A gene encoding chinook salmon (Oncorhynchus tschawytscha) prolactin: gene structure and potential cis-acting regulatory elements.

A full-length chinook salmon (Oncorhynchus tschawytscha) prolactin (PRL) gene, the first genomic clone of a teleost prolactin, was isolated and fully sequenced. The chinook PRL genomic sequence spans 6.4 Kb, including 2.4 Kb of 5' flanking sequence, 3.0 Kb representing the five exons and four introns of the complete PRL gene, and 0.9 Kb of 3' flanking sequence. The transcriptional start site of the PRL gene was mapped through the agreement of both primer extension and S1 nuclease protection assay. The 5' flanking region of the PRL gene was searched for potential cis-acting elements based on the consensus binding site of trans-acting factor Pit-1, known to be involved in PRL gene expression in mammals. Functional analysis of PRL promoter by the transient transfection of several PRL promoter/CAT chimeric plasmids into rainbow trout pituitary cells suggests a functional PRL promoter whose cell-specific activity is most likely governed by both positive and negative mechanisms.