Structure of mouse interferon stimulated gene factor 3 gamma (ISGF3 gamma/p48) cDNA and chromosomal localization of the gene.

Interferon stimulated gene factor 3 (ISGF3) is a trimeric transcription factor activated on treatment of cells with interferon-alpha and beta (type I IFNs). Upon stimulation, the regulatory subunits, p84/91 and p113, present in the cytoplasm are phosphorylated at specific tyrosine residues and assemble with the DNA binding subunit, ISGF3 gamma, into the active ISGF3 in the nucleus. Thus, ISGF3 plays a primary role in the transmission of a signal from the cell surface to the nucleus. In this report, we describe the cloning of a mouse cDNA encoding a polypeptide homologous to human ISGF3 gamma. Comparison of the deduced amino acid sequences revealed the middle region was significantly different between mouse and man. The mouse cDNA was shown to encode a functional ISGF3 subunit by means of an in vitro reconstitution assay. Furthermore, the locus of the ISGF3 gamma gene, designated as Isgf3g, was mapped to distal mouse chromosome 14 by linkage analysis using an intersubspecific backcross typing panel.