Molecular cloning and in vivo expression of the bovine steroidogenic acute regulatory protein

Differential screening was used to select clones from a bovine luteal cDNA library, which were specifically expressed in late luteal stages. One of these clones encoded the bovine homologue of the Steroidogenic Acute Regulatory protein (StAR). The bovine StAR gene is transcribed as 3kb and 1.8kb transcripts, which differ in their sites of 3' polyadenylation. Both transcripts are highly expressed in corpora lutea of mid to late cycle and through pregnancy, but only at low levels in the early cycle. Northern analysis showed expression only in the corpus luteum and in the adrenal gland, but not in any other tissue examined. Within the protein coding region of the bovine StAR gene, there is a marked 124 base homology to the 5' non-coding region of another luteal transcript, TIMP-1, suggesting a possible common regulatory function for this sequence.