Double-stranded RNA-induced interferon regulatory factor-1 gene expressionin FRTL-5 rat thyroid cells

Double-stranded RNA (dsRNA) plays a role in the regulation of cell growth a nd apoptosis as well as in the cellular antiviral responses. However. it re mains unknown if dsRNA-activated signaling systems are functional in the th yroid. Here we report the presence of the dsRNA-dependent protein kinase (P KR) in FRTL-5 rat thyroid cells. In poly(I)-poly(C) (pIC)-stimulated cells, activation of nuclear factor-kappaB (NF kappaB) binding was clearly induce d. Incubation of FRTL-5 cells with pIC resulted in a marked increase in int erferon regulatory factor-1 (IRF-1) mRNA and phosphorylated signal transduc er and activator of transcription-1 (STAT1) levels. Addition of pIC to cell s led to type I interferon (IFN) gene expression, especially IFN beta, whic h can induce STAT1 phosphorylation. suggesting that dsRNA indirectly induce d STAT1 phosphorylation through expression of type I IFN. Thus, our results suggest that the dsRNA-activated signaling pathway may be involved in the regulation of IFN-inducible genes in the thyroid. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.