Interferon Regulatory Factor-Two Restricts Expression of Interferon-Stimulated Genes to the Endometrial Stroma and Glandular Epithelium of the Ovine Uterus1

Abstract

Interferon tau (IFNtau) is the signal for maternal recognition of pregnancy in ruminants. The positive effects of IFNtau on IFN-stimulated gene (ISG) expression are mediated by ISG factor 3 (ISGF3), which is composed of signal transducer and activator of transcription (Stat) 1, Stat 2, and IFN regulatory factor-9 (IRF-9), and by gamma-activated factor (GAF), which is a Stat 1 homodimer. Induction of ISGs, such as ISG17 and 2',5'-oligoadenylate synthetase, by IFNtau during pregnancy is limited to the endometrial stroma (S) and glandular epithelium (GE) of the ovine uterus. The IRF-2, a potent transcriptional repressor of ISG expression, is expressed in the luminal epithelium (LE). This study determined effects of the estrous cycle, pregnancy, and IFNtau on expression of Stat 1, Stat 2, IRF-9, IRF-1, and IRF-2 genes in the ovine endometrium. In cyclic ewes, Stat 1, Stat 2, IRF-1, and IRF-9 mRNA and protein were detected at low levels in the S and GE. During pregnancy, expression of these genes increased only in the S and GE. Expression of IRF-2 was detected only in the LE and superficial GE (sGE) of both cyclic and pregnant ewes. In cyclic ewes, intrauterine administration of IFNtau stimulated Stat 1, Stat 2, IRF-9, and IRF-1 expression in the endometrium. Ovine IRF-2 repressed transcriptional activity driven by IFN-stimulated response elements that bind ISGF3, but not by gamma-activation sequences that bind GAF. These results suggest that IRF-2 in the LE and sGE restricts IFNtau induction of ISGs to the S and GE. In the S and GE, IFNtau hyperactivation of ISG expression likely involves formation and actions of the transcription factors ISGF3 and, perhaps, IRF-1.

Suppressor of cytokine signalling (SOCS) genes are expressed in the endometrium and regulated by conceptus signals during early pregnancy in the ewe

“…The expression of the SOCSs 1, 2 and 3 mRNA was stimulated by a single intrauterine injection of roIFN in cyclic ewes after 2 h. This stimulation is rapid and transient as expected from what was reported in other biological systems where SOCS are known as cytokineinducible immediate early genes (Yoshimura et al 1995, Endo et al 1997, Krebs & Hilton 2000. The SOCSs 1, 2 and 3 mRNA levels were induced in the caruncles, consistent with the expression of both ovine type I IFNAR subunits in these endometrium zones (Rosenfeld et al 2002) as well as the expression of IRF-1 and various STAT proteins (Choi et al 2001, all required for the induction of SOCS genes (Krebs & Hilton 2000, Fujimoto & Naka 2003. Taken together, these data suggest that SOCSs 1, 2 and 3 are IFN target genes as formerly reported in human T-cells for IFN , another member of the type I IFN family (Brender et al 2001).…”

Implantation mechanisms: insights from the sheep

“…Progesterone induced and IFNt increased galectin-15 mRNA in the endometrium. Thus, galectin-15 and Wnt7a are the only genes currently known to be increased by IFNt in the endometrial LE of the ovine uterus (Choi et al 2001, Kim et al 2003, Gray et al 2004.…”

Galectin-15 in ovine uteroplacental tissues

“…For each ewe, denatured total cellular RNA (20 mg) was analyzed by slot-blot hybridization using a radiolabeled antisense cRNA probe generated by in vitro transcription with [a-32 P]UTP (Amersham Pharmacia Biotech, Piscataway, NJ, USA) as described previously (Gray et al 2004). Plasmid templates containing cDNAs for ovine galectin-15 (Gray et al 2004) and 18 S rRNA (pT718S; Ambion, Austin, TX) were used to produce radiolabeled cRNA probes as described previously (Choi et al 2001). Hybridization signals were detected by exposing washed slot blots to a phosphorimager screen and visualized and quantified using a Typhoon 8600 Variable Mode Imager (Molecular Dynamics, Sunnyvale, CA, USA).…”