The gene structure of rat androgen-binding protein: identification of potential regulatory deoxyribonucleic acid elements of a follicle-stimulating hormone-regulated protein.

Abstract

A genomic clone has been characterized for androgen-binding protein (ABP), a Sertoli cell secretory protein that is regulated by androgens and FSH. A 5.3-kilobase pair Sstl DNA fragment was sequenced and found to contain the entire coding region of the gene, which is divided into 8 exons. The major transcription initiation site in the testis was localized by primer extension with two unique oligomers. In addition, a minor initiation site was identified that appears to originate from another promoter. The gene does not contain a conventional TATA box immediately upstream from the major start site; rather, the sequence TACCTA occurs at residue -24. This sequence has been described functionally as a TATA-like element in the SV40 major late gene. Other potential regulatory elements include a sequence related to the cAMP response element at residue -126 base pair. Using primary Sertoli cell cultures, it was found that (Bu)2cAMP or FSH increases ABP mRNA levels 3-5 fold, with a 2-fold increase in the level of secreted ABP. Southern blot analysis of rat genomic DNA indicated that there is a single gene for ABP in the rat. The existence of one gene supports the idea that sex hormone binding globulin produced by fetal rat liver is coded by the same gene.