Estradiol up-regulates expression of the A + U-rich binding factor 1 (AUF1) gene in the sheep uterus

The A+U-rich binding factor 1 (AUF1 or HNRPD) gene produces predominant RNA binding proteins. The AUF1 transcript is alternatively spliced to produce four protein isoforms that stabilize or destabilize hundreds of mRNAs. Previously, we discovered that estradiol (E2) treatment of ovariectomized sheep increased concentrations of AUF1p45 protein which stabilized estrogen receptor alpha (ER) mRNA in the uterus. This study examined E2 regulation of AUF1 mRNAs in the sheep uterus. Northern analysis determined that E2 treatment increased concentrations of total AUF1 mRNAs twofold in endometrial and myometrial tissue compartments. In situ hybridization indicated that the increase was most intense in the glandular epithelium of endometrium. In a well characterized in vitro RNA stability assay, AUF1 3'UTR sequences were much more stable in uterine extracts from E2-treated ewes compared to extracts from control ewes. AUF1 mRNAs with alternative splicing of exons 2 and 7 (in the coding sequence) and exon 9 (in the 3'UTR) were identified. The only effect of E2 treatment on alternative splicing was that it reduced the percentage of AUF1 mRNAs containing exon 9-derived sequences. These data indicate that E2 up-regulates AUF1 and ER genes coordinately by a post-transcriptional mechanism.