Isolation and Structure of the Gene for the Progesterone-inducible Protein Uteroglobin

Uteroglobin is a small steroid-binding protein that is differentially regulated by steroid hormones in several tissues of the rabbit. In endometrium, the levels of uteroglobin mRNA increase after progesterone administration due to an enhanced rate of transcription of the uteroglobin gene. As a prerequisite for understanding the molecular mechanisms that modulate uteroglobin gene expression, we have isolated and characterized the uteroglobin gene. We first synthesized, cloned, and sequenced a uteroglobin cDNA that was used to screen a rabbit gene library and to show that the uteroglobin gene is not reiterated in the rabbit genome. We obtained three recombinant phages containing uteroglobin gene sequences and covering 35 kilobases of the rabbit genome. The uteroglobin gene is 3 kilobases long and is composed of three short exons separated by a long and a short intron. The complete coding sequence, the short intron, part of the large intron, and the flanking sequences have been subjected to sequence analysis. The salient features of the nucleotide sequence, including the absence of a canonical "T-A-T-A box," are discussed. A possible relationship is considered between the exon-intron structure of the gene and the known structure and function of uteroglobin.