An interferon-induced mx protein: cDNA sequence and high-level expression in the endometrium of pregnant sheep

We have cloned a 2.4-kb cDNA containing the complete coding sequence of ovine Mx from a lambda ZAP library constructed using RNA from the endometrium of a normal sheep on day 16 of pregnancy. Ovine Mx shows 80% similarity to human MxA. Human and mouse Mx are type-1 interferon (IFN)-induced genes that have previously been shown to confer resistance to influenza virus. The ovine Mx cDNA contains an open reading frame of 1962 nucleotides (nt) coding for a 653-amino-acid (aa) protein. The deduced translated sequence has consensus GTP-binding sites and similarity to the human MxA sequence (RKFLKERLARL) that has been shown to be essential for resistance against vesicular stomatitis virus (VSV). The presence of Mx mRNA was investigated by Northern blot analysis in the endometrium of non-pregnant sheep and between days 8 and 127 of pregnancy. Mx expression was detected at high levels between day 13 and day 20 of pregnancy. Furthermore, eightfold higher levels of Mx mRNA were detected in the pregnant versus the non-pregnant uterine horn in unilaterally pregnant sheep. Mx mRNA can be induced in sheep endometrium by ovine trophoblast interferon (IFN-tau).