The regulatory region and transcription factor required for the expression of rat and salmon pituitary hormone-encoding genes show cell-type and species specificity.

The promoter regions of the genes encoding the rat and chum salmon growth hormones (GH) and rat prolactin (PRL) were combined with a reporter gene and introduced into GH- and/or PRL-producing cells from rat. The rat GH and PRL promoters (pGH and pPRL, respectively) were most active in cells producing GH and PRL, respectively. The activity of the salmon pGH was much less than that of the rat pGH in rat GH-producing cells. The regulatory region required for cell-type-specific gene expression of pituitary hormones thus contains information, not only for cell-type specificity, but possibly for species specificity as well. A reporter plasmid containing the GH or somatolactin (SL) promoter and an effector plasmid having a gene encoding transcription factor Pit-1 (rat or salmon) were cotransfected into HeLa (human) or EPC (carp) cells. Rat and salmon Pit-1 were more active in HeLa and EPC cells, respectively, indicating that Pit-1 appears to interact species specifically with the transcription machinery.