Kj. Austin et al., UBIQUITIN CROSS-REACTIVE PROTEIN IS RELEASED BY THE BOVINE UTERUS IN RESPONSE TO INTERFERON DURING EARLY-PREGNANCY, Biology of reproduction, 54(3), 1996, pp. 600-606
A 16-kDa protein has been identified that is secreted by the bovine en
dometrium in response to conceptus-derived interferon (IFN)-tau during
early pregnancy. Because this uterine protein was similar in size to
a human ubiquitin cross-reactive protein (hUCRP) that also was regulat
ed by IFN, we suspected that they might be related. To test this hypot
hesis, uterine flushings, medium from cultured endometrium, and endome
trial tissues were examined for the presence of ubiquitin-immunoreacti
ve proteins. Immunoreacting proteins were detected through use of one-
dimensional (1D)-PAGE and Western blotting with ubiquitin and hUCRP an
tiserum (1:500). A 16-kDa protein that cross-reacted with ubiquitin an
d hUCRP antisera was released by the endometrium and was present in ut
erine flushings from all Day 18 pregnant females examined (n = 12). Th
e immunoreacting 16-kDa protein was absent in all nonpregnant females
examined (n = 23), Regulation of this uterine protein by recombinant t
ype I IFNs (rbIFN-tau, rbIFN-alpha, and roIFN-tau), using 0, 0.5, 5, a
nd 25 nm of each IFN, was evaluated in nonpregnant (Day 12) heifers (n
= 5) using 1D-PAGE and Western blotting. Release of the 16-kDa protei
n into medium was negligible in controls (0 nm IFN). For each IFN, a d
ose-dependent increase (p < 0.05) in release of the immunoreacting 16-
kDa protein was noted. We conclude that the 16-kDa protein that is pro
duced by the endometrium in response to IFN-tau during early pregnancy
also shares epitopes with hUCRP and ubiquitin. The 16-kDa protein has
been named bovine UCRP.