PARENT SESSION
MECHANISMS OF HORMONE ACTION

Tuesday, August 3, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(353) PREGNANCY AND INTERFERON TAU REGULATE EXPRESSION OF N-MYC INTERACTOR (Nmi) IN THE OVINE UTERUS.

Song, Gwonhwa¹, Fleming, Jo-Ann¹, Bazer, Fuller¹, Spencer, Thomas¹, ¹ Texas A&M University, College Station, TX

ABSTRACT- N-Myc interactor (Nmi) is an interferon (IFN)-inducible gene that interacts with transcription factors containing a Zip, HLH, or HLH-Zip motif (N-Myc or C-Myc) and Stat proteins, except Stat2. Nmi augments Stat-mediated transcription by enhancing their association with the cointegrator CBP/p300. Ovine conceptus trophectoderm produces IFN from Days 11 to 20, which acts on the endometrium to simultaneously inhibit development of the luteolytic mechanism and stimulate transcription of IFN-stimulated genes. Microarray analysis of human 2fTGH cells identified Nmi as an IFN-stimulated gene. In Study One, ewes were hysterectomized between Days 10 and 16 of the estrous cycle (C) or Days 10 and 20 of pregnancy (Px). Endometrial Nmi mRNA levels were not affected by day of the estrous cycle, but increased between Days 12 and 16 in Px ewes. In C ewes, Nmi mRNA was detected at low levels in endometrial lumenal (LE) and glandular (GE) epithelia, and stroma (S). On Days 14 to 20 of Px, Nmi mRNA expression increased markedly in S and GE and moderately in LE. In Study Two, cyclic ewes were ovariectomized and fitted with intrauterine (i.u.) catheters on Day 5 and treated daily with progesterone (P) (Days 5-16, i.m.), ZK 137.316 (a P receptor antagonist; Days 11-16, i.m.), or protein (Days 11-16, i.u.) as follows: (1) P and control proteins (CX, Days 11-16) [P+CX]; (2) P and recombinant ovine IFN [P+IFN]; (3) P and ZK and CX proteins [P+ZK+CX]; and (4) P+ZK and IFN [P+ZK+IFN]. All ewes were hysterectomized on Day 17. Endometrial Nmi mRNA levels were 2.5-fold greater (P<0.01) in P+IFN vs P+CX and in P+ZK+IFN vs P+ZK+CX ewes. In IFN-infused ewes, Nmi mRNA was increased primarily in S and GE with lower levels in LE. In Study 3, parental 2fTGH and U3A (Stat1-deficient) cells were treated with IFN for 0, 6, 12 or 24 h. Western blot analyses of whole cell extracts detected Nmi protein (38.5 kDa) in both cell lines, but Nmi protein increased in response to IFN only in 2fTGH cells. Thus, IFN from the conceptus acts in a paracrine manner to stimulate expression of Nmi in all endometrial cell types. Nmi is proposed to enhance transcription of endometrial genes important for pregnancy by augmenting recruitment of coactivator proteins to transcription factors involved in the signaling pathway of IFN and other hormones/cytokines. Supported by NIH Grant HD32534.

KEY WORDS: uterus, ovine, interferon, n-myc interactor