Interferon regulatory factor-two restricts expression of interferon-stimulated genes to the endometrial stroma and glandular epithelium of the ovine uterus

Interferon tau (IFN tau) is the signal for maternal recognition of pregnanc y in ruminants. The positive effects of IFN tau on IFN-stimulated gene (ISG ) expression are mediated by ISG factor 3 (ISGF3), which is composed of sig nal transducer and activator of transcription (Stat) 1, Stat 2, and IFN reg ulatory factor-9 (IRF-9), and by gamma-activated factor (GAF), which is a S tat 1 homodimer. induction of ISGs, such as ISGs, and 2',5'-oligoadenylate synthetase, by IFN tau during pregnancy is limited to the endometrial strom a (S) and glandular epithelium (GE) of the ovine uterus. The IRF-2, a poten t transcriptional repressor of ISG expression, is expressed in the luminal epithelium (LE). This study determined effects of the estrous cycle, pregna ncy, and IFN tau on expression of Stat 1, Stat 2, IRF-9, IRF-1, and IRF-2 g enes in the ovine endometrium. in cyclic ewes, Stat 1, Stat 2, IRF-1, and I RF-9 mRNA and protein were detected at low levels in the S and GE. During p regnancy, expression of these genes increased only in the S and GE. Express ion of IRF-2 was detected only in the LE and superficial GE (sGE) of both c yclic and pregnant ewes. in cyclic ewes, intrauterine administration of IFN tau stimulated Stat 1, Stat 2, IRF-9, and IRF-1 expression in the endometr ium. Ovine IRF-2 repressed transcriptional activity driven by IFN-stimulate d response elements that bind ISGF3, but not by gamma-activation sequences that bind GAR These results suggest that IRF-2 in the LE and sGE restricts IFN tau induction of ISGs to the S and GE. In the S and GE, IFN tau hyperac tivation of ISG expression likely involves formation and actions of the tra nscription factors ISGF3 and, perhaps, IRF-1.