The Leydig insulin-like peptide

We have isolated and sequenced the cDNA and gene coding for a novel member of the insulin-like hormone superfamily. The gene is expressed exclusively in prenatal and postnatal Leydig cells and in postnatal ovary. We have tentatively proposed the name Leydig insulin-like (Ley I-L) for the gene and its encoded protein. The porcine Leydig insulin-like protein is synthesized as a 131-amino acid preproprotein, which contains a 24 amino acid signal peptide. Comparison of the deduced amino acid sequence of pro-leydig insulin-like protein predicts that the biologically active protein, after proteolytic processing of the C-peptide, consists of a 32 residue-long B-chain and a 26-residue-long A-chain. Western blot analyses with antiserum against a synthetic oligopeptide containing the amino acid sequence of the B-chain confirm the proteolytic processing of the pro-ley I-L peptide. Furthermore, we describe here the initial analysis of the Ley I-L gene promoter by transient gene transfer studies. We show that the sequence between -186 and +13 of the porcine Ley I-L gene contains sufficient information to direct preferential expression of the chloramphenicol-acetyltransferase (CAT) reporter gene in Leydig cells and sequences important for negative regulation of Ley I-L promoter activity are contained in the region between -960 and -186.