“…The LPS-induced ISG was not accompanied by formation of the ISGF3 complex, nor did we detect any tyrosine phosphorylation of STAT proteins involved in ISG induction (data not shown). Furthermore, LPS induction of ISG54 was also observed in GRE cells 2 which carry a deletion of the type I interferon locus (25). Thus, it is reasonable to assume that the observed ISG induction is indeed mediated through the activation of IRF3.…”

Hyaluronan-Mediated Leukocyte Adhesion and Dextran Sulfate Sodium-Induced Colitis Are Attenuated in the Absence of Signal Transducer and Activator of Transcription 1

“…33 Many reports have demonstrated the activation of STAT1 by cytokines and growth factors. 10 -13,16 Because STAT1 is important for poly I:C-stimulated IFN-inducible gene induction, 33 we investigated whether poly I:C activates STAT1 in primary human colon M-SMCs. Cultures of human M-SMCs were treated with or without poly I:C for 0, 2, and 4 hours, and STAT-DNA binding activity was measured by gelshift assay.…”