Mouse oviduct-specific glycoprotein gene:: Genomic organization and structure of the 5′-flanking regulatory region

A member of the chitinase protein family, oviduct-specific glycoprotein (OGP), can directly associate with gametes or with the early embryo in the oviduct. Although the glycoprotein is widely distributed among mammalian species and there is indirect evidence concerning the involvement of the molecule in the fertilization process, its physiological functions are far from completely understood. To understand the fundamental mechanisms that direct gene expression as well as to know the physiological significance of OGP, we have isolated and characterized a mouse OGP gene (mogp-1). The gene was found to span 13.4 kilobases (kb) including 11 exons and 10 introns. The genomic organization of mogp-1 is well conserved compared to the other members of the chitinase family. Two transcription initiation sites were found at positions 18 and 14 upstream from the first ATG codon. Fluorescence in situ hybridization analysis demonstrated that the mogp-1 was located on the R-positive F3 band of mouse chromosome 3. Although the putative promoter region of mogp-1 lacked typical TATA, CAAT, or GC box sequences, the region contained several motif sequences of transcription factor binding sites including 10 half-palindromic estrogen responsive elements (ERE) and an imperfect ERE. Transient transfection experiments demonstrated that promoter activity could be modulated by various sequences within the 2.2 kb of the 5'-flanking region, and that the mogp-1 promoter was transactivated in an estrogen receptor-positive cell line, MCF-7, by the addition of estradiol-17 beta (E-2). In addition, relevant promoter activity for E-2 responsiveness resides within the first 270 base pairs upstream of the mogp-1. These findings should facilitate our understanding of the regulation of OGP gene expression, and they may be helpful for designing experiments to unravel the role of OGP in the process of mammalian fertilization.