c-fos mRNA Expression in Macrophages Is Downregulated by Interferon-γ at the Posttranscriptional Level

Abstract

Treatment of macrophages with interferon-7 (IFN7) strongly decreased the induction of c-fos mRNA by 12-O-tetradecanoylphorbol-13-acetate (TPA), lipopolysaccharide, or calcium ionophore A23187 in macrophages. Under the same experimental conditions, IFN7 induced oligo(A) synthetase mRNA and did not affect the constitutive expression of transforming growth factor β mRNA, indicating that IFNγ did not induce general degradation of mRNAs. Run-on experiments indicated that c-fos was constitutively transcribed at low levels and that TPA augmented c-fos transcription. IFNγ did not inhibit constitutive or TPA-induced c-fos transcription. However, IFNγ decreased c-fos mRNA stability, as assessed by measuring the half-life of c-fos mRNA in actinomycin D-treated cells. These results indicated that IFNγ inhibited c-fos mRNA induction by TPA at the posttranscriptional level.